Subject: [manet] the definition of neighbor

From: www triste <[email-masked]>
Date: Wed, 3 May 2006 13:35:11 +0200 (CEST)

Hello everybody
  i want to know what is the real definition of neighbor?
  x is neighbor of y = distance between x and y < 250 (and why exactly 250)
   
  or
   
  x is neighbor of y=y can receive hello paquets
   
  (i discuss in general,with olsr,aodv,dsdv .... routing protocols)
   
  Thanks for help or indication, 

---------------------------------
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From: Fred Baker <[email-masked]>
Date: Wed, 3 May 2006 10:06:09 -0700

The real definition of a neighbor, in any routing protocol, is a  
routing process that this routing process may communicate with  
directly, as opposed to one that must be reached via an intermediary  
at the same layer. Note that there may be intermediaries at a lower  
layer, through, such as a layer 2 switch or (in the case of BGP) an  
IP route within this AS to a system in a neighboring AS.

RFC 1142 (IS-IS) defines "Neighbour" as "An adjacent system reachable  
by traversal of a single subnetwork by a PDU."

RFC 2328 (OSPF) states this in the words: "Two routers that have  
interfaces to a common network".

RFC 4271 (BGP4) uses it in two senses: a neighboring system is a BGP  
process (identified by an IP address) that a TCP connection will be  
made to or accepted from, and a neighboring AS is the AS that a given  
route was received from.

RFC 3561 (AODV) doesn't define the word in so many words, but it  
makes some interesting assumptions about neighbors that become a  
definition. In its protocol description, it says that "Whenever a  
node receives a Hello message from a neighbor" certain things happen,  
and it notes that 'each node keeps a "precursor list", containing the  
IP address for each its neighbors that are likely to use it as a next  
hop towards each destination.' A neieghbor in AODV, by inference, is  
any node that a given node might receive an AODV message (and  
especially a HELLO) directly from.

RFC 3684 (TBRPF) defines:
    neighbor node
       A node j is said to be a neighbor of node i if node i can hear
       node j on some interface.  Node j is said to be a 2-way neighbor
       if there is a bidirectional link between i and j.

RFC 3626 (OLSR) keeps track of neighbors, two hop neighbors  
(neighbors of neighbors), and nodes further away. It therefore spends  
quite a bit of effort on the definition of the concept. It defines:

       neighbor node

          A node X is a neighbor node of node Y if node Y can hear  
node X
          (i.e., a link exists between an OLSR interface on node X  
and an
          OLSR interface on Y).

       2-hop neighbor

          A node heard by a neighbor.

       strict 2-hop neighbor

          a 2-hop neighbor which is not the node itself or a neighbor of
          the node, and in addition is a neighbor of a neighbor, with
          willingness different from WILL_NEVER, of the node.

          A node which is selected by its 1-hop neighbor, node X, to
          "re-transmit" all the broadcast messages that it receives from
          X, provided that the message is not a duplicate, and that the
          time to live field of the message is greater than one.

          A node which has selected its 1-hop neighbor, node X, as its
          multipoint relay, will be called a multipoint relay  
selector of
          node X.

       symmetric 1-hop neighborhood

          The symmetric 1-hop neighborhood of any node X is the set of
          nodes which have at least one symmetric link to X.

       symmetric 2-hop neighborhood

          The symmetric 2-hop neighborhood of X is the set of nodes,
          excluding X itself, which have a symmetric link to the
          symmetric 1-hop neighborhood of X.

       symmetric strict 2-hop neighborhood

          The symmetric strict 2-hop neighborhood of X is the set of
          nodes, excluding X itself and its neighbors, which have a
          symmetric link to some symmetric 1-hop neighbor, with
          willingness different of WILL_NEVER, of X.

http://www.ietf.org/rfc/rfc1142.txt
1142 OSI IS-IS Intra-domain Routing Protocol. D. Oran, Ed.. February
      1990. (Format: TXT=425379, PS=1440951, PDF=490300 bytes) (Status:
      INFORMATIONAL)

http://www.ietf.org/rfc/rfc2328.txt
2328 OSPF Version 2. J. Moy. April 1998. (Format: TXT=447367 bytes)
      (Obsoletes RFC2178) (Also STD0054) (Status: STANDARD)

http://www.ietf.org/rfc/rfc4271.txt
4271 A Border Gateway Protocol 4 (BGP-4). Y. Rekhter, Ed., T. Li, Ed.,
      S. Hares, Ed.. January 2006. (Format: TXT=222702 bytes) (Obsoletes
      RFC1771) (Status: DRAFT STANDARD)

http://www.ietf.org/rfc/rfc3561.txt
3561 Ad hoc On-Demand Distance Vector (AODV) Routing. C. Perkins, E.
      Belding-Royer, S. Das. July 2003. (Format: TXT=90356 bytes)  
(Status:
      EXPERIMENTAL)

http://www.ietf.org/rfc/rfc3684.txt
3684 Topology Dissemination Based on Reverse-Path Forwarding (TBRPF).
      R. Ogier, F. Templin, M. Lewis. February 2004. (Format: TXT=107963
      bytes) (Status: EXPERIMENTAL)

http://www.ietf.org/rfc/rfc3626.txt
3626 Optimized Link State Routing Protocol (OLSR). T. Clausen, Ed., P.
      Jacquet, Ed.. October 2003. (Format: TXT=161265 bytes) (Status:
      EXPERIMENTAL)

On May 3, 2006, at 4:35 AM, www triste wrote:

> Faites de Yahoo! votre page d'accueil sur le web pour retrouver  
> directement vos services préférés : vérifiez vos nouveaux mails,  
> lancez vos recherches et suivez l'actualité en temps réel. Cliquez  
> ici.