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[OSPF] Re: RFC3630 - Local and Remote Interface IP address

Hi Vijay,

OSPF-TE implementers may wish to disagree with me on this, but I think Dimitri's definitive statement does not cover the basic reasoning for this feature.

While it is true that one can use multiple link addresses to identify multiple component links, I think that the multiplicity of link addresses is provided in this RFC so that a single TE link may support multiple interfaces. This is an implementation choice, and may be advantageous in some cases.

If the multiple link addresses are used to identify multiple component links, then I would expect a 1:1 correspondence between the link ends. If the addresses are used to identify different interfaces to the same link then I would not necessarily expect a 1:1 correspondence.

In answer to your most recent questions:

Section 2.4.2 of rfc3630 says: "The Link TLV describes a single link."

And so it does.
It describes a single TE link.
A link bundle is still a single TE link, but it is made up of multiple component links that are not identified as TE links in their own right.

Section 2.5.3 of rfc3630 says: "The Local Interface IP Address sub-TLV
specifies the IP address(es) of the interface corresponding to this link."

Section 2.5.4 of rfc3630 says: "The Remote Interface IP Address sub-TLV
specifies the IP address(es) of the neighbor's interface corresponding to
this link."


As above

Doesn't this mean the Local and Remote Interface IP Address sub-TLV
corresponds to just ONE TE-Link?


Yes, it does.

There is no mention of "components" anywhere in this document. Even in
rfc4201, it is not clear that when multiple (component) TE-Links are
aggregated as a single numbered bundled link, there can be more than one
Interface IP address used for Local and Remote Interface IP Address.

Could you please provide a reference where this is clarified as the mean for
advertising multiple components at once.

I don't think you will find such a reference.
What is clear is that an implementation MAY assign multiple interface IP addresses.
Therefore, there is nothing to stop an implementation using the component link identifiers as the set of interface IP addresses.
Since each component link is in just one bundle, the use of a component link identifier uniquely identifies the bundle.
This mechanism of advertising is, therefore, a clever way of advertising bundle membership information to the neighbor.

If you want a more definitive statement of how this can work, you should probably develop an Applicability Statement I-D.

Regards,
Adrian

Thanks and best regards,

Vijay


-----Original Message-----
From: Dimitri.Papadimitriou at alcatel.be
[mailto:Dimitri.Papadimitriou at alcatel.be]
Sent: Thursday, July 06, 2006 1:57 AM
To: Pandian, Vijay
Subject: Re: RFC3630 - Local and Remote Interface IP address


hi vijay - this was meant for advertizing multiple components at once




"Pandian, Vijay" <Vijay.Pandian at sycamorenet.com>
Sent by: owner-ccamp at ops.ietf.org
06/07/2006 02:56

       To:     ospf at ietf.org
       cc:     mpls at ietf.org, ccamp at ops.ietf.org
       Subject:        RFC3630 - Local and Remote Interface IP address


Section 2.5.3 indicates that there can be more than one Local Interface IP
address assigned to a (numbered) TE-Link. Similarly, section 2.5.4
indicates that there can be more than one Remote Interface IP Address
assigned to a (numbered) TE-Link.

Is there any requirement that the number of Local Interface IP address
assigned to a given TE-link match the number of Remote Interface IP
address.

Specifically, can a TE-Link have just one Local Interface IP address but
multiple Remote Interface IP Address or vice-versa?

Best regards,

Vijay







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