Illustrated TCP/IP by Matthew G. Naugle Wiley Computer Publishing, John Wiley & Sons, Inc. ISBN: 0471196568   Pub Date: 11/01/98

Chapter 158
Neighbor Discovery Types

This protocol solves a set of problems related to the interaction between nodes attached to the same link. It defines mechanisms for solving each of the following problems:

Router Discovery. This protocol allows hosts to locate and identify routers on their local link.

Prefix Discovery. How hosts discover the set of address prefixes that define which destinations are on-link for an attached link. (Nodes use prefixes to distinguish destinations that reside on-link from those only reachable through a router.)

Parameter Discovery. How a node learns such link parameters as the link MTU or such Internet parameters as the hop-limit value to place in outgoing packets.

Address Autoconfiguration. How nodes automatically configure an address for an interface.

Address Resolution. How nodes determine the link-layer address of an on-link destination (e.g., a neighbor) given only the destination’s IP address.

Next-Hop Determination. The algorithm for mapping an IP destination address into the IP address of the neighbor to which traffic for the destination should be sent. The next-hop can be a router or the destination itself.

Neighbor Unreachability Detection. How nodes determine that a neighbor is no longer reachable. For neighbors used as routers, alternate default routers can be tried. For both routers and hosts, address resolution can be performed again.

Duplicate Address Detection. How a node determines that an address it wishes to use is not already in use by another node.

Redirect. How a router informs a host of a better first-hop node to reach a particular destination.

Also contained in RFC 792 is the original ICMP redirect message in which a router sends to a host stating, “I will forward the packet that you sent to me to my next hop port. However, there is a better path to the destination that you indicated and it is through Router X.”