Re: [spring] packet captures for draft-ietf-spring-srv6-network-programming-06?

["Darren Dukes (ddukes)" <[e-mail]>]

Hi Andrew,

You state that “code seems to be *way* off the draft”, but there is nothing in your email to support this.
You have made claims based on unfortunate misunderstandings of SRv6.

For example, your understanding of End.X SID is not correct.
You appear to be confusing SRv6 SID Function and an SRv6 Segment Behavior.
These are clearly defined in section 2 of draft-ietf-spring-srv6-network-programming and described in detail later in the draft.
Allow me to explain:
- Several End.X SIDs are instantiated in the same router, one “adjacency SID” per adjacency seems about right.
- Each SID will be unique, i.e. a unique IPv6 address.
- The address does not encode the SRv6 Segment Behavior codepoint (e.g. 0x0006). These Behavior codepoints (as captured in “Table 4: IETF - SRv6 Endpoint Behaviors)  are for control plane use.

Let’s return focus to discussing technical points and progressing the WG agenda and milestones with diligence and a constructive mindset.

Thanks
  Darren

On Dec 17, 2019, at 12:57 AM, Andrew Alston <[e-mail]<mailto:[e-mail]>> wrote:

Alex,

Will try and get you some captures off the devices I’ve been testing on – in order to make sure I understood this draft properly, and in light of the deployment status draft, I decided to play a lot more deeply and setup a bit of a lab.  I’m still doing tests and soon as I have some other bits completed will send through the packet captures from those against (Since the XR boxes that I have to test on seem to have absolutely no ability to setup traffic steering with SRv6 (and I actually have requested details of how to configure this in the past but gotten no response), I’m just finishing the code to inject packets from outside with a sid stack to test this.  I also acknowledge that I’m running tests against code that is implementing a draft that seems far from final – and so shouldn’t have that many expectations.

That being said, In light of the deployment draft – I do have some concerns that there is a draft that specifies that people have put this stuff into production – yet the implementation in current shipping code seems to be *way* off the draft and contrary to things we have been told in the working group.

Some of the more interesting finds so far:


  *   In Montreal – I questioned the growth in the IGP tables – since I would have to use a separate locator on each router – I was explicitly told this wasn’t necessary and could use the loopbacks – not so in current code – use of the loopback marks the locator as down.



  *   Locator size is not configurable as anything other than a /64



  *   XR 7.0.1 claims a maximum number of SID’s at 8000 – I’m still unclear if this limitation in the code is based on locally configured SID’s or received SID’s – and will run some tests on this in the coming day or two to verify



  *   There seems to be a limit on a single locator per box – I’m still trying to figure out what impact this will have in a multi-area or multi-level IGP deployment scenario.



  *   By default when configuring a locator – the device configures a separate End.X (PSP) for each interface – now – this is where things get interesting.  If I am reading the NP text correctly, End.X (PSP) should be locator:0006::  - However, in the shipping code, that is not the case at all – as per the below:


RP/0/RP0/CPU0:SRV6-R2#show segment-routing srv6 locator R2 sid Sun Dec 15 04:56:10.913 UTC
SID                         Behavior     Context                           Owner               State  RW
--------------------------  -----------  ------------------------------    ------------------  -----  --
2001:db8:ee:2:1::           End (PSP)    'default':1                       sidmgr              InUse  Y
2001:db8:ee:2:11::          End.OP       'default'                         sidmgr              InUse  Y
2001:db8:ee:2:40::          End.X (PSP)  [Gi0/0/0/0, Link-Local]           isis-64             InUse  Y
2001:db8:ee:2:41::          End.X (PSP)  [Gi0/0/0/1, Link-Local]           isis-64             InUse  Y
2001:db8:ee:2:42::          End.X (PSP)  [Gi0/0/0/3, Link-Local]           isis-64             InUse  Y

So from my perspective – I have to wonder about the production deployments – because particularly on this last point – if people have been putting this stuff in production, and the implementation is so different from the text, its going to create some rather interesting breakage going forward if my reading of the text is correct.

Anyway – will send some packet captures hopefully in the next 48 hours once I’ve got a more complete set of captures from my lab setup.

Thanks

Andrew


From: spring <[e-mail]<mailto:[e-mail]>> On Behalf Of Alexandre Petrescu
Sent: Monday, 16 December 2019 17:34
To: SPRING WG email list <[e-mail]<mailto:[e-mail]>>
Subject: [spring] packet captures for draft-ietf-spring-srv6-network-programming-06?

Hi, SPRINGers,

My comments on SRv6 relate to a worry about modifying packets in transit.

In order to better explain myself, or maybe to remove the worry
altogether, I would like to ask for packet dumps of SRv6.

By looking at the packet contents that go into the network it is much
easier to clarify and to avoid misunderstandings.

Alex

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