NHRP is particularly applicable for environments where the
decision on local vs. RFC 1322 A Unified Approach to Inter-Domain Routing May 1992 In summary, when a route is first installed, the source has several options (which are represented by flags in the route setup packet): 1. If an NR route is available that satisfies all local policy and TOS, then use it. RFC 1322 A Unified Approach to Inter-Domain Routing May 1992 During route installation, if a BR on the path finds that the remainder of the indicated route from the BR to the destination is identical to the NR route from the BR to the destination, then the BR can turn off the SDR route at that point and map it onto the NR route. RFC 1322 A Unified Approach to Inter-Domain Routing May 1992 computation. In order to avoid such an undesirable situation, a
useful operation rule is to authorize only the following entities to
issue an NHRP request and to perform short-cut routing. The entities responsible for exchanging inter-domain routing information are called route servers (RSs). Thus, when used in conjunction
with dynamic routing algorithms, at the NHRP domain level, NHRP
should scale in the same order as the routing algorithm, subject to
the assumption that all the routers along the path are NHRP aware. Art icle has be en generated by GSA C ontent Gen erator DEMO!
Thus, when NHRP is implemented in conjunction with dynamic network
layer routing, a scaling requirement for NHRP is that virtually all
the routers within a logical NBMA network should be NHRP aware. Dynamic network layer routing
protocols are proven to scale well. In this context, it is the job of routing protocols to locate routes that can potentially support the particular TOS requested. In general, routing
protocols are used to determine the proper path from a source host or
router, or intermediate router, to a particular destination. Given the difficulties of supporting LS hop-by-hop routing in the presence of (a) flexible aggregation, (b) heterogeneous route selection policies, and (c) incomplete or inconsistent routing information, we see no alternative but to employ PV for the NR component of our architecture. While the number and variety of routes provided by hop-by-hop routing architectures with type of service (TOS) support (i.e., multiple, tagged routes) may be sufficient for a large percentage of traffic, it is important that mechanisms be in place to support efficient routing of specialized traffic types via special routes. While storage and bandwidth overhead may be interrelated, if incremental updates are used then bandwidth overhead is negligible in the steady state (no changes in topology), and is independent of the storage overhead.
How the RSs should define filters that will get enough information to find special routes, while also effectively limiting the information, is an open question. This is really just a corollary to the above; i.e., if we allow route selection policy to be expressed for NR routes, we can not assume all domains will apply the same policy. 3.4 Aggregation Forming confederations of domains, for the purpose of consistent, hop-by-hop, LS route computation, requires that domains within a confederation have consistent policies. In addition, aggregation should not require explicit designation of the relative placement of each domain relative to another; i.e., domains or confederations of domains should not be required to agree on a partial ordering (i.e., who is above whom, etc.). Support for confederations should be flexible. The focus is on scalability to very large networks and functionality, as well as scalability, to support routing in an environment of heterogeneous services, requirements, and route selection criteria. Furthermore, what is the routing number for GTE Federal Credit Union? This is because routers generally deal with an aggregation
of traffic from multiple sources, which in turn creates a potentially
large number of SVCCs out of the router’s NBMA interface. At the LIS level, the main issue is to maintain and deliver a sizable
number of NBMA to Network layer address mappings within large LISs.
Note: The work of D. Estrin and S. Hotz was supported by the National Science Foundation under contract number NCR-9011279, with matching funds from GTE Laboratories. Further work is needed to specify protocol in support for the NR component for ST-II. Section 5 describes protocol support for the unified architecture. Rekhter, Y., and D. Farinacci, “Support for Sparse Mode PIM over
ATM”, Work in Progress. Greene, M., and J. Luciani, “NHRP Management Information Base”,
Work in Progress. Generally, an NHRP request can be issued by a variety of NHRP
aware entities, including hosts and routers with NBMA interfaces. Then, not
all the routers in the NBMA network need to be NHRP aware. That is,
since the routers that need to process NHRP control messages are
specified by static routing, routers that are not included in the
manually defined static paths do not have to be NHRP aware. If
an IP packet traverses multiple hops before a short-cut path has been
established, then there is a chance that multiple short-cut paths
could be formed. In host-
router, or router-host communications, frequent changes in routed
paths could result in inefficiencies such as frequent creation of
short-cut paths which are short lived. This post was written by GSA Content Gener ator DEMO.