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diff --git a/lib/diameter/doc/standard/rfc7683.txt b/lib/diameter/doc/standard/rfc7683.txt new file mode 100644 index 0000000000..ab2392c6c0 --- /dev/null +++ b/lib/diameter/doc/standard/rfc7683.txt @@ -0,0 +1,2355 @@ + + + + + + +Internet Engineering Task Force (IETF) J. Korhonen, Ed. +Request for Comments: 7683 Broadcom Corporation +Category: Standards Track S. Donovan, Ed. +ISSN: 2070-1721 B. Campbell + Oracle + L. Morand + Orange Labs + October 2015 + + + Diameter Overload Indication Conveyance + +Abstract + + This specification defines a base solution for Diameter overload + control, referred to as Diameter Overload Indication Conveyance + (DOIC). + +Status of This Memo + + This is an Internet Standards Track document. + + This document is a product of the Internet Engineering Task Force + (IETF). It represents the consensus of the IETF community. It has + received public review and has been approved for publication by the + Internet Engineering Steering Group (IESG). Further information on + Internet Standards is available in Section 2 of RFC 5741. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + http://www.rfc-editor.org/info/rfc7683. + +Copyright Notice + + Copyright (c) 2015 IETF Trust and the persons identified as the + document authors. All rights reserved. + + This document is subject to BCP 78 and the IETF Trust's Legal + Provisions Relating to IETF Documents + (http://trustee.ietf.org/license-info) in effect on the date of + publication of this document. Please review these documents + carefully, as they describe your rights and restrictions with respect + to this document. Code Components extracted from this document must + include Simplified BSD License text as described in Section 4.e of + the Trust Legal Provisions and are provided without warranty as + described in the Simplified BSD License. + + + + + +Korhonen, et al. Standards Track [Page 1] + +RFC 7683 DOIC October 2015 + + +Table of Contents + + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 + 2. Terminology and Abbreviations . . . . . . . . . . . . . . . . 3 + 3. Conventions Used in This Document . . . . . . . . . . . . . . 5 + 4. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 5 + 4.1. Piggybacking . . . . . . . . . . . . . . . . . . . . . . 6 + 4.2. DOIC Capability Announcement . . . . . . . . . . . . . . 7 + 4.3. DOIC Overload Condition Reporting . . . . . . . . . . . . 9 + 4.4. DOIC Extensibility . . . . . . . . . . . . . . . . . . . 11 + 4.5. Simplified Example Architecture . . . . . . . . . . . . . 12 + 5. Solution Procedures . . . . . . . . . . . . . . . . . . . . . 12 + 5.1. Capability Announcement . . . . . . . . . . . . . . . . . 12 + 5.1.1. Reacting Node Behavior . . . . . . . . . . . . . . . 13 + 5.1.2. Reporting Node Behavior . . . . . . . . . . . . . . . 13 + 5.1.3. Agent Behavior . . . . . . . . . . . . . . . . . . . 14 + 5.2. Overload Report Processing . . . . . . . . . . . . . . . 15 + 5.2.1. Overload Control State . . . . . . . . . . . . . . . 15 + 5.2.2. Reacting Node Behavior . . . . . . . . . . . . . . . 19 + 5.2.3. Reporting Node Behavior . . . . . . . . . . . . . . . 20 + 5.3. Protocol Extensibility . . . . . . . . . . . . . . . . . 22 + 6. Loss Algorithm . . . . . . . . . . . . . . . . . . . . . . . 23 + 6.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 23 + 6.2. Reporting Node Behavior . . . . . . . . . . . . . . . . . 24 + 6.3. Reacting Node Behavior . . . . . . . . . . . . . . . . . 24 + 7. Attribute Value Pairs . . . . . . . . . . . . . . . . . . . . 25 + 7.1. OC-Supported-Features AVP . . . . . . . . . . . . . . . . 25 + 7.2. OC-Feature-Vector AVP . . . . . . . . . . . . . . . . . . 25 + 7.3. OC-OLR AVP . . . . . . . . . . . . . . . . . . . . . . . 26 + 7.4. OC-Sequence-Number AVP . . . . . . . . . . . . . . . . . 26 + 7.5. OC-Validity-Duration AVP . . . . . . . . . . . . . . . . 26 + 7.6. OC-Report-Type AVP . . . . . . . . . . . . . . . . . . . 27 + 7.7. OC-Reduction-Percentage AVP . . . . . . . . . . . . . . . 27 + 7.8. AVP Flag Rules . . . . . . . . . . . . . . . . . . . . . 28 + 8. Error Response Codes . . . . . . . . . . . . . . . . . . . . 28 + 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 + 9.1. AVP Codes . . . . . . . . . . . . . . . . . . . . . . . . 29 + 9.2. New Registries . . . . . . . . . . . . . . . . . . . . . 29 + 10. Security Considerations . . . . . . . . . . . . . . . . . . . 30 + 10.1. Potential Threat Modes . . . . . . . . . . . . . . . . . 30 + 10.2. Denial-of-Service Attacks . . . . . . . . . . . . . . . 31 + 10.3. Noncompliant Nodes . . . . . . . . . . . . . . . . . . . 32 + 10.4. End-to-End Security Issues . . . . . . . . . . . . . . . 32 + 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 34 + 11.1. Normative References . . . . . . . . . . . . . . . . . . 34 + 11.2. Informative References . . . . . . . . . . . . . . . . . 34 + + + + + +Korhonen, et al. Standards Track [Page 2] + +RFC 7683 DOIC October 2015 + + + Appendix A. Issues Left for Future Specifications . . . . . . . 35 + A.1. Additional Traffic Abatement Algorithms . . . . . . . . . 35 + A.2. Agent Overload . . . . . . . . . . . . . . . . . . . . . 35 + A.3. New Error Diagnostic AVP . . . . . . . . . . . . . . . . 35 + Appendix B. Deployment Considerations . . . . . . . . . . . . . 35 + Appendix C. Considerations for Applications Integrating the DOIC + Solution . . . . . . . . . . . . . . . . . . . . . . 36 + C.1. Application Classification . . . . . . . . . . . . . . . 36 + C.2. Implications of Application Type Overload . . . . . . . . 37 + C.3. Request Transaction Classification . . . . . . . . . . . 38 + C.4. Request Type Overload Implications . . . . . . . . . . . 39 + Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 41 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 42 + +1. Introduction + + This specification defines a base solution for Diameter overload + control, referred to as Diameter Overload Indication Conveyance + (DOIC), based on the requirements identified in [RFC7068]. + + This specification addresses Diameter overload control between + Diameter nodes that support the DOIC solution. The solution, which + is designed to apply to existing and future Diameter applications, + requires no changes to the Diameter base protocol [RFC6733] and is + deployable in environments where some Diameter nodes do not implement + the Diameter overload control solution defined in this specification. + + A new application specification can incorporate the overload control + mechanism specified in this document by making it mandatory to + implement for the application and referencing this specification + normatively. It is the responsibility of the Diameter application + designers to define how overload control mechanisms work on that + application. + + Note that the overload control solution defined in this specification + does not address all the requirements listed in [RFC7068]. A number + of features related to overload control are left for future + specifications. See Appendix A for a list of extensions that are + currently being considered. + +2. Terminology and Abbreviations + + Abatement + + Reaction to receipt of an overload report resulting in a reduction + in traffic sent to the reporting node. Abatement actions include + diversion and throttling. + + + + +Korhonen, et al. Standards Track [Page 3] + +RFC 7683 DOIC October 2015 + + + Abatement Algorithm + + An extensible method requested by reporting nodes and used by + reacting nodes to reduce the amount of traffic sent during an + occurrence of overload control. + + Diversion + + An overload abatement treatment where the reacting node selects + alternate destinations or paths for requests. + + Host-Routed Requests + + Requests that a reacting node knows will be served by a particular + host, either due to the presence of a Destination-Host Attribute + Value Pair (AVP) or by some other local knowledge on the part of + the reacting node. + + Overload Control State (OCS) + + Internal state maintained by a reporting or reacting node + describing occurrences of overload control. + + Overload Report (OLR) + + Overload control information for a particular overload occurrence + sent by a reporting node. + + Reacting Node + + A Diameter node that acts upon an overload report. + + Realm-Routed Requests + + Requests sent by a reacting node where the reacting node does not + know to which host the request will be routed. + + Reporting Node + + A Diameter node that generates an overload report. (This may or + may not be the overloaded node.) + + + + + + + + + + +Korhonen, et al. Standards Track [Page 4] + +RFC 7683 DOIC October 2015 + + + Throttling + + An abatement treatment that limits the number of requests sent by + the reacting node. Throttling can include a Diameter Client + choosing to not send requests, or a Diameter Agent or Server + rejecting requests with appropriate error responses. In both + cases, the result of the throttling is a permanent rejection of + the transaction. + +3. Conventions Used in This Document + + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this + document are to be interpreted as described in RFC 2119 [RFC2119]. + + The interpretation from RFC 2119 [RFC2119] does not apply for the + above listed words when they are not used in all caps. + +4. Solution Overview + + The Diameter Overload Information Conveyance (DOIC) solution allows + Diameter nodes to request that other Diameter nodes perform overload + abatement actions, that is, actions to reduce the load offered to the + overloaded node or realm. + + A Diameter node that supports DOIC is known as a "DOIC node". Any + Diameter node can act as a DOIC node, including Diameter Clients, + Diameter Servers, and Diameter Agents. DOIC nodes are further + divided into "Reporting Nodes" and "Reacting Nodes." A reporting + node requests overload abatement by sending Overload Reports (OLRs). + + A reacting node acts upon OLRs and performs whatever actions are + needed to fulfill the abatement requests included in the OLRs. A + reporting node may report overload on its own behalf or on behalf of + other nodes. Likewise, a reacting node may perform overload + abatement on its own behalf or on behalf of other nodes. + + A Diameter node's role as a DOIC node is independent of its Diameter + role. For example, Diameter Agents may act as DOIC nodes, even + though they are not endpoints in the Diameter sense. Since Diameter + enables bidirectional applications, where Diameter Servers can send + requests towards Diameter Clients, a given Diameter node can + simultaneously act as both a reporting node and a reacting node. + + Likewise, a Diameter Agent may act as a reacting node from the + perspective of upstream nodes, and a reporting node from the + perspective of downstream nodes. + + + + +Korhonen, et al. Standards Track [Page 5] + +RFC 7683 DOIC October 2015 + + + DOIC nodes do not generate new messages to carry DOIC-related + information. Rather, they "piggyback" DOIC information over existing + Diameter messages by inserting new AVPs into existing Diameter + requests and responses. Nodes indicate support for DOIC, and any + needed DOIC parameters, by inserting an OC-Supported-Features AVP + (Section 7.1) into existing requests and responses. Reporting nodes + send OLRs by inserting OC-OLR AVPs (Section 7.3). + + A given OLR applies to the Diameter realm and application of the + Diameter message that carries it. If a reporting node supports more + than one realm and/or application, it reports independently for each + combination of realm and application. Similarly, the OC-Supported- + Features AVP applies to the realm and application of the enclosing + message. This implies that a node may support DOIC for one + application and/or realm, but not another, and may indicate different + DOIC parameters for each application and realm for which it supports + DOIC. + + Reacting nodes perform overload abatement according to an agreed-upon + abatement algorithm. An abatement algorithm defines the meaning of + some of the parameters of an OLR and the procedures required for + overload abatement. An overload abatement algorithm separates + Diameter requests into two sets. The first set contains the requests + that are to undergo overload abatement treatment of either throttling + or diversion. The second set contains the requests that are to be + given normal routing treatment. This document specifies a single + "must-support" algorithm, namely, the "loss" algorithm (Section 6). + Future specifications may introduce new algorithms. + + Overload conditions may vary in scope. For example, a single + Diameter node may be overloaded, in which case, reacting nodes may + attempt to send requests to other destinations. On the other hand, + an entire Diameter realm may be overloaded, in which case, such + attempts would do harm. DOIC OLRs have a concept of "report type" + (Section 7.6), where the type defines such behaviors. Report types + are extensible. This document defines report types for overload of a + specific host and for overload of an entire realm. + + DOIC works through non-supporting Diameter Agents that properly pass + unknown AVPs unchanged. + +4.1. Piggybacking + + There is no new Diameter application defined to carry overload- + related AVPs. The overload control AVPs defined in this + specification have been designed to be piggybacked on top of existing + + + + + +Korhonen, et al. Standards Track [Page 6] + +RFC 7683 DOIC October 2015 + + + application messages. This is made possible by adding the optional + overload control AVPs OC-OLR and OC-Supported-Features into existing + commands. + + Reacting nodes indicate support for DOIC by including the + OC-Supported-Features AVP in all request messages originated or + relayed by the reacting node. + + Reporting nodes indicate support for DOIC by including the + OC-Supported-Features AVP in all answer messages that are originated + or relayed by the reporting node and that are in response to a + request that contained the OC-Supported-Features AVP. Reporting + nodes may include overload reports using the OC-OLR AVP in answer + messages. + + Note that the overload control solution does not have fixed server + and client roles. The DOIC node role is determined based on the + message type: whether the message is a request (i.e., sent by a + "reacting node") or an answer (i.e., sent by a "reporting node"). + Therefore, in a typical client-server deployment, the Diameter Client + may report its overload condition to the Diameter Server for any + Diameter-Server-initiated message exchange. An example of such is + the Diameter Server requesting a re-authentication from a Diameter + Client. + +4.2. DOIC Capability Announcement + + The DOIC solution supports the ability for Diameter nodes to + determine if other nodes in the path of a request support the + solution. This capability is referred to as DOIC Capability + Announcement (DCA) and is separate from the Diameter Capability + Exchange. + + The DCA mechanism uses the OC-Supported-Features AVPs to indicate the + Diameter overload features supported. + + The first node in the path of a Diameter request that supports the + DOIC solution inserts the OC-Supported-Features AVP in the request + message. + + The individual features supported by the DOIC nodes are indicated in + the OC-Feature-Vector AVP. Any semantics associated with the + features will be defined in extension specifications that introduce + the features. + + Note: As discussed elsewhere in the document, agents in the path + of the request can modify the OC-Supported-Features AVP. + + + + +Korhonen, et al. Standards Track [Page 7] + +RFC 7683 DOIC October 2015 + + + Note: The DOIC solution must support deployments where Diameter + Clients and/or Diameter Servers do not support the DOIC solution. + In this scenario, Diameter Agents that support the DOIC solution + may handle overload abatement for the non-supporting Diameter + nodes. In this case, the DOIC agent will insert the OC-Supported- + Features AVP in requests that do not already contain one, telling + the reporting node that there is a DOIC node that will handle + overload abatement. For transactions where there was an + OC-Supporting-Features AVP in the request, the agent will insert + the OC-Supported-Features AVP in answers, telling the reacting + node that there is a reporting node. + + The OC-Feature-Vector AVP will always contain an indication of + support for the loss overload abatement algorithm defined in this + specification (see Section 6). This ensures that a reporting node + always supports at least one of the advertised abatement algorithms + received in a request messages. + + The reporting node inserts the OC-Supported-Features AVP in all + answer messages to requests that contained the OC-Supported-Features + AVP. The contents of the reporting node's OC-Supported-Features AVP + indicate the set of Diameter overload features supported by the + reporting node. This specification defines one exception -- the + reporting node only includes an indication of support for one + overload abatement algorithm, independent of the number of overload + abatement algorithms actually supported by the reacting node. The + overload abatement algorithm indicated is the algorithm that the + reporting node intends to use should it enter an overload condition. + Reacting nodes can use the indicated overload abatement algorithm to + prepare for possible overload reports and must use the indicated + overload abatement algorithm if traffic reduction is actually + requested. + + Note that the loss algorithm defined in this document is a + stateless abatement algorithm. As a result, it does not require + any actions by reacting nodes prior to the receipt of an overload + report. Stateful abatement algorithms that base the abatement + logic on a history of request messages sent might require reacting + nodes to maintain state in advance of receiving an overload report + to ensure that the overload reports can be properly handled. + + While it should only be done in exceptional circumstances and not + during an active occurrence of overload, a reacting node that wishes + to transition to a different abatement algorithm can stop advertising + support for the algorithm indicated by the reporting node, as long as + support for the loss algorithm is always advertised. + + + + + +Korhonen, et al. Standards Track [Page 8] + +RFC 7683 DOIC October 2015 + + + The DCA mechanism must also allow the scenario where the set of + features supported by the sender of a request and by agents in the + path of a request differ. In this case, the agent can update the + OC-Supported-Features AVP to reflect the mixture of the two sets of + supported features. + + Note: The logic to determine if the content of the OC-Supported- + Features AVP should be changed is out of scope for this document, + as is the logic to determine the content of a modified + OC-Supported-Features AVP. These are left to implementation + decisions. Care must be taken not to introduce interoperability + issues for downstream or upstream DOIC nodes. As such, the agent + must act as a fully compliant reporting node to the downstream + reacting node and as a fully compliant reacting node to the + upstream reporting node. + +4.3. DOIC Overload Condition Reporting + + As with DOIC capability announcement, overload condition reporting + uses new AVPs (Section 7.3) to indicate an overload condition. + + The OC-OLR AVP is referred to as an overload report. The OC-OLR AVP + includes the type of report, a sequence number, the length of time + that the report is valid, and AVPs specific to the abatement + algorithm. + + Two types of overload reports are defined in this document: host + reports and realm reports. + + A report of type "HOST_REPORT" is sent to indicate the overload of a + specific host, identified by the Origin-Host AVP of the message + containing the OLR, for the Application-ID indicated in the + transaction. When receiving an OLR of type "HOST_REPORT", a reacting + node applies overload abatement treatment to the host-routed requests + identified by the overload abatement algorithm (as defined in + Section 2) sent for this application to the overloaded host. + + A report of type "REALM_REPORT" is sent to indicate the overload of a + realm for the Application-ID indicated in the transaction. The + overloaded realm is identified by the Destination-Realm AVP of the + message containing the OLR. When receiving an OLR of type + "REALM_REPORT", a reacting node applies overload abatement treatment + to realm-routed requests identified by the overload abatement + algorithm (as defined in Section 2) sent for this application to the + overloaded realm. + + + + + + +Korhonen, et al. Standards Track [Page 9] + +RFC 7683 DOIC October 2015 + + + This document assumes that there is a single source for realm reports + for a given realm, or that if multiple nodes can send realm reports, + that each such node has full knowledge of the overload state of the + entire realm. A reacting node cannot distinguish between receiving + realm reports from a single node or from multiple nodes. + + Note: Known issues exist if there are multiple sources for + overload reports that apply to the same Diameter entity. Reacting + nodes have no way of determining the source and, as such, will + treat them as coming from a single source. Variance in sequence + numbers between the two sources can then cause incorrect overload + abatement treatment to be applied for indeterminate periods of + time. + + Reporting nodes are responsible for determining the need for a + reduction of traffic. The method for making this determination is + implementation specific and depends on the type of overload report + being generated. A host report might be generated by tracking use of + resources required by the host to handle transactions for the + Diameter application. A realm report generally impacts the traffic + sent to multiple hosts and, as such, requires tracking the capacity + of all servers able to handle realm-routed requests for the + application and realm. + + Once a reporting node determines the need