[173916] in North American Network Operators' Group
RTT of ICMP "TTL exceeded" messages in Level3 network remains the
daemon@ATHENA.MIT.EDU (Martin T)
Wed Aug 13 11:28:41 2014
X-Original-To: nanog@nanog.org
Date: Wed, 13 Aug 2014 18:25:11 +0300
From: Martin T <m4rtntns@gmail.com>
To: nanog@nanog.org
Errors-To: nanog-bounces@nanog.org
Hi,
if I make a traceroute to a host in San Jose in Level3 network from
DigitalOcean server in Amsterdam, then in Level3 network(hop 6 in
example below) the RTT remains the same:
# traceroute -q 1 -I ZYNGA-INC.edge1.SanJose3.Level3.net
traceroute to ZYNGA-INC.edge1.SanJose3.Level3.net (4.53.208.114), 30
hops max, 60 byte packets
1 5.101.103.253 (5.101.103.253) 0.265 ms
2 95.85.0.229 (95.85.0.229) 0.236 ms
3 ix-4-2-0-0.tcore1.AV2-Amsterdam.as6453.net (195.219.194.25) 0.275 ms
4 if-7-2.tcore1.AD1-Amsterdam.as6453.net (195.219.194.46) 0.630 ms
5 4.68.63.41 (4.68.63.41) 0.635 ms
6 vl-3603-ve-227.csw2.Amsterdam1.Level3.net (4.69.162.153) 155.309 ms
7 ae-56-221.ebr2.Amsterdam1.Level3.net (4.69.153.201) 155.627 ms
8 ae-46-46.ebr2.London1.Level3.net (4.69.143.74) 153.470 ms
9 *
10 ae-61-61.csw1.NewYork1.Level3.net (4.69.134.66) 148.972 ms
11 *
12 ae-2-2.ebr1.SanJose1.Level3.net (4.69.135.185) 147.881 ms
13 ae-91-91.csw4.SanJose1.Level3.net (4.69.153.14) 149.632 ms
14 ae-4-90.edge1.SanJose3.Level3.net (4.69.152.208) 151.107 ms
15 ZYNGA-INC.edge1.SanJose3.Level3.net (4.53.208.114) 154.431 ms
#
In other words, one sees the RTT of the end-host as a RTT for all the
hops in Level3 netwotk. If I make the traceroute to penultimate hop
ae-4-90.edge1.SanJose3.Level3.net, then RTT is as expected:
root@vserver:~# traceroute -q 1 -I ae-4-90.edge1.SanJose3.Level3.net
traceroute to ae-4-90.edge1.SanJose3.Level3.net (4.69.152.208), 30
hops max, 60 byte packets
1 5.101.103.254 (5.101.103.254) 0.228 ms
2 95.85.0.237 (95.85.0.237) 0.217 ms
3 ix-4-2-0-0.tcore1.AV2-Amsterdam.as6453.net (195.219.194.25) 0.276 ms
4 if-7-2.tcore1.AD1-Amsterdam.as6453.net (195.219.194.46) 0.656 ms
5 4.68.63.41 (4.68.63.41) 0.607 ms
6 vl-3604-ve-228.csw2.Amsterdam1.Level3.net (4.69.162.157) 0.696 ms
7 ae-56-221.ebr2.Amsterdam1.Level3.net (4.69.153.201) 0.677 ms
8 ae-45-45.ebr2.London1.Level3.net (4.69.143.70) 7.059 ms
9 ae-44-44.ebr1.NewYork1.Level3.net (4.69.137.78) 76.311 ms
10 ae-81-81.csw3.NewYork1.Level3.net (4.69.134.74) 76.265 ms
11 ae-82-82.ebr2.NewYork1.Level3.net (4.69.148.41) 76.820 ms
12 ae-2-2.ebr1.SanJose1.Level3.net (4.69.135.185) 149.101 ms
13 ae-91-91.csw4.SanJose1.Level3.net (4.69.153.14) 150.557 ms
14 ae-4-90.edge1.SanJose3.Level3.net (4.69.152.208) 162.022 ms
root@vserver:~#
All the ICMP "TTL exceeded" messages except the first and the
penultimate one in Level3 network have MPLS extensions
header(s24.postimg.org/4z9at9z45/ICMP_echo_reply_MPLS_extensions.png)
which is always the same except the tag value changes.
How does this technically work? What are the advantages of such setup?
thanks,
Martin
