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authorAnders Svensson <[email protected]>2012-10-05 03:09:07 +0200
committerAnders Svensson <[email protected]>2012-11-05 11:53:44 +0100
commit2ba65b0d81b6a047bed3babf5371e500c1a72541 (patch)
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parentf4db5c422a17735f4e571276332ce8582b563aac (diff)
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Document sequence masks
Allow 32-bit Hop-by-Hop and End-to-End identifiers to be modified by replacing the topmost bits with a constant value. This allow services on different nodes to generate globally unique identifiers by having each node mask in its own constant.
Diffstat (limited to 'lib/diameter/doc')
-rw-r--r--lib/diameter/doc/src/diameter.xml29
1 files changed, 29 insertions, 0 deletions
diff --git a/lib/diameter/doc/src/diameter.xml b/lib/diameter/doc/src/diameter.xml
index b8652a7482..161fd94d5a 100644
--- a/lib/diameter/doc/src/diameter.xml
+++ b/lib/diameter/doc/src/diameter.xml
@@ -699,6 +699,35 @@ the application's <seealso marker="diameter_dict">dictionary</seealso>
file.</p>
</item>
+<tag><c>{sequence, {H,N} | <seealso
+ marker="diameter#evaluable">diameter:evaluable()</seealso>}</c></tag>
+<item>
+<p>
+Specifies a constant value <c>H</c> for the topmost <c>32-N</c> bits of
+of 32-bit End-to-End and Hop-by-Hop identifiers generated
+by the service, either explicity or as a return value of a function
+to be evaluated at <seealso
+marker="diameter#start_service">diameter:start_service/2</seealso>.
+In particular, an identifier <c>Id</c> is mapped to a new identifier
+as follows.</p>
+<code>
+(H bsl N) bor (Id band ((1 bsl N) - 1))
+</code>
+<p>
+Note that RFC 3588 requires that End-to-End identifiers remain unique
+for a period of at least 4 minutes and that this and the call rate
+places a lower bound on the appropriate values of <c>N</c>:
+at a rate of <c>R</c> requests per second an <c>N</c>-bit counter
+traverses all of its values in <c>(1 bsl N) div (R*60)</c> minutes so
+the bound is <c>4*R*60 =&lt; 1 bsl N</c>.</p>
+
+<p><c>N</c> must lie in the range <c>0..32</c> and <c>H</c> must be a
+non-negative integer less than <c>1 bsl (32-N)</c>.</p>
+
+<p>
+Defaults to <c>{0,32}</c>.</p>
+</item>
+
</taglist>
<marker id="transport_opt"/>