Re: [spring] 6MAN WGLC: draft-ietf-6man-sids

[Suresh Krishnan <[e-mail]>]

Hi Gyan,
  Thanks for your comments. Please find responses inline.

> On Sep 28, 2022, at 11:06 PM, Gyan Mishra <[e-mail]> wrote:
> 
> 
> I support publication of the draft.
> 
> I have reviewed the draft and have some comments.
> 
> As the C-SID draft had been adopted by Spring I don’t see a need for section 4.2 as is not relevant.
> 
> Section 4 talks about C-SID which is vague as it should be referencing the two different vendor solutions below:

Good point. I have a queued up change from early in the WGLC to update the reference to draft-ietf-spring-srv6-srh-compression which is the spring WG draft and that would obviate the need to add vendor specific solutions.

> 
> Brief description of each flavor and operation I think is important for the draft.
> 
> 1. Cisco uSID micro sid - Next function- Shift by 16 bits and forward at each node endpoint processing. 
> The 128 bit DA is a  uSID carrier can have up to 6 16 bit uSIDs encoded into the DA for steering up to 6 nodes without SRH.  If desirable to steer to more then 6 nodes an SRH is required along with SR Policy with Segment list.
> 
> 2. Huawei G-SID - Replace function - Copies G-SID from SRH to DA address at each node endpoint processing.  G-SID operation requires SRH present.
> 
> Most all deployments of SRV6 are done using ULA addressing RFC 4193.  Even across the internet the internal P nodes in a carrier network can use RFC 4193 as along as the eBGP peering points use next hop self which avoids requiring next hop eBGP subnet accessibility.  That being said subnets or even aggregate summary of the carrier network does not need to be advertised outside of the carrier networks domain.
> 
> This draft proposed an IANA allocation /16 for the GUA address for the SRv6 block B:N deployment out of which the SRv6 locators are allocated.  
> 
> I understand the reasoning behind it to avoid advertisement of the locators outside of the domain.
> 
> The IANA allocation does not mention that the block should be made non internet routable  like a ULA. 

Yes. The IANA allocation itself will not have such properties as the registry does not have a way to request it.

https://www.iana.org/assignments/ipv6-address-space/ipv6-address-space.xhtml <https://www.iana.org/assignments/ipv6-address-space/ipv6-address-space.xhtml>

But we can certainly add an entry to https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml <https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml> to mention this is in fact the case.

I also see that the discussion about using ULA instead of a specific prefix has progressed on and I have a view that is very similar to what Brian C. and Michael R. had expressed.

Regards
Suresh