Dear RoHC
ers,
I am having ambiguity regarding "Context memory feedback" option.
I am having ambiguity regarding "Context memory feedback" option.
RFC 3843/ 5225
says:
The CONTEXT_MEMORY option informs the compressor that the decompressor does not
have sufficient memory
resources to handle the context of the packet flow, as the flow is currently compressed.
When receiving a CONTEXT_MEMORY option, the compressor SHOULD take actions to compress the packet flow
in a way that requires less decompressor memory resources or stop compressing the packet flow.
resources to handle the context of the packet flow, as the flow is currently compressed.
When receiving a CONTEXT_MEMORY option, the compressor SHOULD take actions to compress the packet flow
in a way that requires less decompressor memory resources or stop compressing the packet flow.
Q.1) Is
this interpretation in Version1 Profile -0x0004 "Context memory feedback" option
implementation correct?
Lets
say if the Decompressor supports only 2 levels of IP headers in a
compressed packet and could extract only 2
levels
of IP headers from it. But, Compressor supports 3 levels of IP headers and
can compress a 3-level IP Packet and send it to
de-compressor.
In this case decompressor can send "CONTEXT MEMORY FEEDBACK"
Option to compressor indicating insufficient memory resources to
handle.
So, when Compressor receives "Context memory feedback" option, compressor
compresses only 2 levels of IP headers in a 3-level IP Input packet
and send the 3 rd level IP header as part of payload by explicitly terminating
the static chain at 2nd level of IP by setting MSB of Ip-version field
in
2nd level IP to 1.
So,Decompressor can be able to form original header from the compressed packet
as it has enough memory resources to decompress 2-level
IP
compressed packet.
Are there any other ways of compressor handling for this feedback
option.
Pls
suggest me if this interpretation is correct?
Q.2) Where as in Version-2
Profiles, can we reduce the number of IP levels in an Input packet if the
compressor receives
"CONTEXT MEMORY FEEDBACK" option and explicitly indicate the
static chain termination by setting Innermost_IP bit field to
'1'.
But, RFC says Innermost IP level is most correlated to
MSN.
Suppose
if the compressor recieves an input packet with 4-levels of IP
headers followed by an ESP header.
In this case Profile classification will be
PRF-0x0103.
But, if compressor receives "CONTEXT MEMORY FEEDBACK" option, it can
reduce the compressed IP levels as decompressor
doesn't have enough memory resources and sends the remaining IP levels as
Payload. In this case Profile will always be Profile-0x014
as static chain terminates after 3 levels. Can we re-use the existing context in
this case?
Is this interpretation correct?
Please
share your thoughts on the same.
Thanks & Regards,
Chaitanya.
Will the above
implementation give any impact in
Interoperabilty?
Pls share your valuble thoughts regarding the same.
Thanks,
Pradeep.
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