for a reduction in traffic, + it uses the DOIC-defined AVPs to report on the condition. These AVPs + are included in answer messages sent or relayed by the reporting + node. The reporting node indicates the overload abatement algorithm + that is to be used to handle the traffic reduction in the + OC-Supported-Features AVP. The OC-OLR AVP is used to communicate + information about the requested reduction. + + Reacting nodes, upon receipt of an overload report, apply the + overload abatement algorithm to traffic impacted by the overload + report. The method used to determine the requests that are to + receive overload abatement treatment is dependent on the abatement + algorithm. The loss abatement algorithm is defined in this document + (Section 6). Other abatement algorithms can be defined in extensions + to the DOIC solution. + + Two types of overload abatement treatment are defined, diversion and + throttling. Reacting nodes are responsible for determining which + treatment is appropriate for individual requests. + + As the conditions that lead to the generation of the overload report + change, the reporting node can send new overload reports requesting + greater reduction if the condition gets worse or less reduction if + the condition improves. The reporting node sends an overload report + + + +Korhonen, et al. Standards Track [Page 10] + +RFC 7683 DOIC October 2015 + + + with a duration of zero to indicate that the overload condition has + ended and abatement is no longer needed. + + The reacting node also determines when the overload report expires + based on the OC-Validity-Duration AVP in the overload report and + stops applying the abatement algorithm when the report expires. + + Note that erroneous overload reports can be used for DoS attacks. + This includes the ability to indicate that a significant reduction in + traffic, up to and including a request for no traffic, should be sent + to a reporting node. As such, care should be taken to verify the + sender of overload reports. + +4.4. DOIC Extensibility + + The DOIC solution is designed to be extensible. This extensibility + is based on existing Diameter-based extensibility mechanisms, along + with the DOIC capability announcement mechanism. + + There are multiple categories of extensions that are expected. This + includes the definition of new overload abatement algorithms, the + definition of new report types, and the definition of new scopes of + messages impacted by an overload report. + + A DOIC node communicates supported features by including them in the + OC-Feature-Vector AVP, as a sub-AVP of OC-Supported-Features. Any + non-backwards-compatible DOIC extensions define new values for the + OC-Feature-Vector AVP. DOIC extensions also have the ability to add + new AVPs to the OC-Supported-Features AVP, if additional information + about the new feature is required. + + Overload reports can also be extended by adding new sub-AVPs to the + OC-OLR AVP, allowing reporting nodes to communicate additional + information about handling an overload condition. + + If necessary, new extensions can also define new AVPs that are not + part of the OC-Supported-Features and OC-OLR group AVPs. It is, + however, recommended that DOIC extensions use the OC-Supported- + Features AVP and OC-OLR AVP to carry all DOIC-related AVPs. + + + + + + + + + + + + +Korhonen, et al. Standards Track [Page 11] + +RFC 7683 DOIC October 2015 + + +4.5. Simplified Example Architecture + + Figure 1 illustrates the simplified architecture for Diameter + overload information conveyance. + + Realm X Same or other Realms + <--------------------------------------> <----------------------> + + + +--------+ : (optional) : + |Diameter| : : + |Server A|--+ .--. : +--------+ : .--. + +--------+ | _( `. : |Diameter| : _( `. +--------+ + +--( )--:-| Agent |-:--( )--|Diameter| + +--------+ | ( ` . ) ) : +--------+ : ( ` . ) ) | Client | + |Diameter|--+ `--(___.-' : : `--(___.-' +--------+ + |Server B| : : + +--------+ : : + + End-to-end Overload Indication + 1) <-----------------------------------------------> + Diameter Application Y + + Overload Indication A Overload Indication A' + 2) <----------------------> <----------------------> + Diameter Application Y Diameter Application Y + + Figure 1: Simplified Architecture Choices for Overload Indication + Delivery + + In Figure 1, the Diameter overload indication can be conveyed (1) + end-to-end between servers and clients or (2) between servers and the + Diameter Agent inside the realm and then between the Diameter Agent + and the clients. + +5. Solution Procedures + + This section outlines the normative behavior for the DOIC solution. + +5.1. Capability Announcement + + This section defines DOIC Capability Announcement (DCA) behavior. + + Note: This specification assumes that changes in DOIC node + capabilities are relatively rare events that occur as a result of + administrative action. Reacting nodes ought to minimize changes + that force the reporting node to change the features being used, + especially during active overload conditions. But even if + + + +Korhonen, et al. Standards Track [Page 12] + +RFC 7683 DOIC October 2015 + + + reacting nodes avoid such changes, reporting nodes still have to + be prepared for them to occur. For example, differing + capabilities between multiple reacting nodes may still force a + reporting node to select different features on a per-transaction + basis. + +5.1.1. Reacting Node Behavior + + A reacting node MUST include the OC-Supported-Features AVP in all + requests. It MAY include the OC-Feature-Vector AVP, as a sub-AVP of + OC-Supported-Features. If it does so, it MUST indicate support for + the "loss" algorithm. If the reacting node is configured to support + features (including other algorithms) in addition to the loss + algorithm, it MUST indicate such support in an OC-Feature-Vector AVP. + + An OC-Supported-Features AVP in answer messages indicates there is a + reporting node for the transaction. The reacting node MAY take + action, for example, creating state for some stateful abatement + algorithm, based on the features indicated in the OC-Feature-Vector + AVP. + + Note: The loss abatement algorithm does not require stateful + behavior when there is no active overload report. + + Reacting nodes need to be prepared for the reporting node to change + selected algorithms. This can happen at any time, including when the + reporting node has sent an active overload report. The reacting node + can minimize the potential for changes by modifying the advertised + abatement algorithms sent to an overloaded reporting node to the + currently selected algorithm and loss (or just loss if it is the + currently selected algorithm). This has the effect of limiting the + potential change in abatement algorithm from the currently selected + algorithm to loss, avoiding changes to more complex abatement + algorithms that require state to operate properly. + +5.1.2. Reporting Node Behavior + + Upon receipt of a request message, a reporting node determines if + there is a reacting node for the transaction based on the presence of + the OC-Supported-Features AVP in the request message. + + If the request message contains an OC-Supported-Features AVP, then a + reporting node MUST include the OC-Supported-Features AVP in the + answer message for that transaction. + + Note: Capability announcement is done on a per-transaction basis. + The reporting node cannot assume that the capabilities announced + by a reacting node will be the same between transactions. + + + +Korhonen, et al. Standards Track [Page 13] + +RFC 7683 DOIC October 2015 + + + A reporting node MUST NOT include the OC-Supported-Features AVP, + OC-OLR AVP, or any other overload control AVPs defined in extension + documents in response messages for transactions where the request + message does not include the OC-Supported-Features AVP. Lack of the + OC-Supported-Features AVP in the request message indicates that there + is no reacting node for the transaction. + + A reporting node knows what overload control functionality is + supported by the reacting node based on the content or absence of the + OC-Feature-Vector AVP within the OC-Supported-Features AVP in the + request message. + + A reporting node MUST select a single abatement algorithm in the + OC-Feature-Vector AVP. The abatement algorithm selected MUST + indicate the abatement algorithm the reporting node wants the + reacting node to use when the reporting node enters an overload + condition. + + The abatement algorithm selected MUST be from the set of abatement + algorithms contained in the request message's OC-Feature-Vector AVP. + + A reporting node that selects the loss algorithm may do so by + including the OC-Feature-Vector AVP with an explicit indication of + the loss algorithm, or it MAY omit the OC-Feature-Vector AVP. If it + selects a different algorithm, it MUST include the OC-Feature-Vector + AVP with an explicit indication of the selected algorithm. + + The reporting node SHOULD indicate support for other DOIC features + defined in extension documents that it supports and that apply to the + transaction. It does so using the OC-Feature-Vector AVP. + + Note: Not all DOIC features will apply to all Diameter + applications or deployment scenarios. The features included in + the OC-Feature-Vector AVP are based on local policy of the + reporting node. + +5.1.3. Agent Behavior + + Diameter Agents that support DOIC can ensure that all messages + relayed by the agent contain the OC-Supported-Features AVP. + + A Diameter Agent MAY take on reacting node behavior for Diameter + endpoints that do not support the DOIC solution. A Diameter Agent + detects that a Diameter endpoint does not support DOIC reacting node + behavior when there is no OC-Supported-Features AVP in a request + message. + + + + + +Korhonen, et al. Standards Track [Page 14] + +RFC 7683 DOIC October 2015 + + + For a Diameter Agent to be a reacting node for a non-supporting + Diameter endpoint, the Diameter Agent MUST include the OC-Supported- + Features AVP in request messages it relays that do not contain the + OC-Supported-Features AVP. + + A Diameter Agent MAY take on reporting node behavior for Diameter + endpoints that do not support the DOIC solution. The Diameter Agent + MUST have visibility to all traffic destined for the non-supporting + host in order to become the reporting node for the Diameter endpoint. + A Diameter Agent detects that a Diameter endpoint does not support + DOIC reporting node behavior when there is no OC-Supported-Features + AVP in an answer message for a transaction that contained the + OC-Supported-Features AVP in the request message. + + If a request already has the OC-Supported-Features AVP, a Diameter + Agent MAY modify it to reflect the features appropriate for the + transaction. Otherwise, the agent relays the OC-Supported-Features + AVP without change. + + Example: If the agent supports a superset of the features reported + by the reacting node, then the agent might choose, based on local + policy, to advertise that superset of features to the