rohc team mailing list archive

[Vikram Ragukumar <vragukumar@xxxxxxxxxxxxxx>]

Ahmed,

Such a case would be needed because any two arbitrary endpoints in the 
internet are not separated by a single link/hop. Thus packets might have 
to traverse several links before they reach their destination.
It would be more efficient if compression/decompression did not occur at 
every hop.

Hopefully this clarifies your question, maybe someone else on the group 
can chip in.

Regards,
Vikram.

> Hi,
>
> Why do we need such a case?
> My understanding is that we do the complex algorithms of header 
> compression and accept all this overhead *to save bandwidth on the link 
> layer*, but once the packet arrives to the upper layers of the protocol 
> stack (PC or hand-held device) we need the uncompressed header to 
> process the packet.
>
> Thanks,
> Ahmed
>
> On Wed, May 19, 2010 at 4:39 PM, Cédric Baudoin 
> <baudoin.cedric@xxxxxxxxx <mailto:baudoin.cedric@xxxxxxxxx>> wrote:
>
>     Hi,
>
>     Basically, ROHC is a link layer compression, that is to say that the
>     packets are compressed only on a link (hop by hop if you prefer) and
>     not over the entire internet (end to end).
>     I heard some research activities about end to end compression, but I
>     do not have enough information. Maybe some layer 2 solutions (or
>     2.5) can be found
>
>     Best regards
>
>     Cédric
>
>     2010/5/19 Vikram Ragukumar <vragukumar@xxxxxxxxxxxxxx
>     <mailto:vragukumar@xxxxxxxxxxxxxx>>
>
>         Hello,
>
>         I have a fairly basic question with respect to RoHC. It appears
>         that packets with compressed RTP/UDP/IP headers (chosen as an
>         example profile) do not contain references to source/destination
>         IP addresses.
>
>         How then will such a packet be routed ?
>
>         Does decompression/compression have to take place at every hop
>         so that a routing decision can be made ? If yes, are there any
>         solutions that support end-end header compression, i.e header
>         compression/decompression takes place only at end points
>         corresponding to source/destination IP addresses in original
>         uncompressed IP header.
>
>         Thank you in advance for your help.
>
>         Regards,
>         Vikram.
>
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> --
> Ahmed Abdelrazek
> Embedded Software Developer,
> Non-Access Stratum,
> Research In Motion, Ltd
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