Ron Bonica <mailto:rbonica=40juniper....@dmarc.ietf.org>
1 September 2019 at 22:10
Hi Fernando,
6man participants should look at the following:
-
https://tools.ietf.org/html/draft-ietf-spring-srv6-network-programming-01
(In particular, Sections 4 and 5)
-
https://tools.ietf.org/html/draft-filsfils-spring-net-pgm-extension-srv6-usid-02
Ron
Juniper Business Use Only
-----Original Message-----
From: Fernando Gont <fg...@si6networks.com>
Sent: Saturday, August 31, 2019 4:53 PM
To: Ron Bonica <rbon...@juniper.net>; Rob Shakir <ro...@google.com>;
SPRING WG List <spring@ietf.org>; 6...@ietf.org
Subject: Re: [spring] Beyond SRv6.
Hi, Ron,
For those 6man-ers that have not been following the sprin work, could
you please clarify what do you mean by "stretching the interpretation of
RFC8200 or RFC4291"?
In the past we have seen outright violation of RFC8200 (formerly
RFC2460), so I'm curious if there are any documents trying to do the
same, or what.
Thanks!
Cheers,
Fernando
--
Fernando Gont
SI6 Networks
e-mail: fg...@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492
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Fernando Gont <mailto:fg...@si6networks.com>
31 August 2019 at 21:53
Hi, Ron,
For those 6man-ers that have not been following the sprin work, could
you please clarify what do you mean by "stretching the interpretation of
RFC8200 or RFC4291"?
In the past we have seen outright violation of RFC8200 (formerly
RFC2460), so I'm curious if there are any documents trying to do the
same, or what.
Thanks!
Cheers,
Fernando
Ron Bonica <mailto:rbonica=40juniper....@dmarc.ietf.org>
31 August 2019 at 21:33
Rob,
The following are arguments for proceeding with SRv6+:
* Efficient forwarding with deep SID lists
* Operational Simplicity
* SRv6+ work may finish before SRv6
Efficient forwarding with deep SID Lists
----------------------------------------------------
SR customers have stated a firm requirement to support SR paths that
contain 8 to 12 segments. They have also stated a requirement for
implementations to forward at line speed and without consuming
excessive overhead bandwidth.
SRv6, as defined in draft-ietf-6man-segment-routing-header, cannot
satisfy these requirements. In order to support an SR path with 8
segments, SRv6 would require a 128-byte SRH. Even if ASICs could
process such a long SRH at line speed, the bandwidth overhead would be
prohibitive.
Therefore, one of the four solutions that you mention below is
required to make SRv6 deployable. While
draft-ietf-6man-segment-routing-header is close to maturity, the four
competing solutions mentioned below are equally mature and should be
given equal consideration.
The four solutions are SRv6+, uSID, draft-li and draft-mirsky.
Operational Simplicity
-----------------------------
Network operators strive for operational simplicity. By loosely
interpreting (and sometimes bending) the requirements of RFCs 4291 and
RFC 8200, SRv6 introduces architectural quirks that introduce
operational complexity. The following are architectural quirks of
draft-ietf-6man-segment-routing-header:
* The Segment Routing Header (SRH) serves purposes other than
routing. Therefore, the SRH is sometimes required for packets that
traverse the least-cost path from source to destination
* The SRH and the IPv6 Authentication Header are incompatible.
* The IPv6 destination address determines whether an SRH is valid
and how it is processed. For example, if the IPv6 destination
address contains one locally instantiated value, the SRH might be
processed in one particular way, while if the IPv6 destination
address contains another locally instantiated value, the SRH might
be totally invalid.
Draft-ietf-spring-srv6-network-programming promises more
architectural quirks. For example:
* Segment endpoints can insert and/or delete IPv6 extension headers
* An IPv6 packet can contain two Segment Routing headers
* IPv6 packets are no longer self-describing. For example, the Next
Header Field in the SRH can carry a value of No Next Header, even
though the SRH is followed by Ethernet payload.
Other emerging drafts promise still more architectural quirks. For
example, in draft-ali-6man-spring-srv6-oam, implementations need to
examine the SRH even when Segment Left equals zero. This is because
the SRH has been overloaded to carry OAM as well as routing information.
Furthermore, draft-filsfils-spring-net-pgm-extension-srv6-usid
requires network operators to obtain address space and number their
networks in a particular way to make routing work.
SRv6+ Work May Finish Before SRv6 work
--------------------------------------------------------
SRv6+ has been implemented on LINUX and is being implemented on
JUNOS. Implementation experience demonstrates that specification is
fairly complete. For example, there is no need for an SRv6+ OAM
document. It’s just IPv6 and IPv6 OAM just works.
Furthermore, the SRv6+ specifications adhere to a strict
interpretation of RFC 8200. Therefore, as they progress through the
working group, they won’t need to overcome the objections that are
inevitably encountered when stretching the interpretation of a
specification that is so fundamental as RFC 8200.
Thanks,
Ron
*From:* spring <spring-boun...@ietf.org> *On Behalf Of *Rob Shakir
*Sent:* Sunday, August 4, 2019 5:04 PM
*To:* SPRING WG List <spring@ietf.org>
*Subject:* [spring] Beyond SRv6.
