[Lsr] 答复: [spring] draft-ietf-isis-mpls-elc & draft-ietf-ospf-mpls-elc

["Aijun Wang" <[e-mail]>]

Hi, Les and Stephane:

 

https://tools.ietf.org/html/draft-wang-lsr-ospf-prefix-originator-ext-00 is
trying to solve what you are concerning for.

As you said, ELC/ERLD are functionally node capabilities, but when we try to
send traffic, we should consider the prefixes itself.

The above draft proposal to add prefix originator to address this. After
getting this information, the receiver can then build the relationship
between prefixes and ELC/ERLD.

 

 

Best Regards.

 

Aijun Wang

Network R&D and Operation Support Department

China Telecom Corporation Limited Beijing Research Institute,Beijing, China.

 

·¢¼þÈË: Les Ginsberg (ginsberg) [mailto:[e-mail]] 
·¢ËÍʱ¼ä: 2018Äê11ÔÂ20ÈÕ 2:00
ÊÕ¼þÈË: [e-mail]; [e-mail]
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Ö÷Ìâ: Re: [spring] draft-ietf-isis-mpls-elc & draft-ietf-ospf-mpls-elc

 

Stephane ¨C

 

The use case for this proposal is to support inter-AS scenarios in the
absence of a controller.

If the WG agrees that this use case needs to be addressed I believe the
proposal below is a good and viable compromise.

 

I say ¡°compromise¡± because ¨C as you mention below ¨C ELC/ELRD are
functionally node capabilities. But the inter-AS use case requires signaling
between AS¡¯s and the vehicle we have for doing that is a prefix
advertisement. The compromise is to advertise ELC associated with a prefix
¨C but not do so for ERLD.

This seems reasonable to me.

 

One change to what you state below ¨C I think ¡°when a prefix is leaked or
redistributed, the ELC associated to the prefix MUST also be
leaked/redistributed.¡±.

 

   Les

 

 

From: Lsr <[e-mail]> On Behalf Of [e-mail]
Sent: Friday, November 09, 2018 6:30 AM
To: [e-mail]
Cc: [e-mail]
Subject: [Lsr] draft-ietf-isis-mpls-elc & draft-ietf-ospf-mpls-elc

 

Hi WG,

 

Some discussions occurred on the mailing list on how to encode the entropy
label capability for SR but we hadn¡¯t found a consensus on the target
solution.

IETF 103 was the opportunity to meet face to face various people that have
participated to this discussion.

 

Following this discussion, we are coming with the following proposal that
the WG need to validate:

 

The entropy label capability is still considered as a per node property (for
simplicity reason, we do not want to have an ELC per linecard).

The ERLD is considered as a per node property (for simplicity reason, we do
not want to have an ERLD per linecard).

 

However IGPs may advertise prefixes that are not belonging to the node
itself in addition to the local prefixes of the nodes.

A typical use case is when two IGP domains (running the same protocol or a
different one) are redistributing routes between each other.

The inter-area use case is also creating a similar situation.

 

When an ingress node pushes an entropy label below a segment  it must ensure
that the tail-end of the segment is entropy label capable otherwise packets
will be dropped.

 

As a consequence, when prefixes are redistributed, the entropy label
capability of the node who has firstly originated the prefix, should be
associated to the prefix during the redistribution.

 

In terms of encoding, we propose to associate an entropy label capability
for each prefix advertised by a node.

The entropy label capability will be encoded as part of the Prefix
Attributes IGP extension (RFC7794 and RFC7684).

The entropy label capability may be set for local prefixes (e.g. loopbacks)
by a local configuration and for leaked/redistributed prefixes. When a
prefix is leaked or redistributed, the ELC associated to the prefix may be
also leaked/redistributed.

 

An ingress should set the entropy label below a Node/Prefix segment only if
the prefix associated to the Node/Prefix segment as the ELC set in the
Prefix Attributes.

An ingress should set the entropy label below an Adjacency segment only if
the adjacent neighbor of the node that has advertised the Adj SID is
advertising an ERLD (and so is entropy label capable).

 

For the binding SID, as IGPs are not involved in the signaling of the
binding SID, there is nothing to do in these drafts. 

 

 

Let us know your comments/feedback on this proposal so we can progress these
documents.

 

Brgds,

 

Stephane

 

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