BGP (Border Gateway Protocol) is the de facto path vector protocol used to excha
ID: 3792510 • Letter: B
Question
BGP (Border Gateway Protocol) is the de facto path vector protocol used to exchange routing
information on the Internet. Using a public route server (routeserver.org) in Germany, determine the
number of Autonomous Systems between that route server in Germany and Cal Poly Pomona. You'll
need to telnet to their route-server at route-server.ip.tiscali.net and run the command traceroute
www.cpp.edu. Examine the output and determine the following:
(a) How many autonomous systems are there to Cal Poly Pomona (AS 30679) from that route server in
Germany?
(b) Draw a diagram showing the path that trac might take, including Autonomous Systems, to get to
Cal Poly Pomona.
(c) Does the path vector protocol take in to account the number of "hops" from source to destination
when making a routing decision?
Explanation / Answer
rahul@ubuntu:~$ telnet route-server.ip.tiscali.net
Trying 213.200.64.94...
Connected to route-server.ip.tiscali.net.
Escape character is '^]'.
+--------------------------------------------------------------------+
| |
| GTT Route Monitor - AS3257 |
| |
| This system is solely for internet operational purposes. Any |
| misuse is strictly prohibited. All connections to this router |
| are logged. |
| |
| This server provides a view on the Tinet legacy routing table |
| that is used in Frankfurt/Germany. If you are interested in |
| other regions of the backbone check out http://www.as3257.net/ |
| |
| Please report problems to noc@gtt.net |
| |
+--------------------------------------------------------------------+
route-server.as3257.net>traceroute www.cpp.edu
Translating "www.cpp.edu"...domain server (213.200.90.90) (213.200.89.89)
Translating "www.cpp.edu"...domain server (213.200.90.90) [OK]
Type escape sequence to abort.
Tracing the route to www.cpp.edu (134.71.177.148)
1 xe-9-0-0-3.fra23.ip4.tinet.net (213.200.64.93) 0 msec 0 msec 0 msec
2 xe-2-1-0.fra44.ip4.tinet.net (213.200.82.13) 0 msec 0 msec
xe-1-2-0.cr4-fra4.ip4.gtt.net (141.136.111.62) [AS 3257] 0 msec
3 xe-10-2-0.edge5.frankfurt1.level3.net (4.68.63.57) [AS 3356] 4 msec 4 msec 0 msec
4 * * *
5 CENIC.ear1.LosAngeles1.Level3.net (4.35.156.66) [AS 3356] 152 msec 152 msec 152 msec
6 pom-csu--lax-agg6-10g.cenic.net (137.164.42.242) [AS 2152] 152 msec 152 msec 156 msec
7 br1-te-0-1-0--fw1-xe-1-0-1-0.csupomona.net (134.71.252.5) [AS 30679] 152 msec 156 msec 156 msec
8 fw1-xe-2-0-0-0--cr1-te-3-1.csupomona.net (134.71.252.75) [AS 30679] 152 msec 152 msec 156 msec
9 cr1-po99--drdc98-po3.csupomona.net (134.71.1.69) [AS 30679] 152 msec 152 msec 152 msec
The path taken is:
xe-9-0-0-3.fra23.ip4.tinet.net (213.200.64.93)
xe-1-2-0.cr4-fra4.ip4.gtt.net (141.136.111.62) [AS 3257]
xe-10-2-0.edge5.frankfurt1.level3.net (4.68.63.57) [AS 3356]
CENIC.ear1.LosAngeles1.Level3.net (4.35.156.66) [AS 3356]
pom-csu--lax-agg6-10g.cenic.net (137.164.42.242) [AS 2152]
br1-te-0-1-0--fw1-xe-1-0-1-0.csupomona.net (134.71.252.5) [AS 30679]
fw1-xe-2-0-0-0--cr1-te-3-1.csupomona.net (134.71.252.75) [AS 30679]
cr1-po99--drdc98-po3.csupomona.net (134.71.1.69) [AS 30679]
c) Yes, it takes into account the number of hops. Path vector routing uses Bellman Ford algorithm to determine loops.
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