Course: CEG3185 Professor: Jiying Zhao Semester: Winter 2015

Course:
Semester:
CEG3185
Winter 2015
Professor:
Room:
Phone:
Email:
Jiying Zhao
STE 5019
(613)562-5800 x 6667
jzhao@uottawa.ca
Assignment 4
Weight: 5%
Posted: March 25, 2015
Due: April 10, 2015, noon
1. [15 marks] Define the following parameters for a switching network:
N = number of hops between two given end systems
L = message length in bits
B = data rate, in bits per second (bps), on all links
P = fixed packet size, in bits
H = overhead (header), bits per packet
S = call setup time (circuits switching or virtual circuit) in seconds
R = call release time (circuits switching or virtual circuit) in seconds
D = propagation delay per hop in seconds
(a) For N=4, L=3200, B=9600, P=1024, H=16, S=0.2, D=0.001, compute the end-to-end delay for
circuit switching, virtual circuit packet switching, and datagram packet switching. Assume that
there are no acknowledgments. Ignore processing delay at nodes.
(b) Derive general expressions for the three techniques of part (a), taken two at a time (three
expressions in all), showing the conditions under which the delays are equal.
2. [5 marks] Although not explicitly stated, the Internet Protocol (IP) specification, RFC 791, defines the
minimum packet size at network technology must support to allow IP to run over it.
(a) Read Section 3.2 of RFC 791 to find out that value. What is it?
(b) Discuss the reason for adopting that specific value.
3. [10 marks] A 4480-byte IP datagram (with Identification of 07777H) is to be transmitted and needs to
be fragmented because it will pass through an Ethernet with a maximum payload of 1500 bytes.
Show the Identification, Total Length, More Flag, and Fragment Offset values in each of the resulting
fragments.
4. [10 marks] Refer to Frame 3. By fragmenting the carried IP datagram to two fragments with about
equal length, form two corresponding Ethernet-II frames.
Frame 3:
0000
0010
0020
0030
78
00
3b
ff
8d
30
61
ff
f7
2f
04
54
b0
f2
2a
f3
6d
40
13
00
72
00
88
00
00
80
33
02
1d
06
55
04
D:\data\zhao\2015w\ceg3185\assignment4_ceg3185_2015w.doc
09
91
aa
04
41
3a
51
ec
cc
c0
00
01
59
a8
00
01
08
00
00
04
00 45 00
11 3d 81
00 70 02
02
x...mr...A.Y..E.
.0/.@....:....=.
;a.*..3U.Q....p.
..T...........
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5. [15 marks] In the following figure, all the LANs, routers, bridge, and computers belong to one
company. The company has Class C addresses, 192.121.152.0. Help the company partition the
network into the needed number of sub-networks (allow as many computers as possible in each subnetwork), by identifying the subnet mask, assigning addresses to each of the sub-networks, assigning
needed IP addresses to routers and computers.
Station 1
LAN A
LAN B
Router 1
LAN C
Bridge 1
LAN D
Router 2
Station 2
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6. [15 marks] Compute RIP routing table for all the routers in the following figure. Then describe how an
IP datagram is routed from a computer on N5 to a computer on N2. In the figure, rectangles are used
to represent routers and clouds are used to represent networks.
N2
A
D
N1
N3
C
N5
F
B
E
N4
7. [15 marks] Apply Dijkstra’s algorithm to the following network to generate a shortest-path-tree for
node C and node D, and build a routing table for node C and node D.
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8. [15 marks] You are given the following internetworking scenario:
Router 1
A
143.24.56.1
a
c
b
155.23.76.12
Token Ring
155.23.77.254
143.24.56.254
Ethernet
Bridge
Ethernet
B
132.14.73.1
155.23.77.253
Ethernet
Router 2
c
155.23.76.25
b
a
Token Ring
132.14.73.156
The above IP network has just come on-line (i.e. all devices have just powered up). The routers
contain the following decision tables:
Network Subnetwork
132.14.0.0
143.24.56.0
155.23.76.0
155.23.77.0
Network Subnetwork
143.24.0.0
155.23.76.0
155.23.77.0
132.14.73.0
Router 1
Router Address
Network Mask
Interface
155.23.76.25
local
local
local
255.255.0.0
255.255.255.0
255.255.255.0
255.255.255.0
c
a
c
b
Router 2
Router Address
Network Mask
Interface
255.255.0.0
255.255.255.0
255.255.255.0
255.255.255.0
c
b
c
a
155.23.77.254
local
local
local
(a) List the actions and routing decisions taken by all stations and routers to route an IP datagram
containing an ICMP Echo Request transmitted by Station A to Station B.
(b) List the actions and routing decisions taken by all stations and routers to route an IP datagram
containing an ICMP Echo Reply returned by Station B to Station A.
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