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Distance vector routing algorithm RIP uses hop count as a routing metric. Why it is not using delay as a metric ?

joeqwerty
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Parth Umeshbhai Patel
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    Because that's the way it was designed? – joeqwerty Oct 13 '13 at 22:32
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    I answered this one because it was easy; however, it will be a good idea for you to read the "help" link at the top. If you're asking a question about a real problem (either in reality or design), then give some more details about the actual problem. If you're asking a pure "why is X done with Y", that's not a great question per the intent of this site. – mfinni Oct 13 '13 at 22:37
  • Adding some context to your question can be very helpful. What are you trying to achieve? What problem are you facing? – Drew Khoury Oct 14 '13 at 01:29

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Because it was not designed for it.

https://www.rfc-editor.org/rfc/rfc2453

This protocol uses fixed "metrics" to compare alternative routes. It is not appropriate for situations where routes need to be chosen based on real-time parameters such a measured delay, reliability, or load. The obvious extensions to allow metrics of this type are likely to introduce instabilities of a sort that the protocol is not designed to handle.

Community
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mfinni
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Most routing protocols use statically assigned metrics — RIP, OSPF, EIGRP, BGP. In RIP, the default metric is 1, which is called the "hop count" metric. While it is possible to assign larger metrics to links in RIP, this is not recommended, since it reduces the maximum diameter of the network (RIP metrics are limited to 15).

Using dynamically computed metrics in your routing protocol is a difficult problem. Done naively, it will create a negative feedback loop, which will cause persistent routing oscillations.

We have done some experiments with dynamically computed delay-based metrics. In short, it can be made to work, but it's tricky.

jch
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