RFC 1322 A Unified Approach to Inter-Domain Routing May 1992 5.2 Transition The proposed architecture is not intended for full deployment in the short term future. RFC 1322 A Unified Approach to Inter-Domain Routing May 1992 4.0 Source-demand routing (SDR) Inter-domain routers participating in the SDR component forward packets according to routing information computed and installed by the domain that originates the traffic (source routing domain). For example, even if a particular route from an intermediate transit domain X, to a destination domain Y is shared by 1,000 source-domains, IDPR requires that state for each of the 1,000 routes be setup and maintained in the transit border routers between X and Y. In contrast, an alternative approach to inter-domain routing, based on hop-by-hop routing and a distributed route-computation algorithm (described later), provides extensive support for aggregation and abstraction of reachability, topology, and forwarding information. In contrast, PV allows each domain to make its route selection autonomously, based only on local policies. In contrast, PV can accommodate heterogeneous route selection with little additional overhead. The latter always imposes less overhead than flooding. LISs, the source station must
forward data packets to a router that is a member of multiple LISs,
even though the source and destination stations may be on the same
logical NBMA network. Post has been c reated by GSA Content Generator D emoversion.
At the same time, since preserving each domain’s independence and autonomy is one of the crucial requirements of inter-domain routing, the architecture must strive for the maximum flexibility of its aggregation scheme, i.e., impose as few preconditions, and as little global coordination, as possible on the participating domains. Another reason for relaxed complexity requirements for SDR is that SDR is expected to compute routes to a smaller number of destinations than is NR (although SDR route computation may be invoked more frequently). With PV, topology changes only result in the recomputation of routes affected by these changes, which is more efficient than complete recomputation. Aggregating transit constraints with LS may result in either reduced connectivity or less information reduction, as compared with PV. As a result of having inter-LIS address resolution capability, NHRP
allows the communicating parties to exchange packets by fully
utilizing the particular features of the NBMA network. As such,
NHRP will be used in resolving the ATM addresses of MPOA packets
destined outside the originating subnet. NHRP is specified for resolving the destination NBMA addresses of IP
datagrams over IP subnets within a large NBMA cloud.
If NHRP uses the services of a dynamic routing
algorithm in fulfilling its function, which is necessary for robust
and scalable operation, then the exit router identified by NHRP
reflects the selection made by the network layer dynamic routing
protocol. If it is believed that the
adjacency of the destination station to the egress router is a stable
topological configuration, then NHRP can safely be used in this
router-router communication scenario. NHRP can be used in host-host, host-router and router-host
communications. 2)), we can selectively choose those that will be useful to compute routes. However, time dependency must be predictable (e.g., advertising a certain route only after business hours) and routes should be used widely enough to warrant inclusion in NR. 4.2.1 Configured Information Information about the existence of inter-domain links, and policies maintained by domains, changes slowly over time. We are proposing this architecture as a goal towards which we can begin guiding our operational and research investment over the next 5 years.
While routing number in USA are used for domestic wire transfers, swift codes are used for incoming international fund transfers. Who needs the GTE Financial Routing number? In general, the selection made by the routing protocol
would often reflect a desirable attribute, such as identifying the
exit router that induces the least number of hops in the original
routed path. In general, there may be multiple exit routers that have connectivity
to the destination. SDR requires that this graph be augmented by links with non-generic policies that have been discovered and maintained for computing special routes; in addition, special policy flags may be added to links already maintained by the NR component. We address two issues in turn: distribution of configured topology and policy information, and distribution of dynamic status information. An NHRP Server is the
one who issues a reply to an NHRP request, or the one who forwards a
received NHRP request to another Server.