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-rw-r--r--lib/asn1/doc/src/asn1_ug.xml57
1 files changed, 0 insertions, 57 deletions
diff --git a/lib/asn1/doc/src/asn1_ug.xml b/lib/asn1/doc/src/asn1_ug.xml
index ce8da39e6d..2522333d77 100644
--- a/lib/asn1/doc/src/asn1_ug.xml
+++ b/lib/asn1/doc/src/asn1_ug.xml
@@ -1415,62 +1415,5 @@ T2 ::= General{BIT STRING}
encode/decode functions will only be generated for T1 and T2.
</p>
</section>
-
- <section>
- <title>Encoding Rules</title>
- <p>When the first recommendation on ASN.1 was released 1988 it was
- accompanied with the Basic Encoding Rules, BER, as the only
- alternative for encoding.
- BER is a somewhat verbose protocol. It adopts a so-called TLV (type,
- length, value) approach to encoding in which every element of the
- encoding carries some type information, some length information and
- then the value of that element. Where the element is itself
- structured, then the Value part of the element is itself a series of
- embedded TLV components, to whatever depth is necessary. In summary,
- BER is not a compact encoding but is relatively fast and easy to
- produce.</p>
- <p>The DER (Distinguished Encoding Rule) encoding format was included in
- the standard in 1994. It is a specialized form of BER, which gives
- the encoder the option to encode some entities differently. For
- instance, is the value for TRUE any octet with any bit set to one. But,
- DER does not leave any such choices. The value for TRUE in the DER
- case is encoded as the octet <c>11111111</c>. So, the same value
- encoded by two different DER encoders must result in the same bit
- stream.</p>
- <p>A more compact encoding is achieved with the Packed Encoding
- Rules PER which was introduced together with the revised
- recommendation in 1994. PER takes a rather different approach from
- that taken by BER. The first difference is that the tag part in
- the TLV is omitted from the encodings, and any tags in the
- notation are not encoded. The potential ambiguities are resolved
- as follows:</p>
- <list type="bulleted">
- <item>
- <p>A CHOICE is encoded by first encoding a choice index which
- identifies the chosen
- alternative by its position in the notation.</p>
- </item>
- <item>
- <p>The elements of a SEQUENCE are transmitted in textual
- order. OPTIONAL or DEFAULT elements are preceded by a bit map
- to identify which elements are present. After sorting the
- elements of a SET in the "canonical tag order" as defined in
- X.680 8.6 they are treated as a SEQUENCE regarding OPTIONAL
- and DEFAULT elements. A SET is transferred in the sorted
- order.</p>
- </item>
- </list>
- <p>A second difference is that PER takes full account of the sub-typing
- information in that the encoded bytes are affected by the constraints.
- The BER encoded bytes are unaffected by the constraints.
- PER uses the sub-typing information to for example omit length fields
- whenever possible. </p>
- <p>The run-time functions, sometimes take the constraints into account
- both for BER and PER. For instance are SIZE constrained strings checked.</p>
- <p>There are two variants of PER, <em>aligned</em> and <em>unaligned</em>.
- In summary, PER results in compact encodings which require much more
- computation to produce than BER.
- </p>
- </section>
</chapter>