As per Relevance of the word information, we have this rfc below:
Network Working Group G.
Request for Comments: 2081
Category: Informational January 1997
RIPng Protocol Applicability
Status of this
This memo provides information for the Internet community. This
does not specify an Internet standard of any kind. Distribution
this memo is unlimited
As required by Routing Protocol Criteria (RFC 1264), this
defines the applicability of the RIPng protocol within the Internet
This report is a prerequisite to advancing RIPng on the
track
1. Protocol
The RIPng protocol description is defined in RFC 2080.
2.
This report describes how RIPng may be useful within the new IPv
Internet. In essence, the environments in which RIPng is the IGP
choice is comparable to the environments in which RIP-2 (RFC 1723)
used in the IPv4 Internet. It is important to remember that RIPng
a simple extrapolation of RIP-2; RIPng has nothing conceptually new
Thus, the operational aspects of distance-vector routing protocols
and RIP-2 in particular, within an autonomous system are
understood
It should be noted that RIPng is not intended to be a substitute
OSPFng in large autonomous systems; the restrictions on AS
and complexity which applied to RIP-2 also apply to RIPng. Rather
RIPng allows the smaller, simpler, distance-vector protocol to
used in environments which require authentication or the use
variable length subnet masks, but are not of a size or
which require the use of the larger, more complex, link-
protocol
The remainder of this report describes how each of the features
RIPng is useful within IPv6.
Malkin Informational [Page 1]
RFC 2081 RIP-2 Applicability January 1997
3.
A goal in developing RIPng was to make the minimum necessary
to RIP-2 to produce RIPng. In essence, the IPv4 address was
into an IPv6 address, the IPv4 subnet mask was replaced with an IPv
prefix length, the next-hop field was eliminated but
functionality has been preserved, and authentication was removed
The route tag field has been preserved. The maximum diameter of
network (the maximum metric value) is 15; 16 still means
(unreachable).
The basic RIP header is unchanged. However, the size of a
packet is no longer arbitrarily limited. Because routing updates
never forwarded, the routing packet size is now determined by
physical media and the sizes of the headers which precede the
data (i.e., media MTU minus the combined header lengths). The
routes which may be included in a routing update is the routing
length divided by the size of a routing entry
3.1
The address field of a routing entry is 128 bits in length,
from the 32 bits available in RIP-2. This allows the RIP entry
carry an IPv6 prefix
3.2 Prefix
The 32-bit RIP-2 subnet mask field is replaced by an 8-bit
length field. It allows the specification of the number of bits
the prefix which form the actual prefix
3.3 Next
The ability to specify the next hop, rather than simply allowing
recipient of the update to set the next hop to the sender of
update, allows for the elimination of unnecessary hops
routers which are running multiple routing protocols.
following example topology
----- ----- ----- -----
|IR1| |IR2| |XR1| |XR2|
--+-- --+-- --+-- --+--
| | | |
--+-------+-------------+-------+--
|--------RIPng--------|
Malkin Informational [Page 2]
RFC 2081 RIP-2 Applicability January 1997
The Internal Routers (IR1 and IR2) are only running RIPng.
External Routers (XR1 and XR2) are both running BGP, for example
however, only XR1 is running BGP and RIPng. Since XR2 is not
RIPng, the IRs will not know of its existance and will never use
as a next hop, even if it is a better next hop than XR1. Of course
XR1 knows this and can indicate, via the Next Hop mechanism, that XR
is the better next hop for some routes
3.4
Authentication, which was added to RIP-2 because RIP-1 did not
it, has been dropped from RIPng. This is safe to do because IPv6,
which carries the RIPng packets, has build in security which IPv4
not have
3.5 Packet
By allowing RIPng routing update packets to be as big as possible
the number of packets which must be sent for a complete update
greatly reduced. This in no way affects the operation of
distance-vector protocol; it is merely a performance enhancement
3.6 Diameter and
The limit of 15 cost-1 hops is a function of the distance-
protocol, which depends on counting to infinity to resolve
routing loops. If infinity is too high, the time it would take
resolve, not to mention the number of routing updates which would
sent, would be prohibitive. If the infinity is too small,
protocol becomes useless in a reasonably sized network. The
of 16 for infinity was made in the earliest of RIP
and experience has shown it to be a good compromise value
RIPng will efficiently support networks of moderate complexity.
is, topologies without too many multi-hop loops. RIPng
effeciently supports topologies which change frequently
routing table changes are made incrementally and do not require
computation which link-state protocols require to rebuild their maps
4.
Because the basic protocol is unchanged, RIPng is as correct
routing protocol as RIP-2. RIPng serves the same niche for IPv6
RIP-2 does for IPv4.
5. Security
RIPng security is discussed in section 3.4.
Malkin Informational [Page 3]
RFC 2081 RIP-2 Applicability January 1997
Author's
Gary Scott
Xylogics/Bay
53 Third
Burlington, MA 01803
Phone: (617) 238-6237
EMail: gmalkin@xylogics.
Malkin Informational [Page 4]
if you see any problems within the linking, don't worry be happy,
this is version 0.1 of the Relevance System and you gotta expect some crappy subroutines sometimes,
just be content we did not write this in Java, which would have made this "bigger and better" HAHAHHA.
RFC documents can be found at I.E.T.F.
Relevance System Copyright © 2002 Spectrum WorldResearch
other technical nosh by ServerMasters Corporation
collaboration of BobX
