VPLS again...

[nisha_kulkarni]

Hi Friends...

Please refer the file attached herein...

Please refer the very first page which talks of VPLS config between PEs.

As observed from the configs, under every VFIs, neighbor PEs have been configured...Now my question is that when we talk of VPLS, it's purely layer 2 technology. Then why are we using the IP addresses of the PE's in order to peer with each other over here???Isn't LAYER3 aspect coming into picture over here in this particular attachment when the author is talking about VPLS????

Kindly please answer my query since this is increasing the boundary of my doubts...

Regards,

NISHA

[Harold Ritter]

You are correct when you say that VPLS is layer 2 technology. The layer 2 frames received fom the ingress interface are encapsulated in MPLS in order to get from the ingress to the egress PE. On the egress PE, the MPLS encapsulation is removed and the layer frame is forwarded on the egress interface.

The label that is used forward the layer2 frames from the ingress to egress PE is selected based on the IP address specified on the VPLS configuration.

Hope this helps,

[nisha_kulkarni]

HI.....

Agreed that the layer 2 frames recived from the ingress interface are encapsulated in MPLS domain...But My worry is when u say a layer 2 approach, it should be a complete layer 2 connectivity...Can't u have any layer 2 technologies (say like VLAN) instead of IP addressing between the PEs????I mean to say can't the PEs have peering based on layer 2 instead of layer 3????

Regards,

NISHA

[adityakaul]

Nisha,

As Harold specified,

You have to first specify the PE's(Site) which will be part of the VPLS instance.

This will enable the Pseudowires to the respective PE's and signal a T-LDP session for the VC label exchange.

This ldp session(Tcp) will require a Transport address....which requires a L3 address.

This is as far as control plane signalling of the VC labels is concerned.

As far as Data plane is concerned when the l2 frames arrive at ingress i/f there is an imposition of 2 labels...ie VC label which is used to define the egress interface on the Egress PE and Igp label which is used to forward the packet till the Egree PE(PW-Tailend.

VPLS is a layer 2 technology riding on a l3 MPLS Network.

Pls refer the below mentioned draft's for a better understanding of the same.

Hope this helps.

Regards,

Aditya

http://www.ietf.org/internet-drafts/draft-ietf-pwe3-control-protocol-16.txt

http://www.ietf.org/internet-drafts/draft-ietf-l2vpn-vpls-ldp-06.txt

[nrajanpanda]

Agree with Aditya. Mail me your mobile no. I lost it.

[Harold Ritter]

In the example provided, the PEs are directly connected, which is not the case in most customer networks. Imagine the scalability issues trying to create a full mesh of L2 connectivity between potentially hundreds of PEs that are several hops away. It makes more sense to use a common infrastructure that is used not only by l2vpn but a myriad of other services. This is precisely why MPLS is used to encapsulate the L2 traffic going through the core.

Hope this helps,

[nisha_kulkarni]

Hi Mr.Harold and Aditya...

Thanks for the info.That was pretty useful link and information