RE: Two questions on draft-ietf-ccamp-gmpls-ason-routing-ospf

[Igor Bryskin <i_bryskin@yahoo.com>]

Lyndon,

 

Let me try to explain my point.

 

Basically, we have two solutions to address the situation when the relationship between a router controller and data plane switches (TE nodes or TE routers) are 1:N, that is, when a single controller manages multiple TE routers.

 

Solution 1 (suggested in the draft):

 

Each TE Link advertising is extended with Local/Remote TE Router IDs pair. In this case, what is in the LinkID sub-TLV is not important really.

 

Solution 2 (mine)

 

The Router Address TLV is extended to advertise all TE Router IDs controlled by the advertising controller as routable addresses. The TE Link TLV is extended to advertise the local TE Router ID. However, there is no need to advertise the remote TE Router ID, because this is the function of the existing LinkID sub-TLV, which is to identify the remote end of the advertised TE link – remote TE Router ID.

 

Both these approaches solve the problem; however, an important question to answer is:

 

Do we need the TE Router IDs to be routable addresses?

 

The answer is YES according to draft-ietf-ccamp-gmpls-addressing-05.txt. For example, if the network
 is built of unnumbered TE links, than ERO signaled in RSVP-TE Path will contain
 path in a form of TE_RtrID/ifIndex pairs, and having TE_RtrID routable solves the problem how to signal the Path message along the provisioned path..

If you agree with this, than you will also agree that all TE Router IDs should be advertised within Router Address TLV

Hope that this helps.

Igor

 

"Ong, Lyndon" <Lyong@Ciena.com> wrote:

Hi Dimitri,

That was my understanding also, I don't see any issue with this.

Cheers,

Lyndon

-----Original Message-----
From: owner-ccamp@ops.ietf.org [mailto:owner-ccamp@ops.ietf.org] On Behalf Of Dimitri.Papadimitriou@alcatel-lucent.be
Sent: Friday, March 09, 2007 7:56 AM
To: Igor Bryskin
Cc: ccamp@ops.ietf.org; Brungard, Deborah A, ALABS; owner-ccamp@ops.ietf.org
Subject: Two questions on draft-ietf-ccamp-gmpls-ason-routing-ospf

igor

the drafts says

"Note: The Link ID sub-TLV that identifies the other end of the link (i.e.
Router ID of the neighbor for point-to-point links) MUST appear exactly once per Link TLV. This sub-TLV MUST be processed as defined in [RFC3630].
"

which is exactly what you are saying - when i say "it identifies the remote RC not the remote data plane "node" in case the remote RC is associate to n nodes" read "it is set to the router_id that identifies the remote RC..."
in brief, we keep the semantic and add a discriminator (that does not apply in case of colocated 1:1 LSR) - this closes the first point -

concerning the second point, since there is a possibility to have multiple associations in different LSAs i don't where the problem is ?

thanks,
-d.





Igor Bryskin
Sent by: owner-ccamp@ops.ietf.org
09/03/2007 16:05

To: Dimitri PAPADIMITRIOU/BE/ALCATEL@ALCATEL
cc: ccamp@ops.ietf.org, "Brungard, Deborah A, ALABS"

Subject: Re: Two questions on
draft-dimitri-ccamp-gmpls-ason-routing-ospf draft


Dimitri,

> Is the LinkID is the same as Remote TE Router ID?

no

> LinkID unambiguosly identifies remote data plane node,

no, it identifies the remote RC not the remote data plane "node" in case the remote RC is associate to n "nodes"

IB>> No, I disagree. You see that's why it's so important to quote the
RFCs/drafts, because people often interpret them differently.

In RFC 3630 we read:
"
2.5.2. Link ID



The Link ID sub-TLV identifies the other end of the link. For

point-to-point links, this is the Router ID of the neighbor.

"

Note that it does not say whether this is the advertising Router ID

(identifying neighbor RC) or TE Router ID (identifying the
neighbor TE node). However, it does say that it "identifies the other end
of the link". Because a link is terminated by TE nodes (and not
advertising routers) I conclude that LinkID identifies the remote TE node.

