nanog mailing list archives
RE: barak-online.net icmp performance vs. traceroute/tcptraceroute, ssh, ipsec
From: "Lincoln Dale" <ltd () interlink com au>
Date: Mon, 7 May 2007 10:13:31 +1000
traceroute/tcptraceroute show packet loss and MUCH higher rtt than the corresponding direct pings on the reported hop entries. Is this some sort of massaging or plain just "faking it"? Or is such things merely net-urban myth?
the vast majority of routers on the internet respond very differently to traffic 'directed at them' as opposed to traffic 'routed through them'. many routers will punt traffic "at them" (such as icmp echo) to a low-priority control-plane (software) stack to respond to. this is vastly different to what may well be a hardware (ASIC) based forwarding path. many routers will also typically rate-limit the number of such queries they respond to per second. this may even be a tunable setting (e.g. CoPP on some Cisco products). i'd suggest that you don't try to read ANYTHING into comparing 'traceroute' with end-to-end icmp echo. nor that traceroute only shows one direction of traffic. if you have IPSec/SSH and/or TCP in general which simply "doesn't work right", i suggest you first verify that the end-to-end MTU is appropriate. my bet is that it isn't, and that PMTUD isn't working as expected because of some filtering and/or broken devices/configuration in the path. try sending pings at 1500 byte packets with DF set & see if they get through. my money is on they don't. cheers, lincoln.
Current thread:
- barak-online.net icmp performance vs. traceroute/tcptraceroute, ssh, ipsec Joe Maimon (May 06)
- RE: barak-online.net icmp performance vs. traceroute/tcptraceroute, ssh, ipsec Lincoln Dale (May 06)
- Re: barak-online.net icmp performance vs. traceroute/tcptraceroute, ssh, ipsec Joe Maimon (May 06)
- RE: barak-online.net icmp performance vs. traceroute/tcptraceroute, ssh, ipsec Lincoln Dale (May 06)
- Re: barak-online.net icmp performance vs. traceroute/tcptraceroute, ssh, ipsec Joe Maimon (May 06)
- Re: barak-online.net icmp performance vs. traceroute/tcptraceroute, ssh, ipsec Adrian Chadd (May 06)
- RE: barak-online.net icmp performance vs. traceroute/tcptraceroute, ssh, ipsec Lincoln Dale (May 06)
- Re: barak-online.net icmp performance vs. traceroute/tcptraceroute, ssh, ipsec Joe Maimon (May 06)
- Re: barak-online.net icmp performance vs. traceroute/tcptraceroute, ssh, ipsec Steven M. Bellovin (May 06)
- Re: barak-online.net icmp performance vs. traceroute/tcptraceroute, ssh, ipsec Joe Maimon (May 06)
- Re: barak-online.net icmp performance vs. traceroute/tcptraceroute, ssh, ipsec Jo Rhett (May 07)
- Re: barak-online.net icmp performance vs. traceroute/tcptraceroute, ssh, ipsec Joe Maimon (May 07)
- Re: barak-online.net icmp performance vs. traceroute/tcptraceroute, ssh, ipsec Peter Dambier (May 07)
- RE: barak-online.net icmp performance vs. traceroute/tcptraceroute, ssh, ipsec Lincoln Dale (May 06)