< draft-ietf-ospf-manet-single-hop-mdr-03.txt		draft-ietf-ospf-manet-single-hop-mdr-04.txt >
	Network Working Group R. Ogier		Network Working Group R. Ogier
	Internet-Draft SRI International		Internet-Draft SRI International
	Updates: 5614 June 3, 2013		Updates: 5614 August 7, 2013
	Intended status: Experimental		Intended status: Experimental
	Expires: December 5, 2013		Expires: February 8, 2014
	Use of OSPF-MDR in Single-Hop Broadcast Networks		Use of OSPF-MDR in Single-Hop Broadcast Networks
	draft-ietf-ospf-manet-single-hop-mdr-03.txt		draft-ietf-ospf-manet-single-hop-mdr-04.txt
	Abstract		Abstract
	RFC 5614 (OSPF-MDR) extends OSPF to support mobile ad hoc networks		RFC 5614 (OSPF-MDR) extends OSPF to support mobile ad hoc networks
	(MANETs) by specifying its operation on the new OSPF interface of type		(MANETs) by specifying its operation on the new OSPF interface of type
	MANET. This document describes the use of OSPF-MDR in a single-hop		MANET. This document describes the use of OSPF-MDR in a single-hop
	broadcast network, which is a special case of a MANET in which each		broadcast network, which is a special case of a MANET in which each
	router is a (one-hop) neighbor of each other router. Unlike an OSPF		router is a (one-hop) neighbor of each other router. Unlike an OSPF
	broadcast interface, such an interface can have a different cost		broadcast interface, such an interface can have a different cost
	associated with each neighbor. The document includes configuration		associated with each neighbor. The document includes configuration
	skipping to change at page 2, line 51 ¶		skipping to change at page 2, line 51 ¶
	o In addition to full-topology LSAs, partial-topology LSAs may be		o In addition to full-topology LSAs, partial-topology LSAs may be
	used to reduce the size of router-LSAs. Such LSAs are formatted		used to reduce the size of router-LSAs. Such LSAs are formatted
	as standard LSAs, but advertise links to only a subset of		as standard LSAs, but advertise links to only a subset of
	neighbors.		neighbors.
	o Optionally, differential Hellos can be used, which reduce		o Optionally, differential Hellos can be used, which reduce
	overhead by reporting only changes in neighbor states.		overhead by reporting only changes in neighbor states.
	This document describes the use of OSPF-MDR in a single-hop broadcast		This document describes the use of OSPF-MDR in a single-hop broadcast
	network, which is a special case of a MANET in which each router is a		network, which is a special case of a MANET in which each router is a
	(one-hop) neighbor of each other router. Unlike an OSPF broadcast		(one-hop) neighbor of each other router. An understanding of
	interface, such an interface can have a different cost associated		[RFC5614] is assumed. Unlike an OSPF broadcast interface, such an
	with each neighbor. An example use case is when the underlying radio		interface can have a different cost associated with each neighbor.
	system performs layer-2 routing, but has a different number of		An example use case is when the underlying radio system performs
	(layer-2) hops to (layer-3) neighbors.		layer-2 routing, but has a different number of (layer-2) hops to
			(layer-3) neighbors.
	The rationale for using this interface type for single-hop broadcast		The rationale for using this interface type for single-hop broadcast
	networks, instead of a broadcast interface type, is to represent the		networks, instead of a broadcast interface type, is to represent the
	underlying network in a point-to-multipoint manner, allowing each		underlying network in a point-to-multipoint manner, allowing each
	router to advertise different costs to different neighbors in its		router to advertise different costs to different neighbors in its
	router-LSA. In this sense, this document shows how the OSPF-MDR		router-LSA. In this sense, this document shows how the OSPF-MDR
	interface type can be configured (and simplified if desired) to		interface type can be configured (and simplified if desired) to
	achieve the same goals as the OSPF Hybrid Broadcast and Point-to-		achieve the same goals as the OSPF Hybrid Broadcast and Point-to-
	Multipoint interface type [RFC6845].		Multipoint interface type [RFC6845].
	skipping to change at page 3, line 37 ¶		skipping to change at page 3, line 38 ¶
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	2. Operation in a Single-Hop Broadcast Network		2. Operation in a Single-Hop Broadcast Network
	When OSPF-MDR is used in a single-hop broadcast network, the		When OSPF-MDR is used in a single-hop broadcast network, the
	following parameter settings and options (defined in [RFC5614])		following parameter settings and options (defined in [RFC5614])
	should be used:		should be used:
	o AdjConnectivity SHOULD be equal to 2 (biconnected), MAY be equal		o AdjConnectivity SHOULD be equal to 2 (biconnected); this provides
	to 1 (uniconnected), and SHOULD NOT be equal to 0 (full topology).		the smoothest transition when one router replaces another as MDR,
			since the set of adjacencies forms a biconnected network which
			remains connected during the transition.
