Version User Scope of changes
Jun 5 2008, 4:44 AM EDT (current) sbanerj1 4 words added, 1 word deleted
Jun 4 2008, 10:15 PM EDT sbanerj1 924 words added

Changes

Key:  Additions   Deletions
Taking off from where we last left off, the physical hosts Scofield and Montgomery were connected point-to-point and were communicating with the network settings that were auto-configured by the Avahi-daemon. Today we manually configured the network settings ourselves and were able to ssh

The IP addresses selected were 200.0.1.1 for Scofield and 200.0.1.2 for Montgomery. The addresses were selected such so as to not conflict with private addresses of the form 192.x.x.x. When we first tried the traceroute and tcptraceroute programs to see if we could talk from one machine to another, we received timed out messages, and other times the output was taking an abnormally large time. After restarting both machines we tried the same procedures, while simultaenously having tcpdump capture packets on from the eth0 interface as we tried the traceroute, tcptraceroute, and ssh programs from Scofield to Montgomery.

Everything worked as expected, however the programs took significant time to display information communicated across the p2p connection. However what was puzzling was that when check the transfer rate of copying a file from Montgomery to Scofield, a high transfer rate was achieved. The following is an excerpt of the tcpdump program running on Montgomery while Scofield was talking to it:it across the p2p connection from one physical host to the other.

16:13:55.496499 arp who-has 147.129.1.2 tell montgomery.local
16:13:56.496494 arp who-has 147.129.1.2 tell montgomery.local
16:13:57.496494 arp who-has 147.129.1.2 tell montgomery.local
16:14:00.496492 arp who-has 147.129.94.4 tell montgomery.local
16:14:01.496494 arp who-has 147.129.94.4 tell montgomery.local
16:14:02.496494 arp who-has 147.129.94.4 tell montgomery.local
16:14:03.496509 arp who-has 216.54.204.186 tell montgomery.local
16:14:04.496493 arp who-has 216.54.204.186 tell montgomery.local
16:14:05.496494 arp who-has 216.54.204.186 tell montgomery.local
16:14:09.496492 arp who-has 147.129.1.2 tell montgomery.local
16:14:10.496493 arp who-has 147.129.1.2 tell montgomery.local
16:14:11.496493 arp who-has 147.129.1.2 tell montgomery.local
16:14:14.496492 arp who-has 147.129.94.4 tell montgomery.local
16:14:15.496493 arp who-has 147.129.94.4 tell montgomery.local
16:14:16.496493 arp who-has 147.129.94.4 tell montgomery.local
16:14:17.496511 arp who-has 216.54.204.186 tell montgomery.local
16:14:18.496493 arp who-has 216.54.204.186 tell montgomery.local
16:14:19.496493 arp who-has 216.54.204.186 tell montgomery.local
16:14:22.159259 IP scofield.local.44524 > montgomery.local.ssh: S 864220585:864220585(0) win 5840
<mss 1460,sackOK,timestamp 41858 0,nop,wscale 6>
16:14:22.159290 IP montgomery.local.ssh > scofield.local.44524: S 731914807:731914807(0) ack 8642
20586 win 5792 <mss 1460,sackOK,timestamp 95086 41858,nop,wscale 6>
16:14:22.159447 IP scofield.local.44524 > montgomery.local.ssh: . ack 1 win 92 <nop,nop,timestamp
41858 95086>
16:14:22.165936 IP montgomery.local.ssh > scofield.local.44524: P 1:41(40) ack 1 win 91 <nop,nop,
timestamp 95088 41858>
16:14:22.166035 IP scofield.local.44524 > montgomery.local.ssh: . ack 41 win 92 <nop,nop,timestam
p 41859 95088>
16:14:22.166136 IP scofield.local.44524 > montgomery.local.ssh: P 1:41(40) ack 41 win 92 <nop,nop
,timestamp 41859 95088>
16:14:22.166149 IP montgomery.local.ssh > scofield.local.44524: . ack 41 win 91 <nop,nop,timestam
p 95088 41859>

Looking at the above excerpt of output, we realized that even though we had manually configured the p2p connection, the local ithaca DNS servers were being queried to verify the authenticity of the other connection. We checked the /etc/resolve.conf file and saw that 3 redundant DNS servers were listed there to be queried. Removing those entries did the trick. We were thereafter able to efficiently communicate across the p2p connection without any significant lags or problems.