Furthermore, earlier in RFC 3630 we read:
"
2.4.1. Router Address TLV

The Router Address TLV specifies a stable IP address of the
advertising router that is always reachable if there is any
connectivity to it; this is typically implemented as a "loopback
address". The key attribute is that the address does not become
unusable if an
interface is down. In other protocols, this is known
as the "router ID"

I interpret that this is the same router ID as in the upper quote. It is
advertised in the Router Address TLV, which is the only way today to
advertise TE Router ID. Hence the router ID in the context of this RFC is
the TE Router ID.

The conclusion #1: the TE Link TLV, as it is today, always contains the ID
of the remote TE node.

The conclusion #2: there is a need to advertise several TE Router IDs
supported by the same RC (advertising router), which, I think, should be
proposed in your draft

ps: second question is trivial, mathematical vs networking formulation (no

real difference)

IB>> Well, it changes one of the fundamental definitions of G.8080, and I
am asking why is that in the draft which is supposed to define ways to
support G.8080

Igor

pps: if you want to put guidelines on e-mail responses probably directing
your e-mail to the GEN AREA would be more suitable

hope this helps,
-d.




Igor Bryskin
09/03/2007 00:03

To: Dimitri PAPADIMITRIOU/BE/ALCATEL@ALCATEL
cc: ccamp@ops.ietf.org, "Brungard, Deborah A, ALABS"

Subject: Re: Two questions on
draft-dimitri-ccamp-gmpls-ason-routing-ospf draft


Dimitri, no, it does not help.

You didn't answer the first question, which is:

Is the LinkID is the same as Remote TE Router ID? If no, what is the
difference? If yes, why do you need the latter? Both your pointers explain

why do you need advertising of the local TE Router ID (advertising router
may cover multiple data plane nodes), However, LinkID unambiguosly
identifies remote data plane node, and the need for the advertising of
Remote TE Router ID is not obvious

BTW, You didn't answer the second question either.

Igor

PS, I have a suggestion for the working group: Let us disallow responding
to the comments/questions by just pointing to RFCs or drafts. In my view
it is quite unfriendly. It is always possible to cut and paste a piece
from the relevant RFC or draft confirming the points the writer is trying
to make.

Dimitri.Papadimitriou@alcatel-lucent.be wrote:
igor


pls use version (or 03
when available to make comments)

in that version you will see in Section 5.2

" Note: The Link ID sub-TLV that identifies the other end of the link
(i.e. Router ID of the neighbor for point-to-point links) MUST
appear exactly once per Link TLV. This sub-TLV MUST be processed as
defined in [RFC3630]. "

now why this sub-TLV 17, well for the reason explained at the beginning of


par.5.2
but also in RFC 4652 Section 5.7

hope this helps,
-d.




Igor Bryskin
08/03/2007 22:11

To: Dimitri PAPADIMITRIOU/BE/ALCATEL@ALCATEL
cc: ccamp@ops.ietf.org, "Brungard, Deborah A, ALABS"

Subject: Two questions on
draft-dimitri-ccamp-gmpls-ason-routing-ospf draft


Dimitri,
I have a couple questions wrt the
draft-dimitri-ccamp-gmpls-ason-routing-ospf draft.
In 5.2 a TE Link sub-TLV is introduced for the purpose of advertising
local and remote TE Router ID:

0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 17 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local TE Router Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote TE Router Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Although I do understand why there is a need for advertising the Local TE
Router ID, I donââ'¬â"¢t understand why the Remote Te Router ID?
Isnââ'¬â"¢t
this is
the same
information
that is carried in the Link ID sub-TLV?
In 6. you write:

ââ'¬Å"A RA may contain smaller RAs inter-connected by links.
The limit of the subdivision results in
a RA that contains two sub-networks interconnected by a single
link.ââ'¬Â?

In G.8080 I read:
ââ'¬Å".... A routing area is defined by a set of subnetworks, the SNPP
links

that interconnect them, and the SNPPs representing the ends of the SNPP
links exiting that routing area. A routing area may contain smaller
routing areas interconnected by SNPP links. The limit of subdivision
results in a routing area that contains ]one subnetwork.ââ'¬Â?

Why is the discrepancy?

Thanks,
Igor


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