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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical UDP lossage (was: Types of packet modifications allowed for networks)
I was reminded by the "packet modifications" thread that it seems that dropping (rather than fragmenting) large UDP packets has become quite the norm, which is unfortunate. We're working on a (popular software) product that sends UDP datagrams (with DF cleared), and it is amazing how small they have to be to get through. Between the Cisco VPN software and the high-end NAT boxes that have broken hairpin behavior and broken consumer "routers", we're finding that whereas sizes in the mid 1400-byte range used to be safe, going much over 1200 bytes is now routinely a problem. Path MTU discovery (PLPMTUD) shouldn't need to be looking for and finding black holes when the DF flag is cleared, but that's what we're having to implement to work on today's Internet. Operational relevance: 1) This software will be running on your networks, and your customers will be happier if you don't drop UDP datagrams that are of reasonable size, 2) Knowing that this is going on might help you debug problems customers are having with other applications if you didn't know already how bad it has gotten. Matthew Kaufman [email protected] http://www.matthew.at
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