Subject: customer BPDU ethernet encapsulation over rfc1483(2684) ATM PVCs.

From: narasimhan g <[email-masked]>
Date: Thu, 4 Aug 2005 14:49:04 -0700 (PDT)

Hi,

I have a question regarding customer BPDU encapsulation over ATM PVCs.

The VPLS draft draft-ietf-l2vpn-vpls-ldp-07.txt seems to suggest that the
all frames that traverse a VPLS will have ethernet encasulation ( see below for quotes
from the draft).  Does it mean that customer BPDUs received over an rfc1483/2684 ATM PVC
will/must also have an ethernet encasulation?  RFC1483 encapsulation of BPDUs suggests
otherwise. Can someone please clarify.

Attached below is relevant text from sections 7.1 and 4.4.

thanks,

narasim

7.1. VPLS Encapsulation actions 

<snip>

 By following the above rules, the Ethernet frame that traverses a   <==============
  VPLS is always a customer Ethernet frame.  Note that the two 
  actions, at ingress and egress, of dealing with service delimiters 
  are local actions that neither PE has to signal to the other.  They 
  allow, for example, a mix-and-match of VLAN tagged and untagged 
  services at either end, and do not carry across a VPLS a VLAN tag 
  that has local significance only.  The service delimiter may be an 
  MPLS label also, whereby an Ethernet PW given by [PWE3-ETHERNET] 
  can serve as the access side connection into a PE.  An RFC1483 
  Bridged PVC encapsulation could also serve as a service delimiter.  
  By limiting the scope of locally significant encapsulations to the 
  edge, hierarchical VPLS models can be developed that provide the 
  capability to network-engineer scalable VPLS deployments, as 
  described below. 

4.4. Loop free VPLS 
   
  If the topology of the VPLS is not restricted to a full mesh, then 
  it may be that for two PEs not directly connected via PWs, they 
  would have to use an intermediary PE to relay packets.  This 
  topology would require the use of some loop-breaking protocol, like 
  a spanning tree protocol. 
   
  Instead, a full mesh of PWs is established between PEs.  Since 
  every PE is now directly connected to every other PE in the VPLS 
  via a PW, there is no longer any need to relay packets, and we can 
  instantiate a simpler loop-breaking rule - the "split horizon" 
  rule: a PE MUST NOT forward traffic from one PW to another in the 
  same VPLS mesh. 
   
  Note that customers are allowed to run the Spanning Tree Protocol 
  (STP) such as when a customer has "back door" links used to provide 
  redundancy in the case of a failure within the VPLS.  In such a     <==============
  case, STP Bridge PDUs (BPDUs) are simply tunneled through the 
  provider cloud. 

____________________________________________________
Start your day with Yahoo! - make it your home page 
http://www.yahoo.com/r/hs