Re: [Softwires] Proposed Unified Address Mapping for encapsulation and double-translation

[Rémi Després <[e-mail]>]

Le 6 oct. 2011 à 06:01, GangChen a écrit :

> Hello Remi,
> 
> Thanks for the answers.
> Please see my reply inline.
> 
> 2011/10/5, Rémi Després <[e-mail]>:
>>> There are no necessary to put IPv4 and Port-set ID information in last
>>> 64 bits.
>> 
>> The CE Pv6 prefix included in the /64 Subnet prefix isn't self delimited, so
>> that the length of the CE index can't be determined in this part of the
>> address.
>> Having the length of the A or A+P prefix in the IID completes what is needed
>> to derive the CE port-set.
> 
> I understand such encoded information helps deriving a shared IPv4
> address. However, I guess it's not necessary to dig up such
> information if we only take traffic contronl on IPv6 data plane (as I
> said below)

I agree that it is "not necessary" to exploit this field to filter IPv4 traffic.

Yet it MAY be used to facilitate configuration of traffic control parameters (IPv4 addresses are expressed in clear form instead of having to be derived with the help of mapping rules).
Besides, maintenance is facilitated if IPv4 addresses can be directly read in IPv6 addresses.

  
>>> It may help encapsulation in same cases(e.g. IPv4 based traffic
>>> classification,IPv4 ACL, etc).
>>> However, the translation case is more preferable doing pure IPv6 based
>>> control for the sake of simpler operation reasons (e.g. IPv6 ACL).
>>> It's desirable identifying a customer depending on first 64 bits.
>> 
>> A point is that, although some realistic deployments may ignore what is made
>> available in IIDs (at least at the beginning), some others would take
>> advantage of it.
> 
> Yes. I agree with your point here. As you said such IID design may not
> be taken effect on some realistic deployments, I would like to suggest
> the IID MAY not appeared in double translation cases.

The point is that:
- Copying the IPv4 address at a fixed place in IIDs has a negligible cost.
- Having a SINGLE standard format is cost saving. (I particular, if you don't plan to exploit it at first, you may be glad to have it in the future, at least for maintenance if for nothing else.)

Regards,
RD







> 
> 
> Many thanks
> 
> Gang
>