Subject: Request for one more clarification on IP with MPLS

From: "Relan, Sandeep" <[email-masked]>
Date: Sun, 12 Nov 2000 23:47:40 -0800

Dear John Runham, Ramanjaneyulu and Seenu,

 Thank you to all of you for the prompt and detailed 
 clarifications.!!

 Now, I have come across another basic doubt.
 I noticed that the mpls draft :
   
    draft-ietf-mpls-label-encaps-08.txt
 
 does not  address the Ethernet - IP type field
 presence after MPLS labels :

  |---------------------------------|
  | L2  | MPLS   | IP Header	      |  	
  |---------------------------------|

  In standard Ethernet-II or 802.3 LLC/SNAP (non-MPLS) 
  switching / routing, the Type field "0x800" comes after
  the L2 header, which indicates that it is an IP packet. 

  But, in case of MPLS switched packets :

  Q1.  Will the IP header after the MPLS, contain 2 bytes 
       of Type field (0x800) in the begining of IP Header...??

                 or

  Q2. For MPLS packets, Is IP the implicit protocol supported ..??
      Thereby no type field is required after the MPLS labels and
      the bytes after MPLS labels  "MUST" be the IP Header without
      type field  !! 

 Thanking you all for your kind help.

 - Sandeep

---

From: "Peter Tam" <[email-masked]>
Date: Mon, 13 Nov 2000 15:37:39 -0600

Hi, Sandeep:

Not sure which 2 bytes of TYPE field in the IP header you meant? But,
basically, the Ethernet frame header has assigned Ethertype values to
indicate that it is encapsulating MPLS unicast data frames or multicast data
frames. The last MPLS label in the label stack would have an Explicit NULL
label (with the end of Stack bit set) to indicate it is dealing with IPv4 or
IPv6. Or you may use administration (MPLS signaling may achieve likewise) to
allocate certain label space to indicate it is dealing with IP or others.
Implicitly, it defaults to all IP.

Regards...Peter Tam,
Nortel Networks.

	-----Original Message-----
	From:	Relan, Sandeep [SMTP:[email-masked]]
	Sent:	Monday, November 13, 2000 2:48 AM
	To:	[email-masked]'; [email-masked]';
[email-masked]'
	Cc:	[email-masked]'
	Subject:	Request for one more clarification on IP with MPLS

	   

	                 or

	 - Sandeep