reporting + node. + + If the Diameter Agent changes the OC-Supported-Features AVP in a + request message, then it is likely it will also need to modify the + OC-Supported-Features AVP in the answer message for the transaction. + A Diameter Agent MAY modify the OC-Supported-Features AVP carried in + answer messages. + + When making changes to the OC-Supported-Features or OC-OLR AVPs, the + Diameter Agent needs to ensure consistency in its behavior with both + upstream and downstream DOIC nodes. + +5.2. Overload Report Processing + +5.2.1. Overload Control State + + Both reacting and reporting nodes maintain Overload Control State + (OCS) for active overload conditions. The following sections define + behavior associated with that OCS. + + The contents of the OCS in the reporting node and in the reacting + node represent logical constructs. The actual internal physical + structure of the state included in the OCS is an implementation + decision. + + + + + +Korhonen, et al. Standards Track [Page 15] + +RFC 7683 DOIC October 2015 + + +5.2.1.1. Overload Control State for Reacting Nodes + + A reacting node maintains the following OCS per supported Diameter + application: + + o a host-type OCS entry for each Destination-Host to which it sends + host-type requests and + + o a realm-type OCS entry for each Destination-Realm to which it + sends realm-type requests. + + A host-type OCS entry is identified by the pair of Application-ID and + the node's DiameterIdentity. + + A realm-type OCS entry is identified by the pair of Application-ID + and realm. + + The host-type and realm-type OCS entries include the following + information (the actual information stored is an implementation + decision): + + o Sequence number (as received in OC-OLR; see Section 7.3) + + o Time of expiry (derived from OC-Validity-Duration AVP received in + the OC-OLR AVP and time of reception of the message carrying + OC-OLR AVP) + + o Selected abatement algorithm (as received in the OC-Supported- + Features AVP) + + o Input data that is abatement algorithm specific (as received in + the OC-OLR AVP -- for example, OC-Reduction-Percentage for the + loss abatement algorithm) + +5.2.1.2. Overload Control State for Reporting Nodes + + A reporting node maintains OCS entries per supported Diameter + application, per supported (and eventually selected) abatement + algorithm, and per report type. + + An OCS entry is identified by the tuple of Application-ID, report + type, and abatement algorithm, and it includes the following + information (the actual information stored is an implementation + decision): + + o Sequence number + + o Validity duration + + + +Korhonen, et al. Standards Track [Page 16] + +RFC 7683 DOIC October 2015 + + + o Expiration time + + o Input data that is algorithm specific (for example, the reduction + percentage for the loss abatement algorithm) + +5.2.1.3. Reacting Node's Maintenance of Overload Control State + + When a reacting node receives an OC-OLR AVP, it MUST determine if it + is for an existing or new overload condition. + + Note: For the remainder of this section, the term "OLR" refers to + the combination of the contents of the received OC-OLR AVP and the + abatement algorithm indicated in the received OC-Supported- + Features AVP. + + When receiving an answer message with multiple OLRs of different + supported report types, a reacting node MUST process each received + OLR. + + The OLR is for an existing overload condition if a reacting node has + an OCS that matches the received OLR. + + For a host report, this means it matches the Application-ID and the + host's DiameterIdentity in an existing host OCS entry. + + For a realm report, this means it matches the Application-ID and the + realm in an existing realm OCS entry. + + If the OLR is for an existing overload condition, then a reacting + node MUST determine if the OLR is a retransmission or an update to + the existing OLR. + + If the sequence number for the received OLR is greater than the + sequence number stored in the matching OCS entry, then a reacting + node MUST update the matching OCS entry. + + If the sequence number for the received OLR is less than or equal to + the sequence number in the matching OCS entry, then a reacting node + MUST silently ignore the received OLR. The matching OCS MUST NOT be + updated in this case. + + If the reacting node determines that the sequence number has rolled + over, then the reacting node MUST update the matching OCS entry. + This can be determined by recognizing that the number has changed + from a value within 1% of the maximum value in the OC-Sequence-Number + AVP to a value within 1% of the minimum value in the OC-Sequence- + Number AVP. + + + + +Korhonen, et al. Standards Track [Page 17] + +RFC 7683 DOIC October 2015 + + + If the received OLR is for a new overload condition, then a reacting + node MUST generate a new OCS entry for the overload condition. + + For a host report, this means a reacting node creates an OCS entry + with the Application-ID in the received message and DiameterIdentity + of the Origin-Host in the received message. + + Note: This solution assumes that the Origin-Host AVP in the answer + message included by the reporting node is not changed along the + path to the reacting node. + + For a realm report, this means a reacting node creates an OCS entry + with the Application-ID in the received message and realm of the + Origin-Realm in the received message. + + If the received OLR contains a validity duration of zero ("0"), then + a reacting node MUST update the OCS entry as being expired. + + Note: It is not necessarily appropriate to delete the OCS entry, + as the recommended behavior is that the reacting node slowly + returns to full traffic when ending an overload abatement period. + + The reacting node does not delete an OCS when receiving an answer + message that does not contain an OC-OLR AVP (i.e., absence of OLR + means "no change"). + +5.2.1.4. Reporting Node's Maintenance of Overload Control State + + A reporting node SHOULD create a new OCS entry when entering an + overload condition. + + Note: If a reporting node knows through absence of the + OC-Supported-Features AVP in received messages that there are no + reacting nodes supporting DOIC, then the reporting node can choose + to not create OCS entries. + + When generating a new OCS entry, the sequence number SHOULD be set to + zero ("0"). + + When generating sequence numbers for new overload conditions, the new + sequence number MUST be greater than any sequence number in an active + (unexpired) overload report for the same application and report type + previously sent by the reporting node. This property MUST hold over + a reboot of the reporting node. + + + + + + + +Korhonen, et al. Standards Track [Page 18] + +RFC 7683 DOIC October 2015 + + + Note: One way of addressing this over a reboot of a reporting node + is to use a timestamp for the first overload condition that occurs + after the report and to start using sequences beginning with zero + for subsequent overload conditions. + + A reporting node MUST update an OCS entry when it needs to adjust the + validity duration of the overload condition at reacting nodes. + + Example: If a reporting node wishes to instruct reacting nodes to + continue overload abatement for a longer period of time than + originally communicated. This also applies if the reporting node + wishes to shorten the period of time that overload abatement is to + continue. + + A reporting node MUST update an OCS entry when it wishes to adjust + any parameters specific to the abatement algorithm, including, for + example, the reduction percentage used for the loss abatement + algorithm. + + Example: If a reporting node wishes to change the reduction + percentage either higher (if the overload condition has worsened) + or lower (if the overload condition has improved), then the + reporting node would update the appropriate OCS entry. + + A reporting node MUST increment the sequence number associated with + the OCS entry anytime the contents of the OCS entry are changed. + This will result in a new sequence number being sent to reacting + nodes, instructing them to process the OC-OLR AVP. + + A reporting node SHOULD update an OCS entry with a validity duration + of zero ("0") when the overload condition ends. + + Note: If a reporting node knows that the OCS entries in the + reacting nodes are near expiration, then the reporting node might + decide not to send an OLR with a validity duration of zero. + + A reporting node MUST keep an OCS entry with a validity duration of + zero ("0") for a period of time long enough to ensure that any + unexpired reacting node's OCS entry created as a result of the + overload condition in the reporting node is deleted. + +5.2.2. Reacting Node Behavior + + When a reacting node sends a request, it MUST determine if that + request matches an active OCS. + + + + + + +Korhonen, et al. Standards Track [Page 19] + +RFC 7683 DOIC October 2015 + + + If the request matches an active OCS, then the reacting node MUST use + the overload abatement algorithm indicated in the OCS to determine if + the request is to receive overload abatement treatment. + + For the loss abatement algorithm defined in this specification, see + Section 6 for the overload abatement algorithm logic applied. + + If the overload abatement algorithm selects the request for overload + abatement treatment, then the reacting node MUST apply overload + abatement treatment on the request. The abatement treatment applied + depends on the context of the request. + + If diversion abatement treatment is possible (i.e., a different path + for the request can be selected where the overloaded node is not part + of the different path), then the reacting node SHOULD apply diversion + abatement treatment to the request. The reacting node MUST apply + throttling abatement treatment to requests identified for abatement + treatment when diversion treatment is not possible or was not + applied. + + Note: This only addresses the case where there are two defined + abatement treatments, diversion and throttling. Any extension + that defines a new abatement treatment must also define its + interaction with existing treatments. + + If the overload abatement treatment results in throttling of the + request and if the reacting node is an agent, then the agent MUST + send an appropriate error as defined in Section 8. + + Diameter endpoints that throttle requests need to do so according to + the rules of the client application. Those rules will vary by + application and are beyond the scope of this document. + + In the case that the OCS entry indicated no traffic was to be sent to + the overloaded entity and the validity duration expires, then + overload abatement associated with the overload report MUST be ended + in a controlled fashion. + +5.2.3. Reporting Node Behavior + + If there is an active OCS entry, then a reporting node SHOULD include + the OC-OLR AVP in all answers to requests that contain the + OC-Supported-Features AVP and that match the active OCS entry. + + Note: A request matches 1) if the