Re: [mpls] [bess] draft-rosen-mpls-rfc3107bis

Robert Raszuk <> Fri, 01 April 2016 20:23 UTC

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Date: Fri, 01 Apr 2016 22:23:41 +0200
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From: Robert Raszuk <>
To: Eric C Rosen <>
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Subject: Re: [mpls] [bess] draft-rosen-mpls-rfc3107bis
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Hi Eric,

I have read your proposed draft as well as watched this thread with a bit
of an interest.

To me the best compromise - which is to agree with Bruno's points as well
as address your intentions is simply to request new SAFI for 3107bis.

>From the draft you are really not updating 3107 base spec but obsoleting it
which to me looks like a bad idea.

You are even requesting to remove IANA reference to original spec. How
would IANA know when is it safe to do that .. meaning when all
implementations will not suddenly support and all deployments will enable
3107bis ?

New SAFI requires a new capability which you are asking for anyway.

As far as implementations please keep in mind very important point that
some implementations treat SAFI 1 & 4 in single table and some in separate
tables. That when mixed with 3107bis may just explode if not in new set of
bugs then with operational nightmare. While we are at this it would be much
cleaner to mandate in the new spec to have 3107bis always to use separate
tables as compared with from SAFI 1.



As we all know 3107(bis) tries to add NNI to MPLS. However it must be very
well stated that this is only one deployment option for interdomain
encapsulation. I would very much like to see a section indicating that IPv6
or/and IPv4 be used as an alternative encap for those applications which
require it and when needed provide local bindings between intradomain MPLS
and interdomain IP.

On Fri, Apr 1, 2016 at 6:44 PM, Eric C Rosen <> wrote:

> On 3/25/2016 7:25 AM, wrote:
>> I'm quite sure you have deployed  implementations, from several
>>> prominent vendors, that will not properly handle this case.
>> I'm waiting for this/these implementation(s) to make a public statement
>> in this thread / IETF WGs. Then we can discuss whether the issue comes from
>> RFCF3107 or from the implementation.
>> If none make a public statement, we should assume that all
>> implementations are capable of receiving multiple labels, as per RFC 3107.
> I strongly disagree with this.  We should not ignore the facts just
> because you don't like the way the facts were gathered.
> A better approach would be to have operators state whether they have any
> deployments in which the "multiple labels" feature is used in a
> multi-vendor environment.  It is very useful when working on a "bis" draft
> to determine which features have been proven to work in a multi-vendor
> environment and which have not.
> Any non-compliant implementation may create interoperability issues and
>> unpredictable results.
>>  From an IETF standpoint, the question is whether a RFC 3107
>> implementation would create interoperability issues, up to shutting down
>> the BGP session.
> There are deployed 3107 implementations which always assume that the NLRI
> contains a single label.  If you tried to interwork these with 3107
> implementations that send multiple labels , you will experience the kind of
> disruption.  3107bis tries to allow the use of multiple labels while
> preventing this sort of disruption from occurring.
> If you mean that some non-compliant implementation do not work, well let's
>> fix them.
> The situation is that there is a commonly deployed "bug" in old
> implementations, but it is not seen because the bug is in a feature that no
> one has been using.  If new implementations use that feature, the bug will
> be seen, and network disruption will occur. One could say "fix all the old
> implementations", but it seems wiser to have new implementations avoid
> tickling the bug.   The Capability is not proposed  for the purpose of
> helping the vendors, it's there to help the operators.
> I'm not sure why you think there would be BGP session drops due to
> 3107bis; if a 3107 implementation sends multiple labels to a 3107bis
> implementation, I think the 3107bis implementation would do
> "treat-as-withdraw" rather than "drop the session".
> Perhaps a reasonable approach for 3107bis would be the following:
> - A 3107bis implementation will not send multiple labels to a peer unless
> the Capability has been received from that peer.  (This prevents 3107bis
> implementations from tickling the 'bug' in 3107 implementations.)
> - A 3107bis implementation will accept multiple labels from a peer even in
> the absence of the Capability.
> Another approach would be to have a knob that determines whether the
> Capability needs to be used before multiple labels are advertised.
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