Subject: LLC/SNAP encapsulation over ATM interface for control connection

From: "Igor Achkinazi" <[email-masked]>
Date: Wed, 22 Aug 2001 15:27:03

Hi,

Could somebody, please, clarify LLC/SNAP encapsulation issue for non-MPLS 
connection between peers connected via ATM interface? (Rfc3035, MPLS over 
ATM, section "7. Use of VPI/VCIs")
Such connection must use LLC/SNAP encapsulation. Is this connection used for 
unlabeled traffic only? Can this connection carry MPLS labeled packets in 
case PHP and original packet has more than one label on stack? Can LSR send 
labeled packet over this control connection without PHP in case two peers 
are BGP speakers with VPN capability (two labels on label stack – bottom 
label is BGP/VPN label, possibly missing top label is for tunnel between BGP 
speakers).

Thank you,
Igor

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From: Kapil Vuthoo <[email-masked]>
Date: Thu, 23 Aug 2001 01:26:37 +0530

hi , 

to carry multiple protocols on an atm connection one has to use either LLC/SNAP 
encapsulation or VC multiplexing. It is specified in sec 7 RFC 3035 that all labeled packets MUST use VC multiplexing, ragardless of the encoding technique u r using(SVC, SVP or SVP multipoint encoding).
Further, the non -MPLS connection which is being talked about in RFC3035 sec7,
is the connection which must be there for ldp peers to communicate. This connection uses LLC/SNAP encap. & this connection may be used for other unlabeled packets also.
PHP is not possible in ATM as the label has to go in the vpi/vci field.  
ihope i am clear
  \kapil

On Wed, 22 Aug 2001 15:27:03