Re: [spring] Beyond SRv6.

[Yuji Kamite <[e-mail]>]

Hi folks,

Let me post the feedback of requirement as an operator.

Best regards,
-Yuji

---
Use Cases:
 1. Explicit Routing(TE) – replacement/successor to the existing MPLS.
  2. TI LFA / FastReroute -- same as above.  link and node protection
  3. VPN service --  same as above. EVPN and/or IP-VPN.
  4. NW Slicing   -- separate network logically, depending on traffic characteristics, with more fine-grained manner.
  5. Service Function Chaining -- multiple VNF/CNFs are provisioned and dynamically connected, mostly in NFV infrastructure
  6. Migration from SR-MPLS to SRv6
  We already have deployment using 1 to 3.  4 to 6 are also planned things.  In my view, SRv6 large-scale deployment is still limited today.


Requirements:
 1. Number of nodes / SIDs required:
    Existing production network:   < 5 hops in Datacenters,  < 10 hops average in WAN networks
As long as we use simple VPN and TI-LFA only by SRv6,  supporting a few number of SID stack is still fine; however, it is obvious that other use cases cannot be realized.
    From now on with SR:  at least 10 segments support required,.10-15 is desired, .(I think it would not be longer than 20 soon though), when considering:
    - Connecting various metro MEC/5G backhauling network to the center network
    - Connecting IPSec/SD-WAN overlay access
    - Service function chaining across multiple locations
    - Traffic metering based on different slices
    - With several steering hops added (for example, monitoring traffic with steering)

 2. Forwarding and Performance
      We have two major concern about current SRv6:
   (a) Bandwidth consumption overhead (issue in the existing SRv6 with 128bit SID)
   (b) Performance of forwarding equipment (typically the limitation of chip )
  (Note: (b) depends on each vendor's implementation.  I cannot mention each vendor's limitation information here, but I think it is important for community to share the understanding about today’s achievable level of number of SIDs/ performance limit in the industry.)

3. Length of SIDs needed
      - 16bits or 32bits (note: 32bit can be considered almost the same level as MPLS-SR)

4. Network design (e.g., physical MTU design) flexibility
      - Operators do not want complex design of topology and MTU considering the increase of SIDs in the future.

5. Multi domain network support
      - Multi-Area. Multi-AS support

6. Addressing flexibility
      - For providers who have the existing IPv6 deployment, a solution should avoid their drastic change of their current addressing.

7. Route information scalability
      - Additional propagation of IGP routes should be minimized as much as possible.

8. OAM functionality
     - Should provide OAM such as Ping/Traceroute for troubleshooting and failure detection/isolation.
     - It is desired that a solution can use ordinary ICMP mechanism (partially or fully) because it is a natural scenario that non-SR capable v6 domains are included in SRv6 end-end path.
----



From: spring <[e-mail]> On Behalf Of Rob Shakir
Sent: Monday, August 5, 2019 6:04 AM
To: SPRING WG List <[e-mail]>
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
  *   uSID -- https://tools.ietf.org/html/draft-filsfils-spring-net-pgm-extension-srv6-usid-01


During the IETF week, two additional drafts have been proposed:

  *   https://tools.ietf.org/html/draft-li-spring-compressed-srv6-np-00
  *   https://tools.ietf.org/html/draft-mirsky-6man-unified-id-sr-03


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

     *   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 [e-mail]<mailto:[e-mail]> and ADs via [e-mail]<mailto:[e-mail]>.


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.