Application-ID in the request + matches the Application-ID in any active OCS entry and 2) if the + report type in the OCS entry matches a report type supported by + the reporting node as indicated in the OC-Supported-Features AVP. + + + +Korhonen, et al. Standards Track [Page 20] + +RFC 7683 DOIC October 2015 + + + The contents of the OC-OLR AVP depend on the selected algorithm. + + A reporting node MAY choose to not resend an overload report to a + reacting node if it can guarantee that this overload report is + already active in the reacting node. + + Note: In some cases (e.g., when there are one or more agents in + the path between reporting and reacting nodes, or when overload + reports are discarded by reacting nodes), a reporting node may not + be able to guarantee that the reacting node has received the + report. + + A reporting node MUST NOT send overload reports of a type that has + not been advertised as supported by the reacting node. + + Note: A reacting node implicitly advertises support for the host + and realm report types by including the OC-Supported-Features AVP + in the request. Support for other report types will be explicitly + indicated by new feature bits in the OC-Feature-Vector AVP. + + A reporting node SHOULD explicitly indicate the end of an overload + occurrence by sending a new OLR with OC-Validity-Duration set to a + value of zero ("0"). The reporting node SHOULD ensure that all + reacting nodes receive the updated overload report. + + A reporting node MAY rely on the OC-Validity-Duration AVP values for + the implicit cleanup of overload control state on the reacting node. + + Note: All OLRs sent have an expiration time calculated by adding + the validity duration contained in the OLR to the time the message + was sent. Transit time for the OLR can be safely ignored. The + reporting node can ensure that all reacting nodes have received + the OLR by continuing to send it in answer messages until the + expiration time for all OLRs sent for that overload condition have + expired. + + When a reporting node sends an OLR, it effectively delegates any + necessary throttling to downstream nodes. If the reporting node also + locally throttles the same set of messages, the overall number of + throttled requests may be higher than intended. Therefore, before + applying local message throttling, a reporting node needs to check if + these messages match existing OCS entries, indicating that these + messages have survived throttling applied by downstream nodes that + have received the related OLR. + + However, even if the set of messages match existing OCS entries, the + reporting node can still apply other abatement methods such as + diversion. The reporting node might also need to throttle requests + + + +Korhonen, et al. Standards Track [Page 21] + +RFC 7683 DOIC October 2015 + + + for reasons other than overload. For example, an agent or server + might have a configured rate limit for each client and might throttle + requests that exceed that limit, even if such requests had already + been candidates for throttling by downstream nodes. The reporting + node also has the option to send new OLRs requesting greater + reductions in traffic, reducing the need for local throttling. + + A reporting node SHOULD decrease requested overload abatement + treatment in a controlled fashion to avoid oscillations in traffic. + + Example: A reporting node might wait some period of time after + overload ends before terminating the OLR, or it might send a + series of OLRs indicating progressively less overload severity. + +5.3. Protocol Extensibility + + The DOIC solution can be extended. Types of potential extensions + include new traffic abatement algorithms, new report types, or other + new functionality. + + When defining a new extension that requires new normative behavior, + the specification must define a new feature for the OC-Feature-Vector + AVP. This feature bit is used to communicate support for the new + feature. + + The extension may define new AVPs for use in the DOIC Capability + Announcement and for use in DOIC overload reporting. These new AVPs + SHOULD be defined to be extensions to the OC-Supported-Features or + OC-OLR AVPs defined in this document. + + The Grouped AVP extension mechanisms defined in [RFC6733] apply. + This allows, for example, defining a new feature that is mandatory to + be understood even when piggybacked on an existing application. + + When defining new report type values, the corresponding specification + must define the semantics of the new report types and how they affect + the OC-OLR AVP handling. + + The OC-Supported-Feature and OC-OLR AVPs can be expanded with + optional sub-AVPs only if a legacy DOIC implementation can safely + ignore them without breaking backward compatibility for the given + OC-Report-Type AVP value. Any new sub-AVPs must not require that the + M-bit be set. + + Documents that introduce new report types must describe any + limitations on their use across non-supporting agents. + + + + + +Korhonen, et al. Standards Track [Page 22] + +RFC 7683 DOIC October 2015 + + + As with any Diameter specification, RFC 6733 requires all new AVPs to + be registered with IANA. See Section 9 for the required procedures. + New features (feature bits in the OC-Feature-Vector AVP) and report + types (in the OC-Report-Type AVP) MUST be registered with IANA. + +6. Loss Algorithm + + This section documents the Diameter overload loss abatement + algorithm. + +6.1. Overview + + The DOIC specification supports the ability for multiple overload + abatement algorithms to be specified. The abatement algorithm used + for any instance of overload is determined by the DOIC Capability + Announcement process documented in Section 5.1. + + The loss algorithm described in this section is the default algorithm + that must be supported by all Diameter nodes that support DOIC. + + The loss algorithm is designed to be a straightforward and stateless + overload abatement algorithm. It is used by reporting nodes to + request a percentage reduction in the amount of traffic sent. The + traffic impacted by the requested reduction depends on the type of + overload report. + + Reporting nodes request the stateless reduction of the number of + requests by an indicated percentage. This percentage reduction is in + comparison to the number of messages the node otherwise would send, + regardless of how many requests the node might have sent in the past. + + From a conceptual level, the logic at the reacting node could be + outlined as follows. + + 1. An overload report is received, and the associated OCS is either + saved or updated (if required) by the reacting node. + + 2. A new Diameter request is generated by the application running on + the reacting node. + + 3. The reacting node determines that an active overload report + applies to the request, as indicated by the corresponding OCS + entry. + + 4. The reacting node determines if overload abatement treatment + should be applied to the request. One approach that could be + taken for each request is to select a uniformly selected random + number between 1 and 100. If the random number is less than or + + + +Korhonen, et al. Standards Track [Page 23] + +RFC 7683 DOIC October 2015 + + + equal to the indicated reduction percentage, then the request is + given abatement treatment; otherwise, the request is given normal + routing treatment. + +6.2. Reporting Node Behavior + + The method a reporting node uses to determine the amount of traffic + reduction required to address an overload condition is an + implementation decision. + + When a reporting node that has selected the loss abatement algorithm + determines the need to request a reduction in traffic, it includes an + OC-OLR AVP in answer messages as described in Section 5.2.3. + + When sending the OC-OLR AVP, the reporting node MUST indicate a + percentage reduction in the OC-Reduction-Percentage AVP. + + The reporting node MAY change the reduction percentage in subsequent + overload reports. When doing so, the reporting node must conform to + overload report handling specified in Section 5.2.3. + +6.3. Reacting Node Behavior + + The method a reacting node uses to determine which request messages + are given abatement treatment is an implementation decision. + + When receiving an OC-OLR in an answer message where the algorithm + indicated in the OC-Supported-Features AVP is the loss algorithm, the + reacting node MUST apply abatement treatment to the requested + percentage of request messages sent. + + Note: The loss algorithm is a stateless algorithm. As a result, + the reacting node does not guarantee that there will be an + absolute reduction in traffic sent. Rather, it guarantees that + the requested percentage of new requests will be given abatement + treatment. + + If the reacting node comes out of the 100% traffic reduction + (meaning, it has received an OLR indicating that no traffic should be + sent, as a result of the overload report timing out), the reacting + node sending the traffic SHOULD be conservative and, for example, + first send "probe" messages to learn the overload condition of the + overloaded node before converging to any traffic amount/rate decided + by the sender. Similar concerns apply in all cases when the overload + report times out, unless the previous overload report stated 0% + reduction. + + + + + +Korhonen, et al. Standards Track [Page 24] + +RFC 7683 DOIC October 2015 + + + Note: The goal of this behavior is to reduce the probability of + overload condition thrashing where an immediate transition from + 100% reduction to 0% reduction results in the reporting node + moving quickly back into an overload condition. + +7. Attribute Value Pairs + + This section describes the encoding and semantics of the Diameter + Overload Indication Attribute Value Pairs (AVPs) defined in this + document. + + Refer to Section 4 of [RFC6733] for more information on AVPs and AVP + data types. + +7.1. OC-Supported-Features AVP + + The OC-Supported-Features AVP (AVP Code 621) is of type Grouped and + serves two purposes. First, it announces a node's support for the + DOIC solution in general. Second, it contains the description of the + supported DOIC features of the sending node. The OC-Supported- + Features AVP MUST be included in every Diameter request message a + DOIC supporting node sends. + + OC-Supported-Features ::= < AVP Header: 621 > + [ OC-Feature-Vector ] + * [ AVP ] + +7.2. OC-Feature-Vector AVP + + The OC-Feature-Vector AVP (AVP Code 622) is of type Unsigned64 and + contains a 64-bit flags field of announced capabilities of a DOIC + node. The value of zero (0) is reserved. + + The OC-Feature-Vector sub-AVP is used to announce the DOIC features + supported by the DOIC node, in the form of a flag-bits field in which + each bit announces one feature or capability supported by the node. + The absence of the OC-Feature-Vector AVP in request messages + indicates that only the default traffic abatement algorithm described + in this specification is supported. The absence of the OC-Feature- + Vector AVP in answer messages