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New Member

MPLS

Hi,

Could anyone say why we use MPLS in multicast mode?

It could be protection. But outside protection, are there other reasons?

Thanks for your words.

Best regards,

Michelot

6 REPLIES
Hall of Fame Super Silver

Re: MPLS

Hello Michelot,

may you explain what do you mean for MPLS in multicast mode?

LDP discovery process uses UDP packets with 224.0.0.2 multicast destinations on port 646, but then TCP unicast sessions are built between discovered adjacent nodes, using well known port 646 on one side and LDP router-ids as source and destination addresses.

Hope to help

Giuseppe

New Member

Re: MPLS

Hello Giuslar,

> may you explain what do you mean for MPLS in multicast mode?

I mean p2mp. But perhaps it's again not really sufficient because we have to consider if we have :

(1) MPLS used in an oriented connection network,

(2) MPLS used in an connectionless network.

In the case (1) p2mp is like broadcast, and the same information is transmit over several paths. We have a sub-set of MPLS, typically oriented connection, nammed before T-MPLS (promoted by ITU-T), and now MPLS-TP (promoted by IETF, with the ITU-T agreement).

Tha case (2) also exists or has also existed. In this case p2mp is not simply broadcast. For example, I heard about the ECMP mechanism in IP/MPLS which is typically connectionless. The order of the information transmitted is not kept, and we can add a sequence number.

> LDP discovery process uses UDP packets with 224.0.0.2 multicast destinations on port 646...

Thanks for this description.

Best regards,

Michelot

Hall of Fame Super Silver

Re: MPLS

Hello Michelot,

excuse me for explaining what you already know!

I remembered you had already posted about MPLS so I thought:

or he'asking about a new advanced topic I don't know (as indeed you have done) or it is a question about LDP on a LAN.

You got the correct answer from Harold Ritter.

Best Regards

Giuseppe

New Member

Re: MPLS

Hello Giuseppe,

> excuse me for explaining what you already know!

Your reply was really interresting and pertinent.

Perhaps I'm sometimes a little bit advanced, but also too often late.

- Giving more details helps me to clarify my thought,

- I always need to understand better what I think to understand (...and it's better talking with you for these subjects than with my wife);

- We don't write for us. Anybody can read and has also the right to understand.

Best regards,

Michelot

Cisco Employee

Re: MPLS

Michelot,

If you mean point to multipoint (p2mp) traffic engineering tunnels, then the answer is that they are used for protection but also to dictate the path the multicast traffic will take in the SP core. The p2mp tunnels are mostly used for video transport.

Regards

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
New Member

Re: MPLS

Hello Hritter,

> If you mean point to multipoint (p2mp) traffic engineering tunnels...

You can see my added comments above.

> ... The p2mp tunnels are mostly used for video transport.

Thanks for these words.

Best regards,

Michelot

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