On Wednesday 03 July 2002 13:02, Lee Fellows wrote: >On Wed, 2002-07-03 at 10:47, Scaglione Ermanno wrote: >> thanks but I found the real problem: there is a cisco router >> doing NAT between the amanda server and the two server. I found >> that it had a nat udp timeout of 6 minutes (CISCO default). What >> happens is that amanda gets the estimates from the first server >> that answers and starts the backup on that server, then the link >> becomes too busy, the UDP connection with the second server >> times out on the router and the second backup doesn't work >> ...... Well we could consider this an amanda bug maybe, the >> problem is that amanda doesn't do keepalive while sendsize runs, >> and sendsize itself doesn't do keepalive. I have been told that >> most CISCO routers doing NAT have this 6 minutes nat udp timeout >> thus if the estimate takes more than 6 minutes the backup will >> probably fails if there is such a router in between ..... >> >> ----- Original Message ----- >> From: "Chris Marble" <[EMAIL PROTECTED]> >> To: "Scaglione Ermanno" <[EMAIL PROTECTED]> >> Sent: Wednesday, July 03, 2002 4:39 AM >> Subject: Re: syncronize backups >> >> > Scaglione Ermanno wrote: >> > > I have a strange problem with amanda, I am backing up 6 >> > > servers with the same disklist and 2 of them alternatively >> > > fails with a timeout in >> >> sendsize. >> >> > > Server A works for a couple of days and server B doesn't in >> > > the same >> >> days, >> >> > > then server B works and server A doesn't. I suppose the >> > > reason is that >> >> both >> >> > > server are behind a slow link. How can I tell Amanda not to >> > > backup simultaneously the two servers using 1 disklist? >> > >> > Hmm, I was going to tell you to lie to Amanda and tell it that >> > all the >> >> disks >> >> > are on the same spindle. But then I realized that the spindle >> > parameter >> >> is >> >> > on a per-machine basis. You could set an earlier starttime >> > for those >> >> servers and >> >> > set inparallel to 1 just for a while. >> > -- >> > [EMAIL PROTECTED] - HMC UNIX Systems Manager > > Interesting. Do I understand your suggestion correctly to imply > that keepalive be done on udp sockets. If so, might I suggest > that this is not the solution. Its been several years since I > programmed tcp and udp clients and servers, but if memory serves > me correctly, keepalive is only available in the tcp-family of > protocols. Keepalive was intended to maintain an otherwise idle > connection for some period of time. Udp by definition is not a > connected protocol and such an option would be meaningless for > it.
On a FWIW note, the new iptstate-1.3.1 is showing that the cups daemons on my two machines are exchanging udp packets, effectively doing a keepalive on udp port 631. Its setting a TTL of 30 seconds, and renewing it at about 25 second intervals. So its not impossible to keep a udp connection alive full time. As to the RFC legality of such, I'll leave that to the experts. This connection isn't nat'd though as its between 192.168.x.x addresses. -- Cheers, Gene AMD K6-III@500mhz 320M Athlon1600XP@1400mhz 512M 99.04% setiathome rank, not too shabby for a WV hillbilly
