sr - spring - what's the deal with 2 names

aaron1 at aaron1 at
Thu Sep 10 22:32:45 UTC 2020

Thanks Jeff, this is pretty trippy… I mean the fact that VPNV4 L3VPN works over SRv6 !


I’m so accustomed to seeing L3VPN being an MPLS thing, and now, no labels, no mpls. Wow


The wireshark sniff shows…






That’s it.  No double mpls tags like I’ve so familiar with.


I wanted to look at the MP-iBGP update to see what was in there, but apparently this is so new, it seems that my wireshark decode doesn’t show everything.  I see “BGP Prefix-SID” and then an Unknown 37 bytes under that.  I wonder if I could enable the SR Wireshark decode.  I have had to do that for other protocols in the past.


   05 00 22 00 01 00 1e 00 fc 00 00 00 00 00 00 04

   00 00 00 00 00 00 00 00 00 ff ff 00 01 00 06 28

   18 10 00 10 40








From: Jeff Tantsura <jefftant.ietf at> 
Sent: Thursday, September 10, 2020 3:41 AM
To: aaron1 at
Cc: NANOG <nanog at>
Subject: Re: sr - spring - what's the deal with 2 names


SR could be instantiated with 2 data planes, MPLS and IPv6  - SR-MPLS and SRv6 respectively.

MPLS data  plane could be instantiated over either IPv4 or IPv6 (similarly to LDP6), MPLSoUDP->SRoUDP allows  transport of SR-MPLS over IP/UDP(RFC8663) and could be used to build innovative, end2end architectures, e.g.  draft-bookham-rtgwg-nfix-arch.
There is SFC related work, draft-ietf-spring-nsh-sr.

And there’s whole SRv6 thingy...

Let me know if I can help in any way.



On Sep 10, 2020, at 08:10, aaron1 at <mailto:aaron1 at>  wrote:

Interesting... I've never heard of SPRINGv4

I found it in the bottom section

I wonder if SPRINGv4 is like SRv6, meaning, SPRING(SR) over IPv4 dataplane?
Or, am I reading way too much into that SPRINGv4 acronym?


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