Path: utzoo!utgpu!watserv1!watmath!att!linac!uwm.edu!lll-winken!sol.ctr.columbia.edu!ira.uka.de!smurf!urlichs From: urlichs@smurf.sub.org (Matthias Urlichs) Newsgroups: comp.protocols.tcp-ip Subject: Re: Internet Access Costs Message-ID: Date: 30 Nov 90 23:43:08 GMT References: <315@srchtec.UUCP> <1990Nov26.233848.20828@nmt.edu> <1990Nov29.212559.7284@spectrum.CMC.COM> Organization: University of Karlsruhe, FRG Lines: 33 In comp.protocols.tcp-ip, article <1990Nov29.212559.7284@spectrum.CMC.COM>, < < Crazy as it seems at first glance, dynamic IP addresses are < not actually all that unusual. Client-only PC's often do this. And with < domain name service, it is doable even to handle incoming connections. < < Yes, it does create a few management hassles. You need to have a < name server with a transaction interface to change the name/address < mappings on the fly (where the run-of-the-mill BIND just reads a table < when it is reloaded) and you cannot have management utilities that < assume that name/address mappings are constant. < Problem 1: Name server records get cached. A TTL of five minutes is probably not a good idea. Problem 2: What if my connection breaks (noisy phone line, idle connection timeout) and I have to reconnect? Suddenly my IP number is different: and the existing connection is broken for good. Not good either. < As to WHY one wants to do this ? When you have a couple hundred < PC's around, it is easier to just declare them to be generic than to try < to keep track of locations and owners for all of them. Likewise, network < providers may have only allocated class C network numbers for a routing < cluster, and may prefer the dynamic addresses over changing backbone < routing implementations with hardcoded netmasks. < That might work for PCs or similar clients, but for external SLIP/PPP connections (which might even have their own Class C network hanging off the remote end) it seems to be preferable to give each client its own IP address. -- Matthias Urlichs -- urlichs@smurf.sub.org -- urlichs@smurf.ira.uka.de /(o\ Humboldtstrasse 7 - 7500 Karlsruhe 1 - FRG -- +49+721+621127(0700-2330) \o)/ Brought to you by Super Global Mega Corp .com