RFC 2763 (rfc2763) - Page 2 of 5
Dynamic Hostname Exchange Mechanism for IS-IS
Alternative Format: Original Text Document
RFC 2763 Dynamic Hostname February 2000
There are several ways one could build such a table. One is via
static configurations. Another scheme that could be implemented is
via DNS lookups. In this document we propose a third solution. We
hope the proposed solution is easier and more manageable than static
mapping or DNS schemes.
2. Possible solutions
The obvious drawback of static configuration of mappings is the issue
of scalability and maintainability. The network operators have to
maintain the name tables. They have to maintain an entry in the table
for every router in the network. They have to maintain this table on
each router in the network. The effort to create and maintain these
static tables grows with the total number of routers on the network.
Changing the name or systemID of one router, or adding one new router
introduced will affect the configurations of all the other routers on
the network. This will make it very likely that those static tables
are outdated.
Having one table that can be updated in a centralized place would be
helpful. One could imagine using the DNS system for this. A drawback
is that during the time of network problems, the response time of DNS
services might not be satisfactory or the DNS services might not even
be available. Another possible drawback might be the added complexity
of DNS. Also, some DNS implementations might not support A and PTR
records for CLNS NSAPs.
A third way to build dynamic mappings would be to use the transport
mechanism of the routing protocol itself to advertise symbolic names
in IS-IS link-state PDU. This document defines a new TLV which allows
the IS-IS routers to include the name to systemID mapping information
in their LSPs. This will allow simple and reliable transport of name
mapping information across the IS-IS network.
3. The Dynamic Hostname TLV
The Dynamic hostname TLV is defined here as TLV type 137.
LENGTH - total length of the value field.
VALUE - a string of 1 to 255 bytes.
The Dynamic hostname TLV is optional. This TLV may be present in any
fragment of a non-pseudo node LSP. The value field identifies the
symbolic name of the router originating the LSP. This symbolic name
can be the FQDN for the router, it can be a subset of the FQDN or any
string operators want to use for the router. The use of FQDN or a
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