Hi SPRING WG,
Over the last 5+ years, the IETF has developed Source Packet Routing
in NetworkinG (SPRING) aka Segment Routing for both the MPLS (SR-MPLS)
and IPv6 (SRv6) data planes. SR-MPLS may also be transported over IP
in UDP or GRE.
These encapsulations are past WG last call (in IESG or RFC Editor).
During the SPRING WG meeting at IETF 105, two presentations were
related to the reduction of the size of the SID for IPv6 dataplane:
* SRv6+ / CRH --
https://tools.ietf.org/html/draft-bonica-spring-srv6-plus-04
<https://urldefense.proofpoint.com/v2/url?u=https-3A__tools.ietf.org_html_draft-2Dbonica-2Dspring-2Dsrv6-2Dplus-2D04&d=DwMFaQ&c=HAkYuh63rsuhr6Scbfh0UjBXeMK-ndb3voDTXcWzoCI&r=Fch9FQ82sir-BoLx84hKuKwl-AWF2EfpHcAwrDThKP8&m=ackZC9evRf_LWYu2a-1NaGRDJKdxnE2ieIC4dD_FL6s&s=KUhAfjVsx_wK645uJk0FHzs2vxiAVr-CskMPAaEhEQQ&e=>
* uSID --
https://tools.ietf.org/html/draft-filsfils-spring-net-pgm-extension-srv6-usid-01
<https://urldefense.proofpoint.com/v2/url?u=https-3A__tools.ietf.org_html_draft-2Dfilsfils-2Dspring-2Dnet-2Dpgm-2Dextension-2Dsrv6-2Dusid-2D01&d=DwMFaQ&c=HAkYuh63rsuhr6Scbfh0UjBXeMK-ndb3voDTXcWzoCI&r=Fch9FQ82sir-BoLx84hKuKwl-AWF2EfpHcAwrDThKP8&m=ackZC9evRf_LWYu2a-1NaGRDJKdxnE2ieIC4dD_FL6s&s=Aq1DK7fu73axZ1PXLIE8xnHE2AhTtNZy9LTHgWqx4CQ&e=>
During the IETF week, two additional drafts have been proposed:
* https://tools.ietf.org/html/draft-li-spring-compressed-srv6-np-00
<https://urldefense.proofpoint.com/v2/url?u=https-3A__tools.ietf.org_html_draft-2Dli-2Dspring-2Dcompressed-2Dsrv6-2Dnp-2D00&d=DwMFaQ&c=HAkYuh63rsuhr6Scbfh0UjBXeMK-ndb3voDTXcWzoCI&r=Fch9FQ82sir-BoLx84hKuKwl-AWF2EfpHcAwrDThKP8&m=ackZC9evRf_LWYu2a-1NaGRDJKdxnE2ieIC4dD_FL6s&s=XWUDAD2FMhWLfeT5sgUb1lgthJhugcyT98GJ2N-CrKs&e=>
* https://tools.ietf.org/html/draft-mirsky-6man-unified-id-sr-03
<https://urldefense.proofpoint.com/v2/url?u=https-3A__tools.ietf.org_html_draft-2Dmirsky-2D6man-2Dunified-2Did-2Dsr-2D03&d=DwMFaQ&c=HAkYuh63rsuhr6Scbfh0UjBXeMK-ndb3voDTXcWzoCI&r=Fch9FQ82sir-BoLx84hKuKwl-AWF2EfpHcAwrDThKP8&m=ackZC9evRf_LWYu2a-1NaGRDJKdxnE2ieIC4dD_FL6s&s=gcbkHYxXm7FU7vblOB1vI58SDaaWf62pa7YvLmsP4nI&e=>
As we expressed during the meeting, it is important for the WG to
understand what the aims of additional encapsulations are. Thus, we
think it is important that the WG should first get to a common
understanding on the requirements for a new IPv6 data plane with a
smaller SID - both from the perspective of operators that are looking
to deploy these technologies, and from that of the software/hardware
implementation.
Therefore, we would like to solicit network operators interested in SR
over the IPv6 data plane to briefly introduce their:
* use case (e.g. Fast Reroute, explicit routing/TE)
* forwarding performance and scaling requirements
o e.g., (number of nodes, network diameter, number of SID
required in max and average). For the latter, if possible
using both SRv6 128-bit SIDs and shorter (e.g. 32-bit) SIDs as
the number would typically be different (*).
* if the existing SRv6 approach is not deployable in their
circumstances, details of the requirement of a different solution
is required and whether this solution is needed for the short term
only or for the long term.
As well as deployment limitations, we would like the SPRING community
to briefly describe the platform limitations that they are seeing
which limit the deployment of SRv6 In particular limitations related
to the number of SIDs which can be pushed and forwarded and how much
the use of shorter SIDs would improve the deployments .
For both of these sets of feedback if possible, please post this to
the SPRING WG. If the information cannot be shared publicly, please
send it directly to the chairs & AD (Martin).
This call for information will run for four weeks, up to 2019/09/03.
As a reminder, you can reach the SPRING chairs via
spring-cha...@ietf.org <mailto:spring-cha...@ietf.org>and ADs via
spring-...@ietf.org <mailto:spring-...@ietf.org>.
Thank you,
-- Rob & Bruno
(*) As expressed on the mailing list, a 128 bit SID can encode two
instructions a node SID and an adjacency SID hence less SID may be
required.
Juniper Business Use Only
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