Subject: [Softwires] 6rd address construction

From: "Lee, Yiu" <[email-masked]>
Date: Wed, 13 Jan 2010 15:23:40 -0500

Hi Mark and Ole,

Few comments: 

1 .In the 03 draft, it shows a "Subnet ID". But the draft didn't mention the
function of it, so I assume this is used by the CE for PD? If you can put
some words what it can be used, this will be great.

2. If the ISP doesn't want to do PD and the result 6rd delegated prefix is
less than /64. What does the CE suppose to do? Should it just zero-pad the
"Subnet-ID"? I think if the draft can give some direction, it will help the
development community.

3. If two CEs in the same domain and want to communicate, the CE "could"
optimize to bypass the 6rd BR. Is this something worth to mention?

Thanks,
Yiu

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From: Ole Troan <[email-masked]>
Date: Wed, 13 Jan 2010 21:30:43 +0100

Yiu,

> some words what it can be used, this will be great.

this is the same subnet ID as in RFC4291, section 2.5.4. I've added a reference now.

> "Subnet-ID"? I think if the draft can give some direction, it will help the

PD is implicit in 6rd. just as you cannot participate in 6to4 without a 6to4 prefix, you also have to have a 6rd prefix. the subnet id is the bits left for the customer site to play with.
so if the 6rd prefix is  a /60 or /56, then the typical scheme is to number all LAN interfaces with a /64 from that prefix. see RFC3633 or the recent draft-ietf-v6ops-ipv6-cpe-router for how that's typically done.

> optimize to bypass the 6rd BR. Is this something worth to mention?

that is the normal way it would work. just like in 6to4. by configuration all communication can go via the BR, but just following the mechanism the BR will only be used for traffic going outside the 6rd domain.

cheers,
Ole

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From: "Lee, Yiu" <[email-masked]>
Date: Wed, 13 Jan 2010 16:04:01 -0500

Ole,

> this is the same subnet ID as in RFC4291, section 2.5.4. I've added a
Thanks.

> PD is implicit in 6rd. just as you cannot participate in 6to4 without a 6to4
> prefix, you also have to have a 6rd prefix. the subnet id is the bits left for
> the customer site to play with.
> so if the 6rd prefix is  a /60 or /56, then the typical scheme is to number
> all LAN interfaces with a /64 from that prefix. see RFC3633 or the recent
> draft-ietf-v6ops-ipv6-cpe-router for how that's typically done.
> 
By saying that, the CE can do whatever it wants for the Subnet ID like the
example shows in RFC 3633.

> that is the normal way it would work. just like in 6to4. by configuration all
> communication can go via the BR, but just following the mechanism the BR will
> only be used for traffic going outside the 6rd domain.
> 
That's fine. I want to add a note that the BR in the 6rd domain must be
provisioned with the IPv4 aggregate if the ISP decides to aggregate the IPv4
prefix. And the 6rd domain to IPv4 aggregate is 1-to-1 map.