indicates that the default traffic + abatement algorithm described in this specification is selected + (while other traffic abatement algorithms may be supported), and no + features other than abatement algorithms are supported. + + + + + + + + +Korhonen, et al. Standards Track [Page 25] + +RFC 7683 DOIC October 2015 + + + The following capability is defined in this document: + + OLR_DEFAULT_ALGO (0x0000000000000001) + + When this flag is set by the a DOIC reacting node, it means that + the default traffic abatement (loss) algorithm is supported. When + this flag is set by a DOIC reporting node, it means that the loss + algorithm will be used for requested overload abatement. + +7.3. OC-OLR AVP + + The OC-OLR AVP (AVP Code 623) is of type Grouped and contains the + information necessary to convey an overload report on an overload + condition at the reporting node. The application the OC-OLR AVP + applies to is identified by the Application-ID found in the Diameter + message header. The host or realm the OC-OLR AVP concerns is + determined from the Origin-Host AVP and/or Origin-Realm AVP found in + the encapsulating Diameter command. The OC-OLR AVP is intended to be + sent only by a reporting node. + + OC-OLR ::= < AVP Header: 623 > + < OC-Sequence-Number > + < OC-Report-Type > + [ OC-Reduction-Percentage ] + [ OC-Validity-Duration ] + * [ AVP ] + +7.4. OC-Sequence-Number AVP + + The OC-Sequence-Number AVP (AVP Code 624) is of type Unsigned64. Its + usage in the context of overload control is described in Section 5.2. + + From the functionality point of view, the OC-Sequence-Number AVP is + used as a nonvolatile increasing counter for a sequence of overload + reports between two DOIC nodes for the same overload occurrence. + Sequence numbers are treated in a unidirectional manner, i.e., two + sequence numbers in each direction between two DOIC nodes are not + related or correlated. + +7.5. OC-Validity-Duration AVP + + The OC-Validity-Duration AVP (AVP Code 625) is of type Unsigned32 and + indicates in seconds the validity time of the overload report. The + number of seconds is measured after reception of the first OC-OLR AVP + with a given value of OC-Sequence-Number AVP. The default value for + the OC-Validity-Duration AVP is 30 seconds. When the OC-Validity- + Duration AVP is not present in the OC-OLR AVP, the default value + applies. The maximum value for the OC-Validity-Duration AVP is + + + +Korhonen, et al. Standards Track [Page 26] + +RFC 7683 DOIC October 2015 + + + 86,400 seconds (24 hours). If the value received in the OC-Validity- + Duration is greater than the maximum value, then the default value + applies. + +7.6. OC-Report-Type AVP + + The OC-Report-Type AVP (AVP Code 626) is of type Enumerated. The + value of the AVP describes what the overload report concerns. The + following values are initially defined: + + HOST_REPORT 0 + The overload report is for a host. Overload abatement treatment + applies to host-routed requests. + + REALM_REPORT 1 + The overload report is for a realm. Overload abatement treatment + applies to realm-routed requests. + + The values 2-4294967295 are unassigned. + +7.7. OC-Reduction-Percentage AVP + + The OC-Reduction-Percentage AVP (AVP Code 627) is of type Unsigned32 + and describes the percentage of the traffic that the sender is + requested to reduce, compared to what it otherwise would send. The + OC-Reduction-Percentage AVP applies to the default (loss) algorithm + specified in this specification. However, the AVP can be reused for + future abatement algorithms, if its semantics fit into the new + algorithm. + + The value of the Reduction-Percentage AVP is between zero (0) and one + hundred (100). Values greater than 100 are ignored. The value of + 100 means that all traffic is to be throttled, i.e., the reporting + node is under a severe load and ceases to process any new messages. + The value of 0 means that the reporting node is in a stable state and + has no need for the reacting node to apply any traffic abatement. + + + + + + + + + + + + + + + +Korhonen, et al. Standards Track [Page 27] + +RFC 7683 DOIC October 2015 + + +7.8. AVP Flag Rules + + +---------+ + |AVP flag | + |rules | + +----+----+ + AVP Section | |MUST| + Attribute Name Code Defined Value Type |MUST| NOT| + +--------------------------------------------------+----+----+ + |OC-Supported-Features 621 7.1 Grouped | | V | + +--------------------------------------------------+----+----+ + |OC-Feature-Vector 622 7.2 Unsigned64 | | V | + +--------------------------------------------------+----+----+ + |OC-OLR 623 7.3 Grouped | | V | + +--------------------------------------------------+----+----+ + |OC-Sequence-Number 624 7.4 Unsigned64 | | V | + +--------------------------------------------------+----+----+ + |OC-Validity-Duration 625 7.5 Unsigned32 | | V | + +--------------------------------------------------+----+----+ + |OC-Report-Type 626 7.6 Enumerated | | V | + +--------------------------------------------------+----+----+ + |OC-Reduction | | | + | -Percentage 627 7.7 Unsigned32 | | V | + +--------------------------------------------------+----+----+ + + As described in the Diameter base protocol [RFC6733], the M-bit usage + for a given AVP in a given command may be defined by the application. + +8. Error Response Codes + + When a DOIC node rejects a Diameter request due to overload, the DOIC + node MUST select an appropriate error response code. This + determination is made based on the probability of the request + succeeding if retried on a different path. + + Note: This only applies for DOIC nodes that are not the originator + of the request. + + A reporting node rejecting a Diameter request due to an overload + condition SHOULD send a DIAMETER_TOO_BUSY error response, if it can + assume that the same request may succeed on a different path. + + If a reporting node knows or assumes that the same request will not + succeed on a different path, the DIAMETER_UNABLE_TO_COMPLY error + response SHOULD be used. Retrying would consume valuable resources + during an occurrence of overload. + + + + + +Korhonen, et al. Standards Track [Page 28] + +RFC 7683 DOIC October 2015 + + + For instance, if the request arrived at the reporting node without + a Destination-Host AVP, then the reporting node might determine + that there is an alternative Diameter node that could successfully + process the request and that retrying the transaction would not + negatively impact the reporting node. DIAMETER_TOO_BUSY would be + sent in this case. + + If the request arrived at the reporting node with a Destination- + Host AVP populated with its own Diameter identity, then the + reporting node can assume that retrying the request would result + in it coming to the same reporting node. + DIAMETER_UNABLE_TO_COMPLY would be sent in this case. + + A second example is when an agent that supports the DOIC solution + is performing the role of a reacting node for a non-supporting + client. Requests that are rejected as a result of DOIC throttling + by the agent in this scenario would generally be rejected with a + DIAMETER_UNABLE_TO_COMPLY response code. + +9. IANA Considerations + +9.1. AVP Codes + + New AVPs defined by this specification are listed in Section 7. All + AVP codes are allocated from the "AVP Codes" sub-registry under the + "Authentication, Authorization, and Accounting (AAA) Parameters" + registry. + +9.2. New Registries + + Two new registries have been created in the "AVP Specific Values" + sub-registry under the "Authentication, Authorization, and Accounting + (AAA) Parameters" registry. + + A new "OC-Feature-Vector AVP Values (code 622)" registry has been + created. This registry contains the following: + + Feature Vector Value Name + + Feature Vector Value + + Specification defining the new value + + See Section 7.2 for the initial Feature Vector Value in the registry. + This specification defines the value. New values can be added to the + registry using the Specification Required policy [RFC5226]. + + + + + +Korhonen, et al. Standards Track [Page 29] + +RFC 7683 DOIC October 2015 + + + A new "OC-Report-Type AVP Values (code 626)" registry has been + created. This registry contains the following: + + Report Type Value Name + + Report Type Value + + Specification defining the new value + + See Section 7.6 for the initial assignment in the registry. New + types can be added using the Specification Required policy [RFC5226]. + +10. Security Considerations + + DOIC gives Diameter nodes the ability to request that downstream + nodes send fewer Diameter requests. Nodes do this by exchanging + overload reports that directly effect this reduction. This exchange + is potentially subject to multiple methods of attack and has the + potential to be used as a denial-of-service (DoS) attack vector. For + instance, a series of injected realm OLRs with a requested reduction + percentage of 100% could be used to completely eliminate any traffic + from being sent to that realm. + + Overload reports may contain information about the topology and + current status of a Diameter network. This information is + potentially sensitive. Network operators may wish to control + disclosure of overload reports to unauthorized parties to avoid their + use for competitive intelligence or to target attacks. + + Diameter does not include features to provide end-to-end + authentication, integrity protection, or confidentiality. This may + cause complications when sending overload reports between non- + adjacent nodes. + +10.1. Potential Threat Modes + + The Diameter protocol involves transactions in the form of requests + and answers exchanged between clients and servers. These clients and + servers may be peers, that is, they may share a direct transport + (e.g., TCP or SCTP) connection, or the messages may traverse one or + more intermediaries, known as Diameter Agents. Diameter nodes use + TLS, DTLS, or IPsec to authenticate peers and to provide + confidentiality and integrity protection of traffic between peers. + Nodes can make authorization decisions based on the peer identities + authenticated at the transport layer. + + + + + + +Korhonen, et al. Standards Track [Page 30] + +RFC 7683 DOIC October 2015 + + + When agents are involved, this presents an effectively transitive + trust model. That is, a Diameter client or server can authorize an + agent for certain actions, but it must trust that agent to make + appropriate authorization decisions about its peers, and so on. + Since confidentiality and integrity protection occur at the transport + layer, agents can read, and perhaps modify, any part of a Diameter + message, including an overload report. + + There are several ways an attacker might attempt to exploit the + overload control mechanism. An unauthorized third party might inject + an overload report into the network. If this third party is upstream + of an agent, and that agent fails to apply proper authorization + policies, downstream nodes may mistakenly trust the report. This + attack is at least partially mitigated by the assumption that nodes + include overload reports in Diameter