operating assumptions (section 4.1)

[zhigang.liu@nokia.com]

Hello Folks,

In the current rohc draft (ver 01), there are two sections that seem
to be redundant to each other: 4.1. Operating assumptions and 
4.6. Requirements on lower layers.

I guess it's probably an unintentional result of on-going editorial 
work when we merged different proposals, as the case for many other 
sections. Since lower layer guideline will address the issues in a 
separate draft, I'd like to suggest that we keep the section 4.1 
"operating assumptions" and remove section 4.6.

I list at the end of this email some assumptions that are at least 
needed for rohc protocol. Please give comments on whether they are 
sufficient, so that we can finalize this section.

I'm also working on the 4.5 encoding methods (merging texts addressing
the same issue, adding some text e.g. offset IP-ID encoding, etc). It
will probably be ready next Monday. 

Br,
Zhigang

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4.1.  Operating assumptions

packet length: the link layer can provide the length of a compressed packet.

(it is beneficial but not required to provide the length of a feedback
packet)

error detection: the link layer can provide reasonably good error detection 
for compressed headers and feedback packets. (Error protection is 
beneficial but not required.)

in order delivery: the link layer between the compressor and decompressor 
preserves the order of packets being transmitted, i.e. the decompressor 
(compressor) will receives the packets in the order they were sent by the 
compressor (decompressor). (Note that packet misordering before compressor
can be handled by rohc protocol)