Re: [Softwires] Questions on: draft-cui-softwire-host-4over6

[Yong Cui <[e-mail]>]

Ole, 

The IPv4/IPv6 address mapping is stateful, which is the almost same as
DS-Lite does on address/port mapping, but simpler (i.e. Without port
mapping). 

Although L3TP is an important tunneling method, do you think IP-IP tunnels
are still widely used, including softwire mesh, DS-Lite, 6RD...? In order
to keep the simplicity, we really hope to use IP-IP tunnels in the
networks.

Yong

-----Original Message-----
From: Ole Troan <[e-mail]>
Date: Thu, 31 Mar 2011 10:44:36 +0200
To: "Lee, Yiu" <[e-mail]>
Cc: "[e-mail] list" <[e-mail]>
Subject: Re: [Softwires] Questions on: draft-cui-softwire-host-4over6

>Yiu,
>
>> Ok. I agree with your definition. How about I rephrase it that dslite
>>and
>> 4over6 don't require control channel. RFC5571 requires control channel.
>> Can we agree that control channel requires extra overhead?
>
>absolutely. both encapsulation and signalling overhead.
>
>that does come with some benefits though, e.g. you can do authentication
>and so on.
>
>cheers,
>Ole
>
>>> Yiu,
>>> 
>>>> The way to set up the tunnel is similar to ds-lite. The CPE will learn
>>>> the
>>>> TC's v6 address, then encap v4 packets into v6 to the TC. To create
>>>>the
>>>> v4-v6 mapping in the TC's routing table. This could be done by the TC
>>>>to
>>>> look at the dhcp message or by keepalive packets from the cpe. We
>>>> haven't
>>>> decided which way is preferred. But the tunnel itself is stateless.
>>> 
>>> since we have tended to classify mechanisms into 'stateless' and
>>> 'stateful'. I think we need a common understanding of what mean by
>>>these
>>> terms.
>>> 
>>> simply stated, if the mechanism scales by the number of
>>> subscribers/tunnels then it is stateful. if it scales by the amount of
>>> packets/traffic then it is stateless.
>>> 
>>> if you agree with that definition I would think 4over6 is stateful,
>>>since
>>> it suggests to integrate the tunnel state into the RIB. i.e. you
>>>allocate
>>> a piece of memory per subscriber and you have to snoop on DHCP messages
>>> to refresh this state.
>>> 
>>> cheers,
>>> Ole
>> 
>
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