Path: utzoo!utgpu!water!watmath!clyde!bellcore!rutgers!mit-eddie!uw-beaver!teknowledge-vaxc!sri-unix!hplabs!hpda!hpcuhb!hpindda!daver From: daver@hpindda.HP.COM (Dave Richards) Newsgroups: comp.protocols.tcp-ip Subject: Re: a proposed modification to ARP Message-ID: <6200006@hpindda.HP.COM> Date: 11 Jul 88 17:20:18 GMT References: <8807092227.AA09479@hogg.cc.uoregon.edu> Organization: HP Technical Networks, Cupertino, Calif. Lines: 23 > Adding an additional HOST_DEAD state to the ARP tables could be used > to handle these cases; ARPs for dead hosts would be limited to no more > than one every minute or so. A sophisticated algorithm would arp very > frequently initially, but use a backoff to increase the delay between > successive ARPs as the number of consecutive non-responses increases. > This scheme also has the beneficial side effect of allowing IP to > return ICMP host unreachables for dead machines. I like this idea. LAN traces of our local network have illustrated that such a "state" is quite necessary. NFS and TCP traffic for down hosts generates sooo many ARPs, it's an nightmare. > 4.3 BSD ARP times out unaccessed cache entries every 20 minutes. Is > there any good reason not to increase the value to several hours or > longer? Broadcasts are expensive and memory is cheap. A number is just a number. But... 20 minutes isn't that short a time-period, with respect to most LANs. Also, directed ARP requests for cache entries being timeed-out, is one way of easing the burden on the network, ehile sllowing the cache entry to die in a moderate period of time. Dave Richards