On 17 Mar, 2011, at 12:48 am, Fred Baker wrote: >> This reminds me of a related concept, using the TTL really as 'Time To Live' >> (in today's IP, it's more of a 'Remaining Hop Count). According to RfC 791, >> a router that buffers a packet by n seconds must decrease its TTL by n. I >> doubt that many routers implement this properly. > > There is, of course, a fundamental bug in that, noted in RFC 970. > > RFC 1812, which I edited, contains this text (that I didn't write): > > In this specification, we have reluctantly decided to follow the > strong belief among the router vendors that the time limit > function should be optional.
The major problem with the original TTL spec was that a router generally doesn't keep a packet for an integer number of seconds (at least, not in anything but the most ancient of hardware). If three separate routers each buffer for 350ms, that's about 1 second elapsed, but there is no way for the routers to indicate this to each other. Yet the TTL field was an integer number of seconds. The later hop-count spec is much saner. - Jonathan _______________________________________________ Bloat mailing list [email protected] https://lists.bufferbloat.net/listinfo/bloat
