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Re: [Softwires] MAP Open issues: Interface-id

Ole Troan <ot@cisco.com> Tue, 08 November 2011 08:36 UTC

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From: Ole Troan <ot@cisco.com>
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Date: Tue, 08 Nov 2011 09:36:50 +0100
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To: GangChen <phdgang@gmail.com>
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Cc: Softwires WG <softwires@ietf.org>
Subject: Re: [Softwires] MAP Open issues: Interface-id
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>> 1. Checksum neutrality being an open question, it is relevant here.
>> 2. It is useful AFAIK to distinguish CE addresses from BR addresses.
>> 
>> The best proposal I know so far is as follows (with CNP = Checksum
>> neutrality preserver)
>> 
>> CE ADDRESS
>> 
>> <- - - - - - IPv6 Unformatted  address (104 bits) - - - ->
>> +-------------------+----------+----------+---------------+
>> | Rule IPv6 prefix  |IPv4 suff.| Max PSID |  Padding = 0  |
>> +-------------------+----------+----------+---------------+
>> :
>> :<- - - - - - - - - 64  - - - - - >:<- - - - 40 - - - - ->:
>> :                                  :\                      \
>> :                                  <8>                      :<- 16 ->
>> :                                  : :                      :        :
>> +----------------------------------'-'----------------------+--------+
>> | IPv6 unformatted address (part 1)|V|                      |   CNP  |
>> 
>> +----------------------------------+-+----------------------+--------+
>> <- - - - - - - - - - -  IPv6 address (108 bits)  - - - - - - - - - - >
>> 
>> 
>> 
>> BR ADDRESS
>> 
>> +------------------------------------+-+-----------------+-+-------+
>> |              BR IPv6 prefix        |V|   IPv4 address  |0|  CNP  |
>> +------------------------------------+-+-----------------+-+-------+
>> < - - - - - - - - - 64  - - - - - - ><8><- - -  32 - - -><8><  16  >
>> 
> 
> +1
> The checksum neutrality is desirable for translation case.
> I suggest to take above format into consideration

the consequence of that is that the destination IPv6 address will change for every flow.
the MAP node cannot any longer listen to a single IPv6 address for MAP traffic, but has to intercept packets for a whole prefix.

cheers,
Ole

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