			o AdjConnectivity MAY be equal to 1 (uniconnected), resulting in a
			slightly less smooth transition since adjacencies must be formed
			between the new MDR and all of its neighbors.
			o AdjConnectivity SHOULD NOT be equal to 0 (full topology) since
			this requires adjacencies to be formed between all pairs of
			routers, adding unnecessary message overhead.
	o An adjacency SHOULD be eliminated if neither the router nor		o An adjacency SHOULD be eliminated if neither the router nor
	the neighbor is an MDR or BMDR (see Section 7.3 of [RFC5614]).		the neighbor is an MDR or BMDR (see Section 7.3 of [RFC5614]).
	o LSAFullness MUST be equal to 4 or 5 if full-topology LSAs are		o LSAFullness MUST be equal to 4 or 5 if full-topology LSAs are
	required. (The value 5 is defined in Section 3 of this document.)		required. (The value 5 is defined in Section 3 of this document.)
	o LSAFullness MAY be equal to 1 (min-cost LSAs) if full-topology		o LSAFullness MAY be equal to 1 (min-cost LSAs) if full-topology
	LSAs are not required. This option reduces the number of		LSAs are not required. This option reduces the number of
	advertised links while still providing shortest paths.		advertised links while still providing shortest paths.
	skipping to change at page 4, line 46 ¶		skipping to change at page 5, line 8 ¶
	(1) The MDR includes in its router-LSA a point-to-point (type 1) link		(1) The MDR includes in its router-LSA a point-to-point (type 1) link
	for each fully adjacent neighbor. (Note that the MDR becomes		for each fully adjacent neighbor. (Note that the MDR becomes
	adjacent with all of its neighbors.)		adjacent with all of its neighbors.)
	(2) Each non-MDR router includes in its router-LSA a point-to-point		(2) Each non-MDR router includes in its router-LSA a point-to-point
	link for each fully adjacent neighbor, and, if the router is		link for each fully adjacent neighbor, and, if the router is
	fully adjacent with the MDR, for each bidirectional neighbor j		fully adjacent with the MDR, for each bidirectional neighbor j
	such that the MDR's router-LSA includes a link to j.		such that the MDR's router-LSA includes a link to j.
	To provide rationale for the above procedure, let i and j be two		To provide rationale for the above procedure, let i and j be two non-
	non-MDR routers. Since the SPF calculation (Section 16.1 of		MDR routers. Since the SPF calculation (Section 16.1 of [RFC2328])
	[RFC2328]) allows router i to use router j as a next hop only if		allows router i to use router j as a next hop only if router j
	router j advertises a link back to router i, routers i and j must		advertises a link back to router i, routers i and j must both
	both advertise a link to each other in their router-LSAs before		advertise a link to each other in their router-LSAs before either can
	either can use the other as a next hop. Therefore, the above		use the other as a next hop. Therefore, the above procedure for non-
	procedure for non-MDR routers (Step 2) implies there must exist a		MDR routers (Step 2) implies there must exist a path of fully
	path of fully adjacent links between i and j (via the MDR) in		adjacent links between i and j (via the MDR) in both directions
	both directions before this can happen. The above procedure for		before this can happen. The above procedure for non-MDR routers is
	non-MDR routers is similar to one described in Section 4.6 of		similar to one described in Section 4.6 of [RFC6845] for non-DR
	[RFC6845] for non-DR routers.		routers.
	4. MDR Selection Algorithm		4. MDR Selection Algorithm
	The MDR selection algorithm of [RFC5614] simplifies as follows in		The MDR selection algorithm of [RFC5614] simplifies as follows in
	single-hop networks. The resulting algorithm is similar to the DR		single-hop networks. The resulting algorithm is similar to the DR
	election algorithm of OSPF, but is slightly different (e.g., two		election algorithm of OSPF, but is slightly different (e.g., two
	Backup MDRs are selected). The following simplified algorithm is		Backup MDRs are selected). The following simplified algorithm is
	interoperable with the full MDR selection algorithm.		interoperable with the full MDR selection algorithm.
	Note that lexicographic order is used when comparing tuples of the		Note that lexicographic order is used when comparing tuples of the
End of changes. 6 change blocks.
	21 lines changed or deleted		32 lines changed or added
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