Re: [OSPF] [Isis-wg] [sunset4] IPv6 router IDs

[Acee Lindem <[e-mail]>]

Xiaohu – what are precisely the situations that you think you need this IPv6 address?
Acee

From: Xuxiaohu <[e-mail]<mailto:[e-mail]>>
Date: Sunday, May 4, 2014 1:29 AM
To: "George, Wes" <[e-mail]<mailto:[e-mail]>>
Cc: OSPF - OSPF WG List <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>
Subject: Re: [Isis-wg] [sunset4] IPv6 router IDs

Hi Wes,

Thanks for pointing out these two drafts.

The motivation for these two drafts (http://tools.ietf.org/html/draft-xu-isis-ipv6-router-id-00 and http://tools.ietf.org/html/draft-xu-ospf-ipv6-router-id-00) is very simple: the IPv6 ISIS|OSPF capability TLV/RI-LSA which are used for advertising router capabilities can be flooded across areas, however, only a 4-octect router ID is carried in them. As a result, it’s hard for routers in one area to establish correlations between IPv6 addresses and capabilities of routers in another area. For example, assume IS-IS router A in one area has established a L3VPN session with IS-IS router B in another area over their own IPv6 addresses. When router A needs to send L3VPN traffic to router B via a MPLS-SR tunnel, router A wants to know whether router B has the ELC (http://tools.ietf.org/html/draft-xu-isis-mpls-elc-00) before<http://tools.ietf.org/html/draft-xu-isis-mpls-elc-00)%20before> inserting an EL into the MPLS-SR packet . However, the Capability TLV originated by router B doesn’t carried an IPv6 address of its own. As a result, it’s hard for router A to know the ELC of router B.

Best regards,
Xiaohu

发件人: George, Wes [mailto:[e-mail]]
发送时间: 2014年5月2日 1:51
收件人: Xuxiaohu
抄送: [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
主题: Re: [sunset4] IPv6 router IDs

I got a bounce-back on all 3 draft aliases, trying again with the authors’s email addresses directly.

From: <George>, "George, Wes" <[e-mail]<mailto:[e-mail]>>
Date: Thursday, May 1, 2014 at 1:42 PM
To: "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>
Cc: "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>
Subject: [sunset4] IPv6 router IDs

I see that you have submitted two drafts for IPv6 router IDs in ISIS and OSPF, noting that the existing router ID is only 4 octets. This has also come up in IDR for BGP. The authors of that draft are copied. I’ll give you a similar set of feedback to what I gave them -

It is important to distinguish between places where a unique identifier is needed, and by convention an IPv4 address assigned to the device has been used to provide that unique ID, vs. places where the actual IP address has some sort of importance to the protocol (I.e. That information must be available to take action on).
In other words, is the protocol requirement that the ID be unique across some domain, but that the actual value does not matter, or is the protocol requirement that the value must correspond to something on the router? In many of the former cases, the fact that the value isn’t relevant has been used to make recommendations that are easier for humans to deal with (I.e. Tying the router ID to an IP address) but that value as a human-readable set of info does not necessarily justify  changes to the protocol to support that convention as we move to IPv6.
I would argue that the router ID used in routing protocols must merely be unique, but it doesn’t have to be an IP address at all. Thus it is not strictly necessary to create a new field to carry IPv6 addresses when operating without IPv4 addresses on a network. If you believe otherwise, the justification needs to be documented in the draft.

There are many places in IETF protocols where a 32 bit unique identifier is needed, and by convention an IPv4 address has been used. It would be far more useful to write a general draft identifying this problem and discussing several solutions, including simply generating unique IDs manually, systematically generating a random ID, etc.  the place for such a draft may be in Sunset4, either as a part of the existing gap analysis draft or as another standalone draft.

There was rather a long discussion about this on IDR, thread here: https://mailarchive.ietf.org/arch/search/?qdr=a&email_list=idr&q=%22%5Bidr%5D+%5Bv6ops%5D+BGP+Identifier%22&as=1&gbt=1

And in the IDR meeting, minutes:
http://www.ietf.org/proceedings/89/minutes/minutes-89-idr (see page 11)

I’d encourage the authors of these drafts to work together on this.

Thanks,

Wes George

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