Legacy Issue Number: 7611
Source: Nokia ( Kimmo Raatikainen)
Usage of sequence numbers in UDP Tunneling Protocol messages in section 7.4 needs refinements.
We have found the following two problems:
1) If the first sequence number is arbitrary, then the receiver must examine the playload before it can detect whether or not the beginning of the message sequence is received.
2) If UTP messages containing only Acknowledge chunck are acknowledged, then we will have an infinite loop of ackning acks.
1) Start sequence numbers always from 0x0001.
2) Reserve sequence number 0x0000 for UTP messages that are not to be acknowledged (messages that only contain Acknowledge and/or Pause chunk).
Add a new subsection 'Sequence Numberging' after the subsection 7.4.1 'UDP Tunneling Protocol':
Each communication session must start sequence numbering from 0x0001. In other words the UTP message containing the InitialAccessRequest chunk (or its first fragment) and the associated reply containing the InitialAccessReply chunk (or its first fragment) MUST have UTP Sequence Number 0x0001.
The sequence number counting follows the usual modulo arithmetic with the exception that the sequence number 0x0001 follows the sequence number 0xFFFF.
The UTP Sequence Number 0x0000 is reserved for UTP messages that only contain the Acknowledge chunk and/or the Pause chunk. These messages MUST NOT be acknowledged.
Add the following note at the end of subsections 7.4.3 'InitialAccessRequest' and 7.4.4 'InitialAccessReply':
Note: UTP message containing this chunk (or its first fragment) MUST have sequence number 0x0001.
Add the following two notes at the end of subsection 7.4.5 'Pause':
Note 1: If the UTP message contains only the Pause chunk (with or without the Acknowledge chunk), then the UTP Sequence Number MUST be 0x0000. The receiver SHOULD NOT acknowledge such a message.
Note 2: After sending the Pause chunk, the sender SHOULD reply to each arriving message by a UTP message containing the Pause chunk. The UTP message MAY also contain ACknowledge and/or GTPData chunks.
Add the following note at the end of subsection 7.4.7 'Acknowledge':
Note: If the UTP message contains only the Acknowledge chunk (with or without the Pause chunk), then the UTP Sequence Number MUST be 0x0000. The receiver SHOULD NOT acknowledge such a message.
Reported: WATM 1.0 — Mon, 2 Aug 2004 04:00 GMT
Disposition: Resolved — WATM 1.1
No Data Available
Updated: Fri, 6 Mar 2015 20:51 GMT