Assignment
Date: 9/20/2004
Due Day:
9/29/2004
Description:
Part 1. End System and Router Configuration
on a Simple UML-based Virtual Network
Exercise 1. Start up UML-bases Virtual Machines on a MS Virtual PC (VPC) 2004-based Fedora Core Virtual Machine
edit /etc/rc.d/rc.inet1.conf
replace IPADDR[0]="172.31.0.174"
(instead of 172.31.0.169)
replace IPADDR[1]="10.0.2.174" (instead of 10.0.0.169)
Exercise 2. Using route command to configure routing tables for allowing packets from lamb to be routed by b2b to bilbo.
therefore
ICMP echo request has been sent 5 times but no ICMP echo reply
return.
Let us check if the b2b receives the ICMP echo request packets with
tcpdump
-i eth1
and rerun the ping -c 5 10.0.1.159 on Lamb.
we got the following packets captured on eth1 of b2b:
04:51:23.662218 10.0.0.169 > 10.0.1.159: icmp: echo request (DF)
04:51:25.221724 10.0.0.169 > 10.0.1.159: icmp: echo request (DF)
04:51:27.704457 10.0.0.169 > 10.0.1.159: icmp: echo request (DF)
Therefore the packets was received by b2b at eth1.
We then run tcpdump -i eth2 and repeat the ping from lamb.
We did not see any message appear on eth2 of b2b.
Therefore packets are not forwarded from eth1 to eth2 of b2b.
D3. Based on the ping result, does b2b receives the packets destined for
10.0.1.159?
Ans: Yes. But does not forward it from eth1 to eth2.
Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 10.0.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth2 172.31.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo 0.0.0.0 172.31.0.101 0.0.0.0 UG 0 0 0 eth0
So
if we did not turn down eth0, then there is a default route using eth0 with
gw=172.31.0.101.
The ICMP echo reply to return through eth0 and never reach lamb!
Destination Gateway Genmask Flags MSS Window irtt Iface 10.0.0.0 10.0.2.172 255.255.255.0 U 0 0 0 eth1 10.0.1.0 10.0.2.172 255.255.255.0 U 0 0 0 eth1On lamb, run the following route command
Destination Gateway Genmask Flags MSS Window irtt Iface 10.0.2.0 10.0.0.172 255.255.255.0 U 0 0 0 eth1On bilbo, run the following route command
Destination Gateway Genmask Flags MSS Window irtt Iface 10.0.2.0 10.0.0.172 255.255.255.0 U 0 0 0 eth2
or you can make b2b as the default gateway of Lamb, bilbo, and frodo by entering
the following commands:
On
frodo, route add default gw 10.0.2.172
On bilbo, route add default gw 10.0.1.172
On lamb, route add default gw 10.0.0.172
Part 2.
Exercise 1. Reachability Analysis
Note you can use a tool called setool to verify your reachability analysis result. The web page for using setool is at http://cs.uccs.edu/~cs522/hw/hwF2004/setool.htm
Exercise 2. Understand the protocol behavior of Alternating Bit Protocol.
1. (1, 1, E, E)S:New Dataà(2, 1, E, E)
2. (2,
1, E, E)S:-D0à(3,
1, D0, E)
3. (3, 1, D0, E) R: +D0à(3,
2, E, E)
4. (3, 2, E, E)R: Deliver Dataà(3,
3, E, E)
5. (3, 3, E, E)R:-A0à(3,
4, E, A0)
6. (3, 4, E, A0)A:+A0à(4, 4, E, E)
7. (4, 4, E, E)S:New Dataà(5, 4, E, E)
8. (5, 4, E, E)S:-D1à(6, 4, D1, E)
9. (6, 4, D1, E) C1:Second Msg, loses D1à(6, 4, E, E)
10. (6, 4, E, E)S:timeoutà(8, 4, E, E)
11. (8, 4, E, E)S:-D1à(6, 4, D1, E) # this is a retransmission of D1
12. (6, 4, D1, E)R: +D1à(6, 5, E, E) # 3rd msg on C1, C1delivers D1
13. (6, 5, E, E)R:Deliver Dataà(6, 6, E, E)
14.
(6, 6, E, E)R:-A1à(6,
1, E, A1)
15. (6, 1, E, A1)C2: Second Msg, Lose A1à(6,
1, E, E)
16. (6, 1, E, E)S:timeoutà(8,
1, E, E)
17. (8, 1, E, E)S:-D1à(6,
1, D1, E)
18. (6, 1, D1, E)C1:4th Msg, loses D1à(6, 1, E, E)
19. (6,
1, E, E)S:timeoutà(8,
1, E, E)
20. (8, 1, E, E)S:-D1à(6,
1, D1, E)
21. (6, 1, D1, E)R:+D1à(6,
8, E, E) # 5th msg on C1, C1 delivers D1
22. (6, 8, E, E)R:-A1à(6,
1, E, A1) # retransmission of A1
23.
(6, 1, E, A1)S:+A1à(1,
1, E, E) # This completes the first cycle of Senser's CFSM.
Create your solution as hw3.html
Email me the url of the hw3.html to chow@cs.uccs.edu