answers but not in requests. + This requires an attacker to have knowledge of the original request + in order to construct an answer. Such an answer would also need to + arrive at a Diameter node via a protected transport connection. + Therefore, implementations MUST validate that an answer containing an + overload report is a properly constructed response to a pending + request prior to acting on the overload report, and that the answer + was received via an appropriate transport connection. + + A similar attack involves a compromised but otherwise authorized node + that sends an inappropriate overload report. For example, a server + for the realm "example.com" might send an overload report indicating + that a competitor's realm "example.net" is overloaded. If other + nodes act on the report, they may falsely believe that "example.net" + is overloaded, effectively reducing that realm's capacity. + Therefore, it's critical that nodes validate that an overload report + received from a peer actually falls within that peer's responsibility + before acting on the report or forwarding the report to other peers. + For example, an overload report from a peer that applies to a realm + not handled by that peer is suspect. This may require out-of-band, + non-Diameter agreements and/or mechanisms. + + This attack is partially mitigated by the fact that the + application, as well as host and realm, for a given OLR is + determined implicitly by respective AVPs in the enclosing answer. + If a reporting node modifies any of those AVPs, the enclosing + transaction will also be affected. + +10.2. Denial-of-Service Attacks + + Diameter overload reports, especially realm reports, can cause a node + to cease sending some or all Diameter requests for an extended + period. This makes them a tempting vector for DoS attacks. + Furthermore, since Diameter is almost always used in support of other + + + +Korhonen, et al. Standards Track [Page 31] + +RFC 7683 DOIC October 2015 + + + protocols, a DoS attack on Diameter is likely to impact those + protocols as well. In the worst case, where the Diameter application + is being used for access control into an IP network, a coordinated + DoS attack could result in the blockage of all traffic into that + network. Therefore, Diameter nodes MUST NOT honor or forward OLRs + received from peers that are not trusted to send them. + + An attacker might use the information in an OLR to assist in DoS + attacks. For example, an attacker could use information about + current overload conditions to time an attack for maximum effect, or + use subsequent overload reports as a feedback mechanism to learn the + results of a previous or ongoing attack. Operators need the ability + to ensure that OLRs are not leaked to untrusted parties. + +10.3. Noncompliant Nodes + + In the absence of an overload control mechanism, Diameter nodes need + to implement strategies to protect themselves from floods of + requests, and to make sure that a disproportionate load from one + source does not prevent other sources from receiving service. For + example, a Diameter server might throttle a certain percentage of + requests from sources that exceed certain limits. Overload control + can be thought of as an optimization for such strategies, where + downstream nodes never send the excess requests in the first place. + However, the presence of an overload control mechanism does not + remove the need for these other protection strategies. + + When a Diameter node sends an overload report, it cannot assume that + all nodes will comply, even if they indicate support for DOIC. A + noncompliant node might continue to send requests with no reduction + in load. Such noncompliance could be done accidentally or + maliciously to gain an unfair advantage over compliant nodes. + Requirement 28 in [RFC7068] indicates that the overload control + solution cannot assume that all Diameter nodes in a network are + trusted. It also requires that malicious nodes not be allowed to + take advantage of the overload control mechanism to get more than + their fair share of service. + +10.4. End-to-End Security Issues + + The lack of end-to-end integrity features makes it difficult to + establish trust in overload reports received from non-adjacent nodes. + Any agents in the message path may insert or modify overload reports. + Nodes must trust that their adjacent peers perform proper checks on + overload reports from their peers, and so on, creating a transitive- + trust requirement extending for potentially long chains of nodes. + Network operators must determine if this transitive trust requirement + is acceptable for their deployments. Nodes supporting Diameter + + + +Korhonen, et al. Standards Track [Page 32] + +RFC 7683 DOIC October 2015 + + + overload control MUST give operators the ability to select which + peers are trusted to deliver overload reports and whether they are + trusted to forward overload reports from non-adjacent nodes. DOIC + nodes MUST strip DOIC AVPs from messages received from peers that are + not trusted for DOIC purposes. + + The lack of end-to-end confidentiality protection means that any + Diameter Agent in the path of an overload report can view the + contents of that report. In addition to the requirement to select + which peers are trusted to send overload reports, operators MUST be + able to select which peers are authorized to receive reports. A node + MUST NOT send an overload report to a peer not authorized to receive + it. Furthermore, an agent MUST remove any overload reports that + might have been inserted by other nodes before forwarding a Diameter + message to a peer that is not authorized to receive overload reports. + + A DOIC node cannot always automatically detect that a peer also + supports DOIC. For example, a node might have a peer that is a + non-supporting agent. If nodes on the other side of that agent + send OC-Supported-Features AVPs, the agent is likely to forward + them as unknown AVPs. Messages received across the non-supporting + agent may be indistinguishable from messages received across a + DOIC supporting agent, giving the false impression that the non- + supporting agent actually supports DOIC. This complicates the + transitive-trust nature of DOIC. Operators need to be careful to + avoid situations where a non-supporting agent is mistakenly + trusted to enforce DOIC-related authorization policies. + + It is expected that work on end-to-end Diameter security might make + it easier to establish trust in non-adjacent nodes for overload + control purposes. Readers should be reminded, however, that the + overload control mechanism allows Diameter Agents to modify AVPs in, + or insert additional AVPs into, existing messages that are originated + by other nodes. If end-to-end security is enabled, there is a risk + that such modification could violate integrity protection. The + details of using any future Diameter end-to-end security mechanism + with overload control will require careful consideration, and are + beyond the scope of this document. + + + + + + + + + + + + + +Korhonen, et al. Standards Track [Page 33] + +RFC 7683 DOIC October 2015 + + +11. References + +11.1. Normative References + + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, + DOI 10.17487/RFC2119, March 1997, + <http://www.rfc-editor.org/info/rfc2119>. + + [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an + IANA Considerations Section in RFCs", BCP 26, RFC 5226, + DOI 10.17487/RFC5226, May 2008, + <http://www.rfc-editor.org/info/rfc5226>. + + [RFC6733] Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn, + Ed., "Diameter Base Protocol", RFC 6733, + DOI 10.17487/RFC6733, October 2012, + <http://www.rfc-editor.org/info/rfc6733>. + +11.2. Informative References + + [Cx] 3GPP, "Cx and Dx interfaces based on the Diameter + protocol; Protocol details", 3GPP TS 29.229 12.7.0, + September 2015. + + [PCC] 3GPP, "Policy and charging control architecture", 3GPP + TS 23.203 12.10.0, September 2015. + + [RFC4006] Hakala, H., Mattila, L., Koskinen, J-P., Stura, M., and J. + Loughney, "Diameter Credit-Control Application", RFC 4006, + DOI 10.17487/RFC4006, August 2005, + <http://www.rfc-editor.org/info/rfc4006>. + + [RFC7068] McMurry, E. and B. Campbell, "Diameter Overload Control + Requirements", RFC 7068, DOI 10.17487/RFC7068, November + 2013, <http://www.rfc-editor.org/info/rfc7068>. + + [S13] 3GPP, "Evolved Packet System (EPS); Mobility Management + Entity (MME) and Serving GPRS Support Node (SGSN) related + interfaces based on Diameter protocol", 3GPP TS 29.272 + 12.8.0, September 2015. + + + + + + + + + + +Korhonen, et al. Standards Track [Page 34] + +RFC 7683 DOIC October 2015 + + +Appendix A. Issues Left for Future Specifications + + The base solution for overload control does not cover all possible + use cases. A number of solution aspects were intentionally left for + future specification and protocol work. The following subsections + define some of the potential extensions to the DOIC solution. + +A.1. Additional Traffic Abatement Algorithms + + This specification describes only means for a simple loss-based + algorithm. Future algorithms can be added using the designed + solution extension mechanism. The new algorithms need to be + registered with IANA. See Sections 7.2 and 9 for the required IANA + steps. + +A.2. Agent Overload + + This specification focuses on Diameter endpoint (server or client) + overload. A separate extension will be required to outline the + handling of the case of agent overload. + +A.3. New Error Diagnostic AVP + + This specification indicates the use of existing error messages when + nodes reject requests due to overload. There is an expectation that + additional error codes or AVPs will be defined in a separate + specification to indicate that overload was the reason for the + rejection of the message. + +Appendix B. Deployment Considerations + + Non-supporting Agents + + Due to the way that realm-routed requests are handled in Diameter + networks with the server selection for the request done by an + agent, network operators should enable DOIC at agents that perform + server selection first. + + Topology-Hiding Interactions + + There exist proxies that implement what is referred to as Topology + Hiding. This can include cases where the agent modifies the + Origin-Host in answer messages. The behavior of the DOIC solution + is not well understood when this happens. As such, the DOIC + solution does not address this scenario. + + + + + + +Korhonen, et al. Standards Track [Page 35] + +RFC 7683 DOIC October 2015 + + + Inter-Realm/Administrative Domain Considerations + + There are likely to be special considerations for handling DOIC + signaling across administrative boundaries. This includes + considerations for whether or not information included in the DOIC + signaling should be sent across those boundaries. In addition, + consideration should be taken as to whether or not a reacting node + in one realm can be trusted to implement the requested overload + abatement handling for overload reports received from a separately + administered