October 2002
Intermediate to advanced
206 pages
8h 30m
English
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Using UDP versus TCP
A question frequently asked of the RADIUS development team is why the protocol uses the UDP protocol instead of TCP. For purely operational requirements, UDP was selected largely because RADIUS has a few inherent properties that are characteristic of UDP: RADIUS requires that failed queries to a primary authentication server be redirected to a secondary server, and to do this, a copy of the original request must exist above the transport layer of the OSI model. This, in effect, mandates the use of retransmission timers.
The protocol bets on the patience of users to wait for a response. It assumes some middle ground between lightning fast and slow as molasses. The RADIUS RFC describes it best: “At one extreme, RADIUS does not require a “responsive” detection of lost data. The user is willing to wait several seconds for the authentication to complete. The generally aggressive TCP retransmission (based on average round trip time) is not required, nor is the acknowledgment overhead of TCP. At the other extreme, the user is not willing to wait several minutes for authentication. Therefore the reliable delivery of TCP data two minutes later is not useful. The faster use of an alternate server allows the user to gain access before giving up.”
Since RADIUS is stateless (as I mentioned in Chapter 1), UDP seems natural, as UDP is stateless, too. With TCP, clients and servers must have special code or administrative workarounds to mitigate the effects of power losses, ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.