Re: [bess] [Softwires] [Idr] Regarding the Next Hop Network Address coding for IPv4 VPN over IPv6 Core in RFC5549

[ian.farrer]

Hi,

(co-chair hat off)

I also vote to reject this erratum on the following grounds: The erratum text 
was raised as:

Section 6.2 says:
Length of Next Hop Network Address = 16 (or 32)
It should say:
Length of Next Hop Network Address = 24 (or 48)
Notes:
The lengths should include the RD length also, right ?

However, RFC5549 specifies in several places that the next-hop address is of 
type IPv6 address (Sections 3, 4, 6.1 and 6.2). The use of an IPv6 address as 
the next hop was clearly the intention of the author and the document was 
reviewed and published as such. The existing text in section 6.2 (Length of 
Next Hop Network Address = 16 (or 32)) is consistent with this and changing it 
as proposed in the would only introduce an inconsistency.

Thanks,
Ian

From: Softwires  on behalf of Robert Raszuk 

Date: Thursday, 27. June 2019 at 13:53
To: Zhuangshunwan 
Cc: "i...@ietf.org" , Alexander Okonnikov 
, "softwi...@ietf.org" , 
"Vigoureux, Martin (Nokia - FR/Paris-Saclay)" , 
"bess@ietf.org" 
Subject: Re: [Softwires] [bess] [Idr] Regarding the Next Hop Network Address 
coding for IPv4 VPN over IPv6 Core in RFC5549


My vote - Reject.

Justification:

Irrespective if we would reject or accept the erratum implementations must be 
able to handle 10 years old RFC so must be able to properly recognize the next 
hop to be either of length 16 or 24. (I am putting aside the 32/48 invention)..

So that means that next hop length should be used to recognize format of the 
next hop. That with the fact that stuffing next hop address with useless 64 
zeros in the front leads me to believe that if we are to produce any erratums 
it should be the other way around ... we should replace all documents which 
call for having next hops full of zeros in the front to normalize it to consist 
of just real IPv4 or IPv6 single address.

Thx,
R.

On Thu, Jun 27, 2019 at 1:39 PM Zhuangshunwan 
mailto:zhuangshun...@huawei.com>> wrote:
Hi all,

Can the WG reach a conclusion on how to treat that erratum related to RFC5549:

https://www.rfc-editor.org/errata/eid5253

Thanks,
Shunwan

-Original Message-
From: Softwires 
[mailto:softwires-boun...@ietf.org] On 
Behalf Of Vigoureux, Martin (Nokia - FR/Paris-Saclay)
Sent: Thursday, June 27, 2019 6:37 PM
To: Xiejingrong mailto:xiejingr...@huawei.com>>; 
Alexander Okonnikov 
mailto:alexander.okonni...@gmail.com>>; Robert 
Raszuk mailto:rob...@raszuk.net>>; 
bess@ietf.org
Cc: softwi...@ietf.org; 
i...@ietf.org
Subject: Re: [Softwires] [Idr] [bess] Regarding the Next Hop Network Address 
coding for IPv4 VPN over IPv6 Core in RFC5549

since we are discussing that topic,

maybe the WG would like to reach a conclusion on how to treat that erratum:
http://www.rfc-editor.org/errata/eid5738

Thanks
-m

Le 2019-06-27 à 11:15, Xiejingrong a écrit :
> Thanks for the RFC historical lessons.
>
> --there was historically some assumption that next hop must be of the
> same AF as prefix.
>
> --RFC 2858 says that Next Hop field should match AFI. On the other
> hand, RFC 4760 says that Next Hop Field should match combination of AFI/SAFI.
>
> --authors of RFC 4364 were trying to make it consistent with 4760.
>
> --Also, drafts of RFC 4364 and RFC 4760 were being developed
> practically at the same time period.
>
> The problem is clear, the nexthop field has been inconsistent between
> different L3VPN/MVPN scenarios and different implementations in the
> long history.
>
>  is the latest draft, but it has
> different nexthop in section 3.1 to 3.4, in the year 2019.
>
> Back to my suggestion: implementation should interpret nexthop RD+IPv4
> and nexthop IPv4 the same, and interpret nexthop RD+IPv6 and nexthop
> IPv6 the same.
>
> I think it may be helpful for  to
> add the above text, and update RFC4364/4659/4760/5549, to eliminate
> the worries about interoperation. is there any worries about
> interoperation ?
>
> Thanks
>
> Jingrong
>
> *From:*Alexander Okonnikov 
> [mailto:alexander.okonni...@gmail.com]
> *Sent:* Wednesday, June 26, 2019 9:38 PM
> *To:* Robert Raszuk mailto:rob...@raszuk.net>>
> *Cc:* UTTARO, JAMES mailto:ju1...@att.com>>; Xiejingrong
> mailto:xiejingr...@huawei.com>>; 
> softwi...@ietf.org; 
> i...@ietf.org;
> ian.far...@telekom.de; 
> bess@ietf.org; 
> ianfar...@gmx.com
> *Subject:* Re: [Idr] [bess] [Softwires] Regarding the Next Hop Network
> Address coding for IPv4 VPN over IPv6 Core in RFC5549
>
> Hi Robert,
>
> Sorry, I was not so precise :-) Of course, RD part in Next Hop is not
> copied from RD of NLRI, but zeroed. I was trying to explain why Next
> Hop field in RFC 4364 and RFC 4659 has format RD:IP (VPNvX address)
> rather than just IP.
>
> Thank you!
>
>
>
>
>
> 

Re: [bess] [Softwires] Regarding the Next Hop Network Address coding for IPv4 VPN over IPv6 Core in RFC5549

[ian.farrer]

Hi Shunwan,

I’ve just re-checked RFC5539, and the referenced section 3 of RFC2545 and I can 
find nothing about using VPN-IPv6 for encoding the next-hop. Section 3 of 
RFC5539 is very clear that it’s a 16-byte GU IPv6 address or 32-bytes with a GU 
and LL address.

