Benefits and costs of multi-protocol routing
Scott M. Ballew
The common wisdom these days is that the networking world is inevitably converging on Internet Protocol (IP). And that may well be true, but there are still circumstances when other protocols can get jobs done more easily or more efficiently. How can you, as a network administrator, know when to deploy which network protocols? This tip, excerpted from Managing IP Networks with Cisco Routers, published by O'Reilly Associates, gives details.
The benefits of routing non-IP protocols are non trivial:
- Most network protocols are more similar than different. A router that can route one efficiently can generally route another efficiently.
- Routing non-IP protocols in a network's IP routers means that the protocols are administered by the same staff that administers the IP protocol family, reducing duplication of effort and equipment.
- Many non-IP protocols are the most efficient way for a LAN to operate. For example, Novell Netware (IPX) and Banyan Vines provide more efficient file and print services for a PC than IP's Network File System.
- Routing non-IP protocols increases the flexibility of your network to meet the needs of your users.
These considerations indicate that multi-protocol routing is a good thing, at least in the abstract. But there are equally good reasons to consider which, if any, non-IP protocols to route. These are some of the best reasons not to route non-IP protocols:
- Additional knowledge requirements. No one can be expert at everything, but you need an expert in each protocol that you route to understand its needs and diagnose its failures.
- Additional load on router equipment. Each routed protocol requires its own routing table, and possibly also its own dynamic routing protocol, which take memory and processing power.
- Increased complexity. A multi-protocol router is a far more complex piece of software and hardware than a single-protocol router, so weaknesses in the implementation of one protocol may affect the stability of the other protocols.
- More difficult design. Since each protocol family has its own rules for routing, address assignment and so on, and these rules often conflict with each other, you must put more care and thought into creating a design that handles all the protocols you need properly.
- Decreased scalability. Some protocols families do not scale as well as others, or may not work well in a WAN environment, thereby decreasing the size to which you can scale your network.
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