contribution from ATM Forum

[Yakov Rekhter <[e-mail]>]

Folks,

Appended is a contribution from the ATM Forum that I volunteered to
carry over to the ROLC WG. The contribution describes how NHRP would be
used in the MPOA (multi-protocol over ATM) environment.

I'd like to point out essential differences between the current NHRP format
and what is proposed in the contribution:

1. Protocol ID (the NHRP packet format shows 2 octets, ATM Forum would like to
   see 6 octets).
2. ATM Forum would like to see support for variable length Source and 
   Destination addresses (via explicit Address Length field)
3. EDFG Origin Flag
4. There is a desire to have flags on a per next-hop entry 
   in the NHRP Reply (this is not shown in the appended contribution).

Please comment.

Yakov.
============================ cut here =========================================

Appendix A Resolution Message Contents vs. NHRP


TABLE 1. Resolution Request Contents

	NHRP 		Associated 	Comment(s)/Reason Added
	Field [3]	MPOA Field
	=================================================================
	Version		Version		P/O NHRP Fixed Header
	-----------------------------------------------------------------
	Hop Count	Hop Count	P/O NHRP Fixed Header
	-----------------------------------------------------------------
	Checksum	Checksum	Computed for the entire message -
					P/O NHRP Fixed Header
	-----------------------------------------------------------------
	Type		Message Type	P/O NHRP Fixed Header
	-----------------------------------------------------------------
	Mandatory Part	Mandatory Part 	P/O NHRP Fixed Header
	Length		Length		
	-----------------------------------------------------------------
	Q-Flag		Origin Type	Optional 
	-----------------------------------------------------------------
	S-Flag		Destination 	Clear in request
			Type
	-----------------------------------------------------------------
	A-Flag		Authority	Authoritative Indication - Always
					set for MPOA
	-----------------------------------------------------------------
	P-Flag		Status		Clear in request
	-----------------------------------------------------------------
	B-Flag		Stability 	Clear in request
	-----------------------------------------------------------------
			EDFG Origin	Uses unused NHRP bits (NHRP flags
					field) set if origin is an EDFG
	-----------------------------------------------------------------
	Protocol ID	Protocol ID	Based on ISO TR-9577:1990/3 -
					SNAP+ (total 6 bytes)
	-----------------------------------------------------------------
	Request ID	Transaction ID	Request/response match
	-----------------------------------------------------------------
			Address Length	Place holder for non-fixed length
					addresses
	-----------------------------------------------------------------
	Destination IP	Destination Inter-
	Address		network Address
	-----------------------------------------------------------------
			Address Length	Place holder for non-fixed length
					addresses
	-----------------------------------------------------------------
	Source IP	Origin Inter-
	Address		network Address
	-----------------------------------------------------------------
			List Length	zero in request	
	-----------------------------------------------------------------


TABLE 2. Resolution Response Contents

	NHRP 		Associated 	Comment(s)/Reason Added
	Field [3]	MPOA Field
	=================================================================
	Version		Version		Optional in MPOA resolution re-
					sponse - P/O NHRP Fixed Header
	-----------------------------------------------------------------
	Hop Count	Hop Count	P/O NHRP Fixed Header
	-----------------------------------------------------------------
	Checksum	Checksum	Computed for the entire message -
					P/O NHRP Fixed Header
	-----------------------------------------------------------------
	Type		Message Type	P/O NHRP Fixed Header
	-----------------------------------------------------------------
	Mandatory Part	Mandatory Part 	P/O NHRP Fixed Header
	Length		Length		
	-----------------------------------------------------------------
	Q-Flag		Origin Type	Copied from Request
	-----------------------------------------------------------------
	S-Flag		Destination 	Optional
			Type
	-----------------------------------------------------------------
	A-Flag		Authority	Authoritative Indication - Always
					set for MPOA
	-----------------------------------------------------------------
	P-Flag		Status		Non-zero value indicates failure
	-----------------------------------------------------------------
	B-Flag		Stability 	Mapping guarantee
	-----------------------------------------------------------------
			EDFG Origin	Uses unused NHRP bits (NHRP flags
					field) set if origin is an EDFG
	-----------------------------------------------------------------
	Protocol ID	Protocol ID	Based on ISO TR-9577:1990/3 -
					SNAP+ (total 6 bytes)
					MUST be the same as in request
	-----------------------------------------------------------------
	Request ID	Transaction ID	Copied from request
	-----------------------------------------------------------------
			Address Length	See corresponding request field
	-----------------------------------------------------------------
	Destination IP	Destination Inter-
	Address		network Address
	-----------------------------------------------------------------
			Address Length	See corresponding request field
	-----------------------------------------------------------------
	Source IP	Origin Inter-
	Address		network Address
	-----------------------------------------------------------------
			List Length	Number of MPOA Target entries in
					response
	-----------------------------------------------------------------
			MPOA Target	one or more MPOA target entries
	-----------------------------------------------------------------


TABLE 3. MPOA Target

	NHRP 		Associated 	Comment(s)
	Field [3]	MPOA Field
	=================================================================
	Next Hop IP	Next Hop Inter-	Internetwork Address of RSFG
	Address		network Address	local to the MPOA Target
	-----------------------------------------------------------------
	Source Holding	Source Holding	Useful un-refreshed lifetime of
	Time		Time		this Response
	-----------------------------------------------------------------
	Preference	Preference	Preference of this entry
					relative to other entries
	-----------------------------------------------------------------
	Address Type	ATM Address Type
	-----------------------------------------------------------------
	NBMA Length	ATM Address
			Length
	-----------------------------------------------------------------
	NBMA Address	Termination ATM
			Address
	-----------------------------------------------------------------
			AAL5 Max SDU	Optional
			size
	-----------------------------------------------------------------
			Destination 	Clear if destination is a host
			Type
	-----------------------------------------------------------------
			QoS Available	Optional
	-----------------------------------------------------------------