Can you point me to the text that gives you the impression that VPN-IPv6 is 
correct?

Note – I see that there is reported Errata on RFC5549, (not verified) saying 
that the length should be 24 or 48 to include the RD. However, as mentioned 
above, the supporting text in multiple places in the RFC and its references 
support the use of an IPv6 address (or 2) with no RD at 16 or 32 bytes, so this 
does seem to be the intention of the document as written.
https://www.rfc-editor.org/errata_search.php?rfc=5549

Thanks,
Ian

From: Softwires  on behalf of Zhuangshunwan 

Date: Tuesday, 25. June 2019 at 13:18
To: "ianfar...@gmx.com" 
Cc: "softwi...@ietf.org" , "bess@ietf.org" 
Subject: Re: [Softwires] Regarding the Next Hop Network Address coding for IPv4 
VPN over IPv6 Core in RFC5549

Hi Ian,

Thanks for your response!

The opinion I have collected is:
Per RFC4634, the IPv4-VPN routes shall carry the V4 Next-hop, beginning with an 
8-octet RD and ending with a 4-octet IPv4 address.
Per RFC4659, the IPv6-VPN routes shall carry the V6 Next-hop, beginning with an 
8-octet RD and ending with a 16-octet IPv6 address.
When we start to implement the IPv4 VPN over IPv6 Core,  it is a natural way to 
encode the IPv4-VPN routes with VPN-IPv6 next-hop (i.e. beginning with an 
8-octet RD and ending with a 16-octet IPv6 address) .

I believe this is not just a minority opinion, and some of the current 
implementations are also doing this way.

I hope that the WGs can give a consistent opinion on this issue and avoid 
interoperability problem in the future.

Thanks,
Shunwan

From: ianfar...@gmx.com [mailto:ianfar...@gmx.com]
Sent: Monday, June 24, 2019 8:08 PM
To: Zhuangshunwan 
Cc: bess@ietf.org; softwi...@ietf.org
Subject: Re: [Softwires] Regarding the Next Hop Network Address coding for IPv4 
VPN over IPv6 Core in RFC5549

Hi,

My reading of Section 3 of RFC5549 is that the v6 next-hop is encoded as an 
IPv6 address:

   The BGP speaker receiving the advertisement MUST use the Length of
   Next Hop Address field to determine which network-layer protocol the
   next hop address belongs to.  When the Length of Next Hop Address
   field is equal to 16 or 32, the next hop address is of type IPv6.

It’s also worth noting that RFC4659 Section 2 states:

A VPN-IPv6 address is a 24-octet quantity, beginning with an 8-octet
   "Route Distinguisher" (RD) and ending with a 16-octet IPv6 address.

So, not 16 or 32 bytes.

Thanks,
Ian




On 22. Jun 2019, at 09:59, Zhuangshunwan 
mailto:zhuangshun...@huawei.com>> wrote:

Dear authors and WGs,

RFC5549 Section 6.2 says:

. 6.2.  IPv4 VPN over IPv6 Core
.
.The extensions defined in this document may be used for support of
.IPV4 VPNs over an IPv6 backbone.  In this application, PE routers
.would advertise VPN-IPv4 NLRI in the MP_REACH_NLRI along with an IPv6
.Next Hop.
.
.The MP_REACH_NLRI is encoded with:
.
.o  AFI = 1
.
.o  SAFI = 128
.
.o  Length of Next Hop Network Address = 16 (or 32)
.
.o  Network Address of Next Hop = IPv6 address of Next Hop
.
.o  NLRI = IPv4-VPN routes


Regarding IPv4-VPN routes, RFC4634 Section 4.3.2 says:

. 4.3.2.  Route Distribution Among PEs by BGP
[snip]
.When a PE router distributes a VPN-IPv4 route via BGP, it uses its
.own address as the "BGP next hop".  This address is encoded as a
.VPN-IPv4 address with an RD of 0.  ([BGP-MP] requires that the next
.hop address be in the same address family as the Network Layer
.Reachability Information (NLRI).)  It also assigns and distributes an
.MPLS label.  (Essentially, PE routers distribute not VPN-IPv4 routes,
.but Labeled VPN-IPv4 routes.  Cf. [MPLS-BGP].)  When the PE processes
.a received packet that has this label at the top of the stack, the PE
.will pop the stack, and process the packet appropriately.
[snip]


Question:
RFC5549 defines "IPv4 VPN over IPv6 Core", When a PE router distributes a 
VPN-IPv4 route with an IPv6 Next-Hop via BGP, should the IPv6 Next-Hop be 
encoded as an VPN-IPv6 address with an RD of 0 ?


Thanks,
Shunwan
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