The following output is from Montgomery which logs into Scofield via ssh and then executes traceroute and tcptraceroute programs:
reichsfuhrer@montgomery:~$ ssh 200.0.1.1
reichsfuhrer@200.0.1.1's password:
Linux scofield 2.6.24-17-generic #1 SMP Thu May 1 14:31:33 UTC 2008 i686

The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.

To access official Ubuntu documentation, please visit:
http://help.ubuntu.com/
Last login: Wed Jun 4 17:02:33 2008 from montgomery.local
reichsfuhrer@scofield:~$ echo Sco to Wes
Sco to Wes
reichsfuhrer@scofield:~$ traceroute 200.0.1.1
traceroute to 200.0.1.1 (200.0.1.1), 30 hops max, 40 byte packets
1 scofield.local (200.0.1.1) 0.054 ms 0.012 ms 0.012 ms
reichsfuhrer@scofield:~$ traceroute 200.0.1.2
traceroute to 200.0.1.2 (200.0.1.2), 30 hops max, 40 byte packets
1 montgomery.local (200.0.1.2) 0.240 ms 0.210 ms 0.198 ms
reichsfuhrer@scofield:~$ tcptraceroute 200.0.1.1
Selected device lo, address 200.0.1.1, port 53994 for outgoing packets
Tracing the path to 200.0.1.1 on TCP port 80 (www), 30 hops max
1 scofield.local (200.0.1.1) [closed] 0.048 ms 0.026 ms 0.018 ms
reichsfuhrer@scofield:~$ tcptraceroute 200.0.1.2
Selected device eth0, address 200.0.1.1, port 35946 for outgoing packets
Tracing the path to 200.0.1.2 on TCP port 80 (www), 30 hops max
1 montgomery.local (200.0.1.2) [closed] 0.151 ms 0.135 ms 0.117 ms
reichsfuhrer@scofield:~$ logout
Connection to 200.0.1.1 closed.
reichsfuhrer@montgomery:~$

and this is the respective tcpdump running on Scofield:

reichsfuhrer@scofield:~$ sudo tcpdump -i eth0
[sudo] password for reichsfuhrer:
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
17:02:23.878276 arp who-has scofield.local tell montgomery.local
17:02:24.125336 arp reply scofield.local is-at 00:13:72:77:d7:5f (oui Unknown)
17:02:23.878351 IP montgomery.local.34145 > scofield.local.ssh: S 2837644429:2837644429(0) win 58
40 <mss 1460,sackOK,timestamp 813328 0,nop,wscale 6>
17:02:23.878374 IP scofield.local.ssh > montgomery.local.34145: S 2975479000:2975479000(0) ack 28
37644430 win 5792 <mss 1460,sackOK,timestamp 760064 813328,nop,wscale 6>
17:02:23.878490 IP montgomery.local.34145 > scofield.local.ssh: . ack 1 win 92 <nop,nop,timestamp
813329 760064>
17:02:23.929136 IP scofield.local.ssh > montgomery.local.34145: P 1:41(40) ack 1 win 91 <nop,nop,
timestamp 760077 813329>
17:02:23.929280 IP montgomery.local.34145 > scofield.local.ssh: . ack 41 win 92 <nop,nop,timestam
p 813342 760077>
17:02:23.929385 IP montgomery.local.34145 > scofield.local.ssh: P 1:41(40) ack 41 win 92 <nop,nop
,timestamp 813342 760077>
17:02:23.929396 IP scofield.local.ssh > montgomery.local.34145: . ack 41 win 91 <nop,nop,timestam
p 760077 813342>
17:02:23.929608 IP montgomery.local.34145 > scofield.local.ssh: P 41:833(792) ack 41 win 92 <nop,
nop,timestamp 813342 760077>
17:02:23.929613 IP scofield.local.ssh > montgomery.local.34145: . ack 833 win 116 <nop,nop,timest
amp 760077 813342>

NOTE: Notice the difference at the beginning between this tcpdump and the previous one