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

[stephane.litkowski]

Hi Rajiv,

IMO, I don’t think that “Inferring it from AFI/SAFI per section 3 of RFC4760” 
means that there is a format match between the NH field and NLRI, it just says 
that there is a relation between the AFI/SAFI and the protocol layer of the NH.
When you know the AFI/SAFI, you can deduce the NH encoding based on the NH 
encoding rules defines for this particular AFI/SAFI. RFC4760 doesn’t say that 
there is an exact match between NLRI format and NH format.

“The Network Layer protocol associated with the Network Address of
 the Next Hop is identified by a combination of 
 carried in the attribute.”

Brgds,

Stephane

From: BESS [mailto:bess-boun...@ietf.org] On Behalf Of Rajiv Asati (rajiva)
Sent: Thursday, June 27, 2019 13:37
To: Robert Raszuk
Cc: i...@ietf.org; Xiejingrong; Alexander Okonnikov; softwi...@ietf.org; 
bess@ietf.org; draft-dawra-bess-srv6-servi...@ietf.org
Subject: Re: [bess] [Softwires] [Idr] Regarding the Next Hop Network Address 
coding for IPv4 VPN over IPv6 Core in RFC5549


I agree and sometimes flexibility becomes an unwanted necessity (as is the case 
here with option (a)).

IMO, option (b) length based check for NH should be preferred, since it works 
for all AFI/SAFIs with an assumption that NH could be one IPv4 or IPv6 prefix. 
Very reasonable option.

Option (a) AFI/SAFI based interpretation doesn’t work for all AFI/SAFIs that 
don’t distribute non-routing information  e.g. policy, capabilities, LS etc.

Cheers,
Rajiv


On Jun 27, 2019, at 6:50 AM, Robert Raszuk 
mailto:rob...@raszuk.net>> wrote:
> 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.

When elements of BGP UPDATE message are being parsed code must know what to 
expect. Note that we are dealing here with deployed SAFI 128 for nearly 20 
years.

So today there are two ways to know what format of next hop is in MP_REACH:

a) Inferring it from AFI/SAFI per section 3 of RFC4760

or (in addition to the above coarse assumption)

b) Inferring it from the discrete value of next hop length field as defined in 
section 3 of RFC5549

Note that if we would be defining new SAFI we can write anything we like to the 
rules of constructing the update message. But here again we are dealing with 
something which is deployed so sort of operating on the plane in flight.

If implementation can infer next hop type from length we are safe to define all 
sections to have next hop length = 16 octets and be done. But if there are some 
implementations which would only take AFI/SAFI to check if the next hop is 
correct or even further to check if the next hop length is correct then we have 
a problem.

/* Btw this notion of next hop length = 32 is bizarre ! I have never seen any 
BGP implementation sending two next hops (global IPv6 address followed by link 
local IPv6 address) not I am able to find any docs describing how any BGP stack 
would handle it. IMHO we should move this 32 next hop length to historic asap. 
*/

To the msg from Martin,

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

I would vote to reject the errata. There is no value of stuffing 8 octet of 
zeros in the next hop field. If the RFC got defined in 2012 that really means 
that most implementations are capable of inferring next hop format from the 
length field - which is very good. Accepting the errata would be a step 
backwords.

Thx,
R.

On Thu, Jun 27, 2019 at 11:15 AM Xiejingrong 
mailto:xiejingr...@huawei..com>> wrote:
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>>; 

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

[Robert Raszuk]

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 
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 ; Alexander Okonnikov <
> alexander.okonni...@gmail.com>; Robert Raszuk ;
> 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 
> > *Cc:* UTTARO, JAMES ; Xiejingrong
> > ; 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!
> >
> >
> >
> >
> >
> > ___
> > Idr mailing list
> > i...@ietf.org
> > https://www.ietf.org/mailman/listinfo/idr
> >
> ___
> Softwires mailing list
> softwi...@ietf.org
> https://www.ietf.org/mailman/listinfo/softwires
> ___
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> https://www.ietf.org/mailman/listinfo/bess
>
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