[rohc] rfc5225 RoHCv2 ipv4_outer_irregular format question
Klaus Warnke <klaus.warnke@acticom.de> Fri, 13 April 2012 14:57 UTC
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Date: Fri, 13 Apr 2012 16:57:14 +0200
From: Klaus Warnke <klaus.warnke@acticom.de>
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Subject: [rohc] rfc5225 RoHCv2 ipv4_outer_irregular format question
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Hello In the encoding method ipv4() in the format ipv4_outer_irregular{}: COMPRESSED ipv4_outer_irregular { ENFORCE(is_innermost == 0); ip_id =:= ip_id_enc_irreg(ip_id_behavior_outer.UVALUE) [ 0, 16 ]; tos_tc =:= static_or_irreg(outer_ip_flag, 8) [ 0, 8 ]; ttl_hopl =:= static_or_irreg(outer_ip_flag, 8) [ 0, 8 ]; } I could not determine how the value of the IP-ID in case of ip_id_behavior_outer is either IP_ID_BEHAVIOR_SEQUENTIAL or IP_ID_BEHAVIOR_SEQUENTIAL_SWAPPED is computed. The encoding method ip_id_enc_irreg() is used to handle the IP-ID here. But for the IP-ID behavior cases stated above I can not figure out, how it is computed. Did I oversee something? Maybe the line ip_id =:= inferred_sequential_ip_id [ 0 ]; is absent here? But it could not be, because the English text definition talks about ip_id_behavior_innermost. ip_id_enc_irreg(behavior) { UNCOMPRESSED { ip_id [ 16 ]; } COMPRESSED ip_id_seq { ENFORCE(behavior == IP_ID_BEHAVIOR_SEQUENTIAL); +++ ip_id =:= inferred_sequential_ip_id [ 0 ]; } COMPRESSED ip_id_seq_swapped { ENFORCE(behavior == IP_ID_BEHAVIOR_SEQUENTIAL_SWAPPED); +++ ip_id =:= inferred_sequential_ip_id [ 0 ]; } COMPRESSED ip_id_rand { ENFORCE(behavior == IP_ID_BEHAVIOR_RANDOM); ip_id =:= irregular(16) [ 16 ]; } COMPRESSED ip_id_zero { ENFORCE(behavior == IP_ID_BEHAVIOR_ZERO); ip_id =:= uncompressed_value(16, 0) [ 0 ]; } } If not, could please someone explain, how the IP-ID is computed for the outer headers? Or in other words: If I receive an ipv4_outer_irregular{} format, how I get the IP-ID, if its behavior is sequential or sequential swapped, i.e. no IP-ID bits are received within the irregular chain. Thanks and regards, Klaus -- Klaus Warnke klaus.warnke@acticom.de http://www.acticom.de Tel +49-30-4849.6891 acticom GmbH Schwedter Str. 9b, 10119 Berlin, Germany Managing Directors: Olaf Kehrer, Gerrit Schulte Commercial Register: Berlin-Charlottenburg HRB 73245 VAT-ID DE205131766
- [rohc] rfc5225 RoHCv2 ipv4_outer_irregular format… Klaus Warnke