The MPLS WG Archive

[<Santanu.Ganguly@swisscom.com>]

Hi Luca,

Just a small observation which may or may not be relevant: If both links are connected to the same two routers via ethernet and are operating in raw mode, then its likely that the LDP Identifiers will be identical as you say. The first 4 octets will probably  be the router ID ( Loopback address in this case) and the Label Space ID, in accordance to RFC 3036, will be zero for per platform labels for ethernet. Hence 1 TCP connection.

Cheers

santanu

Santanu Ganguly
Swisscom Fixnet Wholesale AG
Binz-Ring 17
Zurich
Switzerland 

-----Original Message-----
From: Fantolino Luca [mailto:luca.fantolino@telecomitalia.it] 
Sent: Thursday, September 28, 2006 4:18 PM
To: Kishore Tiruveedhula
Cc: mpls@lists.ietf.org
Subject: RE: [mpls] Question regarding LDP session setup

Thanks for your reply.

I verified again the content of the LDP messages: both report the same LDP ID (the loopback address) and same Label Space ID (0).

In this case I understand you expect a single TCP connection be created.

bye
Luca

-----Original Message-----
From: Kishore Tiruveedhula [mailto:tiruveedhula@avici.com]
Sent: mercoledì 27 settembre 2006 18:42
To: Tempia Bonda Alberto; mpls@lists.ietf.org
Cc: Fantolino Luca
Subject: RE: [mpls] Question regarding LDP session setup

If the both links uses the same local LDP ID (LSR Id:label space id), then it should create single LDP session (single TCP connection).

I guess your case might be something like below:

If Router A (assuming passive) LDP ID on link1 is Ra:La1, on link2 is Ra:La2 and Router B (assuming Active) LDP ID on both links is same Rb:Lb.


Router A link1 (LDP ID is Ra:La1) <--> Router B link1 (LDP ID is Rb:Lb) Router A link2 (LDP ID is Ra:La2) <--> Router B link2 (LDP ID is Rb:Lb)


In this case, Router B opens two TCP connections and Router B accepts both connections, but it may be accepted the TCP connections
      link1 of Router A to link2 of Router B  and
      link2 of Router A to link1 of Router B.

In this case, the session initialization fails when it verifies the Initialization message with its Hello adjacency ( by using Receiver LDP Identifier in CommonSession Parameter TLV).


Thanks,
Kishore

-----Original Message-----
From: Tempia Bonda Alberto [mailto:alberto.tempiabonda@telecomitalia.it]
Sent: Wednesday, September 27, 2006 11:21 AM
To: mpls@lists.ietf.org
Cc: Fantolino Luca
Subject: [mpls] Question regarding LDP session setup


Hello,

I have a question about LDP session establishment between two LSRs connected by multiple links.
A problem has occurred in the network during LDP session set up between two routers linked by two Ethernet LANs. Below I describe the behavior.

 1. Router A sends a LDP HELLO message on each Ethernet link at the same time; the two messages are identical, including the router ID and the source IP address (IP address assigned to an internal interface).

 2. Router B tries to open two TCP connections with router A on port
646: it sends two TCP SYN packets (using two different local ports).

 3. Router A accepts both connections (TCP SYN ACK) and router B completes the TCP connections set up (TCP ACK): two TCP connections are now available for LDP message exchange.

 4. Router B (active role) sends two copies of the same LDP INITIALIZATION message to router A through the two TCP connections.

 5. Router A sends a LDP INITIALIZATION message on the first TCP connection and clears the second TCP connection (TCP FIN).

 6. Router A sends a LDP NOTIFICATION message with E-bit set and then resets the second TCP connection.

What happens is that two TCP connections are created and Router B tries to open two separate LDP sessions. It tries to open a second LDP session when the first one is not yet established with the result that router A closes both TCP connections and no LDP session is set up.

It is not clear to me whether this behavior is correct according to RFC 3036. In particular, is it correct that two TCP sessions are created and a router tries to open two LDP sessions (it sends two LDP INITIALIZATION
messages) with the same peer?

Thanks,
Alberto and Luca
--------------------------------------------------------------------

CONFIDENTIALITY NOTICE

This message and its attachments are addressed solely to the persons above and may contain confidential information. If you have received the message in error, be informed that any use of the content hereof is prohibited.
Please return it immediately to the sender and delete the message. Should you have any questions, please contact us by replying to webmaster@telecomitalia.it.

        Thank you

                                        www.telecomitalia.it

--------------------------------------------------------------------


_______________________________________________
mpls mailing list
mpls@lists.ietf.org
https://www1.ietf.org/mailman/listinfo/mpls


--------------------------------------------------------------------

CONFIDENTIALITY NOTICE

This message and its attachments are addressed solely to the persons above and may contain confidential information. If you have received the message in error, be informed that any use of the content hereof is prohibited. Please return it immediately to the sender and delete the message. Should you have any questions, please contact us by replying to webmaster@telecomitalia.it.

        Thank you

                                        www.telecomitalia.it

--------------------------------------------------------------------
                        

_______________________________________________
mpls mailing list
mpls@lists.ietf.org
https://www1.ietf.org/mailman/listinfo/mpls

_______________________________________________
mpls mailing list
mpls@lists.ietf.org
https://www1.ietf.org/mailman/listinfo/mpls