Subject: questions of L2VPN

From: "zhangle" <[email-masked]>
Date: Sun, 24 Aug 2003 10:52:56 +0800

I have got the following drafts:
    draft-ietf-pwe3-control-protocol-03.txt,    draft-ietf-pwe3-ethernet-encap-03.txt
and draft-martini-l2circuit-trans-mpls-11.txt,  draft-martini-l2circuit-encap-mpls-05.txt

but the drafts seems to be conflicted.

when I create a L2VPN using LDP, May I change the L2 frame header on the ingress?
there is some describtion below:

in draft-martini-l2circuit-trans-mpls-11.txt,wrote:

3. Tunnel Labels and VC Labels 
   ...The transported frame MAY be modified when it reaches the egress router.
   If the header of the transported layer 2 frame is modified, this MUST
   be done at the egress LSR only.

but in draft-ietf-pwe3-control-protocol-03.txt:
5.4. Interface Parameters Field
...
- Requested VLAN ID.

       An Optional 16 bit value indicating the requested VLAN ID. This
       parameter MAY be used by an PE that is incapable of rewriting the
       802.1Q ethernet VLAN tag on output. If the ingress PE receives
       this request it MAY rewrite the VLAN ID tag in input to match the
       requested VLAN ID. If this is not possible, and the VLAN ID does
       not already match configured ingress VLAN ID the PW should not be
       enabled.This parameter is applicable only to PW type 4.

and in draft-ietf-pwe3-ethernet-encap-03.txt:
3.1.2. Raw Mode vs. Tagged Mode
...
If an ethernet PW is operating in raw mode, service-delimiting tags
   are NEVER sent over the PW.  If a service-delimiting tag is present
   when the frame is received from the CE by the PE, it MUST be stripped
   (by the NSP) from the frame before the frame is sent to the PW.

   If an ethernet PW is operating in tagged mode, every frame sent on
   the PW MUST have a service-delimiting VLAN tag.  If the frame as
   received by the PE from the CE does not have a service-delimiting
   VLAN tag, the PE must prepend the frame with a dummy VLAN tag before
   sending the frame on the PW.