realm. + +Appendix C. Considerations for Applications Integrating the DOIC + Solution + + This section outlines considerations to be taken into account when + integrating the DOIC solution into Diameter applications. + +C.1. Application Classification + + The following is a classification of Diameter applications and + request types. This discussion is meant to document factors that + play into decisions made by the Diameter entity responsible for + handling overload reports. + + Section 8.1 of [RFC6733] defines two state machines that imply two + types of applications, session-less and session-based applications. + The primary difference between these types of applications is the + lifetime of Session-Ids. + + For session-based applications, the Session-Id is used to tie + multiple requests into a single session. + + The Credit-Control application defined in [RFC4006] is an example of + a Diameter session-based application. + + In session-less applications, the lifetime of the Session-Id is a + single Diameter transaction, i.e., the session is implicitly + terminated after a single Diameter transaction and a new Session-Id + is generated for each Diameter request. + + + + + + + + + + + + +Korhonen, et al. Standards Track [Page 36] + +RFC 7683 DOIC October 2015 + + + For the purposes of this discussion, session-less applications are + further divided into two types of applications: + + Stateless Applications: + + Requests within a stateless application have no relationship to + each other. The 3GPP-defined S13 application is an example of a + stateless application [S13], where only a Diameter command is + defined between a client and a server and no state is maintained + between two consecutive transactions. + + Pseudo-Session Applications: + + Applications that do not rely on the Session-Id AVP for + correlation of application messages related to the same session + but use other session-related information in the Diameter requests + for this purpose. The 3GPP-defined Cx application [Cx] is an + example of a pseudo-session application. + + The handling of overload reports must take the type of application + into consideration, as discussed in Appendix C.2. + +C.2. Implications of Application Type Overload + + This section discusses considerations for mitigating overload + reported by a Diameter entity. This discussion focuses on the type + of application. Appendix C.3 discusses considerations for handling + various request types when the target server is known to be in an + overloaded state. + + These discussions assume that the strategy for mitigating the + reported overload is to reduce the overall workload sent to the + overloaded entity. The concept of applying overload treatment to + requests targeted for an overloaded Diameter entity is inherent to + this discussion. The method used to reduce offered load is not + specified here, but it could include routing requests to another + Diameter entity known to be able to handle them, or it could mean + rejecting certain requests. For a Diameter Agent, rejecting requests + will usually mean generating appropriate Diameter error responses. + For a Diameter client, rejecting requests will depend upon the + application. For example, it could mean giving an indication to the + entity requesting the Diameter service that the network is busy and + to try again later. + + + + + + + + +Korhonen, et al. Standards Track [Page 37] + +RFC 7683 DOIC October 2015 + + + Stateless Applications: + + By definition, there is no relationship between individual + requests in a stateless application. As a result, when a request + is sent or relayed to an overloaded Diameter entity -- either a + Diameter Server or a Diameter Agent -- the sending or relaying + entity can choose to apply the overload treatment to any request + targeted for the overloaded entity. + + Pseudo-session Applications: + + For pseudo-session applications, there is an implied ordering of + requests. As a result, decisions about which requests towards an + overloaded entity to reject could take the command code of the + request into consideration. This generally means that + transactions later in the sequence of transactions should be given + more favorable treatment than messages earlier in the sequence. + This is because more work has already been done by the Diameter + network for those transactions that occur later in the sequence. + Rejecting them could result in increasing the load on the network + as the transactions earlier in the sequence might also need to be + repeated. + + Session-Based Applications: + + Overload handling for session-based applications must take into + consideration the work load associated with setting up and + maintaining a session. As such, the entity sending requests + towards an overloaded Diameter entity for a session-based + application might tend to reject new session requests prior to + rejecting intra-session requests. In addition, session-ending + requests might be given a lower probability of being rejected, as + rejecting session-ending requests could result in session status + being out of sync between the Diameter clients and servers. + Application designers that would decide to reject mid-session + requests will need to consider whether the rejection invalidates + the session and any resulting session cleanup procedures. + +C.3. Request Transaction Classification + + Independent Request: + + An independent request is not correlated to any other requests, + and, as such, the lifetime of the Session-Id is constrained to an + individual transaction. + + + + + + +Korhonen, et al. Standards Track [Page 38] + +RFC 7683 DOIC October 2015 + + + Session-Initiating Request: + + A session-initiating request is the initial message that + establishes a Diameter session. The ACR message defined in + [RFC6733] is an example of a session-initiating request. + + Correlated Session-Initiating Request: + + There are cases when multiple session-initiated requests must be + correlated and managed by the same Diameter server. It is notably + the case in the 3GPP Policy and Charging Control (PCC) + architecture [PCC], where multiple apparently independent Diameter + application sessions are actually correlated and must be handled + by the same Diameter server. + + Intra-session Request: + + An intra-session request is a request that uses the same Session- + Id as the one used in a previous request. An intra-session + request generally needs to be delivered to the server that handled + the session-creating request for the session. The STR message + defined in [RFC6733] is an example of an intra-session request. + + Pseudo-session Requests: + + Pseudo-session requests are independent requests and do not use + the same Session-Id but are correlated by other session-related + information contained in the request. There exist Diameter + applications that define an expected ordering of transactions. + This sequencing of independent transactions results in a pseudo- + session. The AIR, MAR, and SAR requests in the 3GPP-defined Cx + [Cx] application are examples of pseudo-session requests. + +C.4. Request Type Overload Implications + + The request classes identified in Appendix C.3 have implications on + decisions about which requests should be throttled first. The + following list of request treatments regarding throttling is provided + as guidelines for application designers when implementing the + Diameter overload control mechanism described in this document. The + exact behavior regarding throttling is a matter of local policy, + unless specifically defined for the application. + + Independent Requests: + + Independent requests can generally be given equal treatment when + making throttling decisions, unless otherwise indicated by + application requirements or local policy. + + + +Korhonen, et al. Standards Track [Page 39] + +RFC 7683 DOIC October 2015 + + + Session-Initiating Requests: + + Session-initiating requests often represent more work than + independent or intra-session requests. Moreover, session- + initiating requests are typically followed by other session- + related requests. Since the main objective of overload control is + to reduce the total number of requests sent to the overloaded + entity, throttling decisions might favor allowing intra-session + requests over session-initiating requests. In the absence of + local policies or application-specific requirements to the + contrary, individual session-initiating requests can be given + equal treatment when making throttling decisions. + + Correlated Session-Initiating Requests: + + A request that results in a new binding; where the binding is used + for routing of subsequent session-initiating requests to the same + server, it represents more work load than other requests. As + such, these requests might be throttled more frequently than other + request types. + + Pseudo-session Requests: + + Throttling decisions for pseudo-session requests can take into + consideration where individual requests fit into the overall + sequence of requests within the pseudo-session. Requests that are + earlier in the sequence might be throttled more aggressively than + requests that occur later in the sequence. + + Intra-session Requests: + + There are two types of intra-sessions requests, requests that + terminate a session and the remainder of intra-session requests. + Implementers and operators may choose to throttle session- + terminating requests less aggressively in order to gracefully + terminate sessions, allow cleanup of the related resources (e.g., + session state), and avoid the need for additional intra-session + requests. Favoring session termination requests may reduce the + session management impact on the overloaded entity. The default + handling of other intra-session requests might be to treat them + equally when making throttling decisions. There might also be + application-level considerations whether some request types are + favored over others. + + + + + + + + +Korhonen, et al. Standards Track [Page 40] + +RFC 7683 DOIC October 2015 + + +Contributors + + The following people contributed substantial ideas, feedback, and + discussion to this document: + + o Eric McMurry + + o Hannes Tschofenig + + o Ulrich Wiehe + + o Jean-Jacques Trottin + + o Maria Cruz Bartolome + + o Martin Dolly + + o Nirav Salot + + o Susan Shishufeng + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Korhonen, et al. Standards Track [Page 41] + +RFC 7683 DOIC October 2015 + + +Authors' Addresses + + Jouni Korhonen (editor) + Broadcom Corporation + 3151 Zanker Road + San Jose, CA 95134 + United States + + Email: [email protected] + + + Steve Donovan (editor) + Oracle + 7460 Warren Parkway + Frisco, Texas 75034 + United States + + Email: [email protected] + + + Ben Campbell + Oracle + 7460 Warren Parkway + Frisco, Texas 75034 + United States + + Email: [email protected] + + + Lionel Morand + Orange Labs + 38/40 rue du General Leclerc + Issy-Les-Moulineaux Cedex 9 92794 + France + + Phone: +33145296257 + Email: [email protected] + + + + + + + + + + + + + + +Korhonen, et al. Standards Track [Page 42] + |