SRv6 NET-PGM extension: Insertion

Introduction Packets transiting an SR Domain may be steered into an SR Policy for a variety of reasons. For example, a PLR router reroutes traffic on a TI-LFA repair path or when a Binding-SID is expanded . This document extends the SRv6 Network Programming model with new endpoint and transit behaviors enabling the insertion of an SRH after the outer IPv6 header of the SR domain. The operations described in this document must take into account the considerations described in .

SRv6 endpoint behaviors SRv6 Network Programming Section 4 defines a base set of SRv6 endpoint behaviors. This is extended with the behaviors described in this section.

End.B6.Insert: Endpoint bound to an SRv6 policy The "Endpoint bound to an SRv6 Policy" is a variant of the End behavior. One of its applications is to express scalable traffic-engineering policies across multiple domains. It is the one of the SRv6 instantiations of a Binding SID . An End.B6.Insert SID is never the last segment in a SID list, and any SID instantiation must be associated with an SR Policy B. When N receives a packet whose IPv6 DA is S and S is a local End.B6.Insert SID, does: max_LE) or (Segments Left > (Last Entry+1)){ S09. Send an ICMP Parameter Problem to the Source Address, Code 0 (Erroneous header field encountered), Pointer set to the Segments Left field, interrupt packet processing and discard the packet S11. } S12. Decrement Hop Limit by 1 S13. Insert a new SRH in between the IPv6 Header and the received SRH containing the list of segments of B S14. Set the IPv6 DA to the first segment of B S15. Resubmit the packet to the egress IPv6 FIB lookup and transmission to the new destination S16. } ]]> When processing the Upper-layer header of a packet matching a FIB entry locally instantiated as an SRv6 End.B6.Insert SID, send an ICMP parameter problem message to the Source Address and discard the packet. Error code "SR Upper-layer Header Error", Pointer set to the offset of the upper-layer header.

End.B6.Insert.Red: [...] with reduced SRH This is an optimization of the End.B6.Insert behavior. End.B6.Insert.Red reduces the size of the new SRH by one SID by avoiding the insertion of the first SID in the pushed SRH. In this way, the first SID is only written in the DA and the packet is forwarded according to it. The new SRH is created as described in Section 4.1.1 of .

SR Policy Headend Behaviors SRv6 Network Programming defines in Section 5 a set of SR Policy Headend Behaviors. This is extended with the following behaviors defined in this section.

H.Insert: SR Headend with insertion of an SRv6 Policy Node N receives two packets P1=(A, B2) and P2=(A,B2)(B3, B2, B1; SL=1). B2 is neither a local address nor SID of N. N steers the transit packets P1 and P2 into an SRv6 Policy with one SID list <S1, S2, S3>. The "H.Insert" transit insertion behavior is defined as follows: Ref1: The received IPv6 DA is placed as last SID of the inserted SRH. Ref1bis: The SRH is inserted before any other IPv6 Routing Extension Header. After the H.Insert behavior, P1 and P2 respectively look like:

(A, S1) (B2, S3, S2, S1; SL=3)
(A, S1) (B2, S3, S2, S1; SL=3) (B3, B2, B1; SL=1)

H.Insert.Red: H.Insert with reduced insertion The H.Insert.Red behavior is an optimization of the H.Insert behavior. It is defined as follows: H.Insert.Red will reduce the size of the SRH by one segment by avoiding the insertion of the first SID in the pushed SRH. In this way, the first segment is only introduced in the DA and the packet is forwarded according to it. After the H.Insert.Red behavior, P1 and P2 respectively look like:

(A, S1) (B2, S3, S2; SL=3)
(A, S1) (B2, S3, S2; SL=3) (B3, B2, B1; SL=1)

Maximum H.Insert MSD Type This document defines the MSD (Maximum SID Depth) for H.Insert behavior and requests the MSD type assignment from the IGP MSD-Types registry created by . The Maximum H.Insert MSD Type specifies the maximum number of SIDs that can be inserted as part of the "H.insert" behavior:

Max H.insert Type: 43 (Suggested value - to be assigned by IANA)

If the advertised value is zero or no value is advertised then the router is assumed not to support any variation of the "H.insert" behavior.

IANA Considerations

SRv6 Endpoint Behaviors This document requests IANA to allocate the following codepoints within the "SRv6 Endpoint Behaviors" sub-registry under the top-level "Segment Routing Parameters" registry. IETF - SRv6 Endpoint Behaviors

Value	Hex	Endpoint behavior	Reference
13	0x000D	End.B6.Insert	[This.ID]
26	0x001A	End.B6.Insert.Red	[This.ID]

MSD Types This document requests IANA to allocate the following codepoint within the "IGP MSD-Types" sub-registry under the top-level "IGP Parameters" registry. IETF - MSD Types

Value	Hex	Endpoint behavior	Reference
43	0x2B	Max H.Insert	[This.ID]

Acknowledgements The authors would like to acknowledge Stefano Previdi, Dave Barach, Mark Townsley, Peter Psenak, Thierry Couture, Kris Michielsen, Paul Wells, Robert Hanzl, Dan Ye, Gaurav Dawra, Faisal Iqbal, Jaganbabu Rajamanickam, David Toscano, Asif Islam, Jianda Liu, Yunpeng Zhang, Jiaoming Li, Narendra A.K, Mike Mc Gourty, Bhupendra Yadav, Sherif Toulan, Satish Damodaran, John Bettink, Kishore Nandyala Veera Venk, Jisu Bhattacharya and Saleem Hafeez.

Contributors Daniel Bernier Bell Canada Canada Email: daniel.bernier@bell.ca Dirk Steinberg Lapishills Consulting Limited Cyprus Email: dirk@lapishills.com Robert Raszuk Bloomberg LP United States of America Email: robert@raszuk.net Bart Peirens Proximus Belgium Email: bart.peirens@proximus.com Hani Elmalky Ericsson United States of America Email: hani.elmalky@gmail.com Prem Jonnalagadda Barefoot Networks United States of America Email: prem@barefootnetworks.com Milad Sharif Barefoot Networks United States of America Email: msharif@barefootnetworks.com David Lebrun Google Belgium Email: dlebrun@google.com Stefano Salsano Universita di Roma "Tor Vergata" Italy Email: stefano.salsano@uniroma2.it Ahmed AbdelSalam Gran Sasso Science Institute Italy Email: ahmed.abdelsalam@gssi.it Gaurav Naik Drexel University United States of America Email: gn@drexel.edu Arthi Ayyangar Arista United States of America Email: arthi@arista.com Satish Mynam Innovium Inc. United States of America Email: smynam@innovium.com Wim Henderickx Nokia Belgium Email: wim.henderickx@nokia.com Shaowen Ma Juniper Singapore Email: mashao@juniper.net Ahmed Bashandy Individual United States of America Email: abashandy.ietf@gmail.com Francois Clad Cisco Systems, Inc. France Email: fclad@cisco.com Kamran Raza Cisco Systems, Inc. Canada Email: skraza@cisco.com Darren Dukes Cisco Systems, Inc. Canada Email: ddukes@cisco.com Patrice Brissete Cisco Systems, Inc. Canada Email: pbrisset@cisco.com Zafar Ali Cisco Systems, Inc. United States of America Email: zali@cisco.com