From 4bfd864f10b68b71482b35c818559068ef8d5797 Mon Sep 17 00:00:00 2001 From: Thomas Voss Date: Wed, 27 Nov 2024 20:54:24 +0100 Subject: doc: Add RFC documents --- doc/rfc/rfc2081.txt | 227 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 227 insertions(+) create mode 100644 doc/rfc/rfc2081.txt (limited to 'doc/rfc/rfc2081.txt') diff --git a/doc/rfc/rfc2081.txt b/doc/rfc/rfc2081.txt new file mode 100644 index 0000000..910caa1 --- /dev/null +++ b/doc/rfc/rfc2081.txt @@ -0,0 +1,227 @@ + + + + + + +Network Working Group G. Malkin +Request for Comments: 2081 Xylogics +Category: Informational January 1997 + + + RIPng Protocol Applicability Statement + +Status of this Memo + + This memo provides information for the Internet community. This memo + does not specify an Internet standard of any kind. Distribution of + this memo is unlimited. + +Abstract + + As required by Routing Protocol Criteria (RFC 1264), this report + defines the applicability of the RIPng protocol within the Internet. + This report is a prerequisite to advancing RIPng on the standards + track. + +1. Protocol Documents + + The RIPng protocol description is defined in RFC 2080. + +2. Introduction + + This report describes how RIPng may be useful within the new IPv6 + Internet. In essence, the environments in which RIPng is the IGP of + choice is comparable to the environments in which RIP-2 (RFC 1723) is + used in the IPv4 Internet. It is important to remember that RIPng is + 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 well + understood. + + It should be noted that RIPng is not intended to be a substitute for + OSPFng in large autonomous systems; the restrictions on AS diameter + and complexity which applied to RIP-2 also apply to RIPng. Rather, + RIPng allows the smaller, simpler, distance-vector protocol to be + used in environments which require authentication or the use of + variable length subnet masks, but are not of a size or complexity + which require the use of the larger, more complex, link-state + protocol. + + The remainder of this report describes how each of the features of + RIPng is useful within IPv6. + + + + + +Malkin Informational [Page 1] + +RFC 2081 RIP-2 Applicability January 1997 + + +3. Applicability + + A goal in developing RIPng was to make the minimum necessary change + to RIP-2 to produce RIPng. In essence, the IPv4 address was expanded + into an IPv6 address, the IPv4 subnet mask was replaced with an IPv6 + prefix length, the next-hop field was eliminated but the + functionality has been preserved, and authentication was removed. + The route tag field has been preserved. The maximum diameter of the + network (the maximum metric value) is 15; 16 still means infinity + (unreachable). + + The basic RIP header is unchanged. However, the size of a routing + packet is no longer arbitrarily limited. Because routing updates are + never forwarded, the routing packet size is now determined by the + physical media and the sizes of the headers which precede the routing + data (i.e., media MTU minus the combined header lengths). The number + routes which may be included in a routing update is the routing data + length divided by the size of a routing entry. + +3.1 Prefix + + The address field of a routing entry is 128 bits in length, expanded + from the 32 bits available in RIP-2. This allows the RIP entry to + carry an IPv6 prefix. + +3.2 Prefix Length + + The 32-bit RIP-2 subnet mask field is replaced by an 8-bit prefix + length field. It allows the specification of the number of bits in + the prefix which form the actual prefix. + +3.3 Next Hop + + The ability to specify the next hop, rather than simply allowing the + recipient of the update to set the next hop to the sender of the + update, allows for the elimination of unnecessary hops through + routers which are running multiple routing protocols. Consider + 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. The + External Routers (XR1 and XR2) are both running BGP, for example; + however, only XR1 is running BGP and RIPng. Since XR2 is not running + RIPng, the IRs will not know of its existance and will never use it + 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 XR2 + is the better next hop for some routes. + +3.4 Authentication + + Authentication, which was added to RIP-2 because RIP-1 did not have + it, has been dropped from RIPng. This is safe to do because IPv6, + which carries the RIPng packets, has build in security which IPv4 did + not have. + +3.5 Packet Length + + By allowing RIPng routing update packets to be as big as possible, + the number of packets which must be sent for a complete update is + greatly reduced. This in no way affects the operation of the + distance-vector protocol; it is merely a performance enhancement. + +3.6 Diameter and Complexity + + The limit of 15 cost-1 hops is a function of the distance-vector + protocol, which depends on counting to infinity to resolve some + routing loops. If infinity is too high, the time it would take to + resolve, not to mention the number of routing updates which would be + sent, would be prohibitive. If the infinity is too small, the + protocol becomes useless in a reasonably sized network. The choice + of 16 for infinity was made in the earliest of RIP implementations + and experience has shown it to be a good compromise value. + + RIPng will efficiently support networks of moderate complexity. That + is, topologies without too many multi-hop loops. RIPng also + effeciently supports topologies which change frequently because + routing table changes are made incrementally and do not require the + computation which link-state protocols require to rebuild their maps. + +4. Conclusion + + Because the basic protocol is unchanged, RIPng is as correct a + routing protocol as RIP-2. RIPng serves the same niche for IPv6 as + RIP-2 does for IPv4. + +5. Security Considerations + + RIPng security is discussed in section 3.4. + + + +Malkin Informational [Page 3] + +RFC 2081 RIP-2 Applicability January 1997 + + +Author's Address + + Gary Scott Malkin + Xylogics/Bay Networks + 53 Third Avenue + Burlington, MA 01803 + + Phone: (617) 238-6237 + EMail: gmalkin@xylogics.com + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Malkin Informational [Page 4] + -- cgit v1.2.3