Hello, I'm confused by your statement that BGP is limited to 4096. I have BGP peers up with 8192:
tcp4 0 0 10.10.80.50.179 10.10.80.52.63812 ESTABLISHED sndsbcc: 0 sndsbmbcnt: 0 sndsbmbmax: 131072 sndsblowat: 2048 sndsbhiwat: 16384 rcvsbcc: 0 rcvsbmbcnt: 0 rcvsbmbmax: 131072 rcvsblowat: 1 rcvsbhiwat: 16384 proc id: 0 proc name: iss: 2525048599 sndup: 2525116373 snduna: 2525116373 sndnxt: 2525116373 sndwnd: 16384 sndmax: 2525116373 sndcwnd: 16384 sndssthresh: 1073725440 irs: 1970444719 rcvup: 1970506707 rcvnxt: 1970506707 rcvadv: 1970523091 rcvwnd: 16384 rtt: 0 srtt: 3361 rttv: 126 rxtcur: 1200 rxtshift: 0 rtseq: 2525116354 rttmin: 1000 mss: 8192 flags: REQ_SCALE RCVD_SCALE REQ_TSTMP RCVD_TSTMP [0x30001e0] >From what I've been able to tell the peers negotiate the MSS as high as >possible as a multiple of a power of 2. Serge ----- Original Message ---- From: Richard A Steenbergen <r...@e-gerbil.net> To: Mark Tinka <mti...@globaltransit.net> Cc: juniper-nsp@puck.nether.net Sent: Wed, June 1, 2011 9:49:51 PM Subject: Re: [j-nsp] SSH/Telnet session hanging On Thu, Jun 02, 2011 at 02:16:32AM +0800, Mark Tinka wrote: > > We have two networks, they all run Jumbo frames across the > board. One does 9,192 bytes, the other does 9,000 bytes. > > In all cases, we decided to set the 'tcp-mss' in Junos > systems to 1,500 bytes, which is the lowest MTU we have in > our network - toward our upstreams and peers. Well first off I hope you actually meant "something LOWER than 1500 bytes", since tcp-mss doesn't include the headers that go into making up the 1500 byte IP packet. At a minimum you're looking at 20 bytes of IP + 20 bytes of TCP, so an mss of 1460, but don't forget to leave room for things like TCP MD5. But more importantly, the maximum packet size for BGP is limited to 4096 anyways, so the 9000 vs 9192 path mtu really doesn't make any difference at all. :) I suppose I could also take this opportunity to gripe about an ongoing bug where Juniper's TCP stack occasionally thinks that the mss is ~64k, resulting in blackholing of the tcp packets and endlessly flapping sessions, but if I get started bitching about new junos bugs that are making my life hell right now I might not be able to stop. :( -- Richard A Steenbergen <r...@e-gerbil.net> http://www.e-gerbil.net/ras GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC) _______________________________________________ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp _______________________________________________ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp