Why using MLDP if current LDP works and also support multicast

[Majed Saeed]

Hi , Just want to know in MPLS why I need to use MLDP to support multicast , however current LDP could achieve that along with multicast configuration  ?

Thank you

[Nagendra Kumar Nainar]

Hi Majeed,

LDP helps building unicast LSP. LDP by itself cannot support building multipoint (P2MP or MP2MP) LSPs. Traditionally in MPLS core, LDP is used to build unicast LSP while PIM is used to build multipoint trees with GRE as encapsulation. So unicast packets will be label switched while multicast packet will be IP forwarded with GRE encapsulation. This requires different control plane protocol and data plane encapsulation for unicast and multicast. 

mLDP is the extension to build the P2MP and MP2MP LSP. This helps with having one control plane protocol (LDP) and data plane encapsulation (label switching) for both unicast and multicast traffic.

HTH,

Nagendra

[Majed Saeed]

Thank you Nagendra . So does this mean if I configure command mpls mldp will make one control plane for both unicast & multicast packets ? Another thing suppose we have 10 PEs have run multicast VPN , how many GRE tunnel would be neighbouring ?

[Nagendra Kumar Nainar]

HI,

Please see below:

Thank you Nagendra . So does this mean if I configure command mpls mldp will make one control plane for both unicast & multicast packets ?

<Nagendra> By default, when "mpls ip" is enabled, it enables both LDP and mLDP. THe command "no mpls mldp" can be used to disable mLDP.

Another thing suppose we have 10 PEs have run multicast VPN , how many GRE tunnel would be neighbouring ?

<Nagendra>Each will have 1 GRE tunnel. With MVPN, the tunnel is mGRE and not P2P. So 1 mGRE tunnel is sufficient for any number of remote PEs.

-Nagendra