Subject: Doubt regarding the component links

From: mark Brown <[email-masked]>
Date: Fri, 28 Jan 2011 06:16:30 +0530

Hi,

Is it possible to create a composite link which has a physical
point-to-point link as one component link and an MPLS LSP as the other
component link?

Is it also possible to create a composite link that has two different
MPLS LSPs, both between the same endpoints, and each taking up a
different path, as the component links?

Thanks,
Mark

---

From: Tony Li <[email-masked]>
Date: Thu, 27 Jan 2011 16:55:53 -0800

> different path, as the component links?

I'm not quite sure of the context of your question.  In the context of draft-ietf-rtgwg-cl-requirement-03, it is quite clear:

      Composite Link:  A composite link is a logical link composed of a
           set of parallel point-to-point component links, where all
           links in the set share the same endpoints.  A composite link
           may itself be a component of another composite link, but only
           a strict hierarchy of links is allowed.

       Component Link:  A point-to-point physical or logical link that
           preserves ordering in the steady state.  A component link may
           have transient out of order events, but such events must not
           exceed the network's specific NPO.  Examples of a physical
           link are: Lambda, Ethernet PHY, and OTN.  Examples of a
           logical link are: MPLS LSP, Ethernet VLAN, and MPLS-TP LSP.

Both of the cases that you cite should be supported, per these requirements.

Tony

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From: mark Brown <[email-masked]>
Date: Fri, 28 Jan 2011 06:39:11 +0530

Hi Tony,

Thanks for the confirmation!

>> different path, as the component links?

Assume that i set up an MPLS LSP (or a pseudowire) between two points
and there lies a composite link in that path. When the traffic enters
the composite link it will get an MPLS label slapped on. Thus if the
original packet was carrying two MPLS labels (which usually happens
for L2 and L3 VPNs), it will now carry 3 labels, while its transiting
the composite link. Is my understanding correct here?

If this composite links terminates at an LER then it will have to pop
off at least two labels before it can process the packet. The first
label would correspond to the endpoint of the composite link and the
other for the original tunnel termination.

Thanks,
Mark

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From: Tony Li <[email-masked]>
Date: Thu, 27 Jan 2011 17:20:51 -0800

Hi Mark,

> the composite link. Is my understanding correct here?

Assuming the composite link has an LSP as a component, that seems not unreasonable.  However, might some implementations perform PHP?

Also, adding a third label is NOT necessary if the composite link is purely physical links.

> other for the original tunnel termination.

Sounds right.

Tony

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From: mark Brown <[email-masked]>
Date: Fri, 28 Jan 2011 07:13:59 +0530

Hi Tony,

> Also, adding a third label is NOT necessary if the composite link is purely physical links.

I agree. However, i was describing a case when my composite link
comprises of an MPLS LSP.

>> other for the original tunnel termination.

Thanks for the help

Mark

---

From: "Mcdysan, David E" <[email-masked]>
Date: Fri, 28 Jan 2011 09:51:11 -0500

Hi,

Some good discussion here, but I don't see a need to add or change
requirements text. 

May be good to capture some of these clarifications in the proposed
composite link framework document.

Thanks,

Dave

On 1/27/11 8:43 PM, "mark Brown" <[email-masked]> wrote:

>> Assuming the composite link has an LSP as a component, that seems not
>>unreasonable.  However, might some implementations perform PHP?
>>
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