Here are the key points about how mobility support for both the correspondent and mobile host would affect end-to-end delays: - Datagrams would need to be tunneled through multiple home agents to reach the destination, adding additional encapsulation and forwarding hops. - The path taken by a datagram would become more indirect as it travels through multiple home agents rather than direct host-to-host routing. This increases propagation and transmission delays. - Additional processing is required at each home agent to encapsulate/decapsulate and forward the datagram, increasing processing delays. - If either the mobile host or correspondent changes locations, their registrations with home agents and mobility bindings need to be updated, introducing additional

1. Wireless&mobilenetworks
CC531: Advanced Networks
Computer Networking,
A top-down approach:Kurose – Ross (8th edition)

2. Introduction
 Types of wireless and mobile networks
A network that is wireless, but not mobile
A network that is mobile, but not wireless
A network that is both wireless and mobile
 Assumption:
Users are connected into larger network infrastructure by a wireless link at the
network’s edge.
• Wireless LANs as IEEE 802.11
• Cellular networks as 3G network

3. Introduction
 Elements of a wireless network:
1. Wireless hosts
End devices / end systems.
They run applications and initiate communication.
• Laptop
• Smartphone
• Desktop computer
Wireless hosts may or not be mobile.
network
infrastructure

4. Introduction
 Elements of a wireless network:
2. Wireless links:
A host connects to a base station through
wireless communication links.
Wireless links connect wireless hosts that
are located at the network’s edge.
Wireless links may also be used to connect
hosts within a network.
network
infrastructure

5. Introduction
 Elements of a wireless network:
2. Wireless links:
A host connects to a base station through
wireless communication links.
Wireless links connect wireless hosts that
are located at the network’s edge.
Wireless links may also be used to connect
hosts within a network.
network
infrastructure

6. Introduction
 Elements of a wireless network:
3. Base station:
It is the key part of the wireless network
infrastructure.
It has no counterpart in a wired network.
It is responsible for sending & receiving
data packets.
It is responsible for coordinating the
transmission of multiple wireless hosts.
network
infrastructure

7. Introduction
 Elements of a wireless network:
 Hosts mode of operation:
a) Infrastructure mode:
 Base station connects mobiles into wired network
 handoff: mobile changes base station providing connection
into wired network
b) Ad-hoc mode:
 no base stations
 nodes can only transmit to other nodes within link coverage
network
infrastructure

8. Introduction
 Categories of wireless networks
1. Single-hop, infrastructure based:
 These networks has a single base station that is connected to the internet.
• IEEE 802.11 network in a classroom
 All data transmissions are one hop away from the base station.
2. Single-hop, infrastructure-less:
 IEEE 802.11networks in ad-hoc mode
 Bluetooth devices

9. Introduction
 Categories of wireless networks
3. Multi-hop, infrastructure based:
 Base station, located in a wireless network, is connected to a larger wired network.
 Data communications may be done through several relays.
• Wireless mesh network
4. Multi-hop, infrastructure-less:
 Many nodes may be used to relay data until it reaches destination
 Nodes may be mobile
• MANETs ( Mobile Ad-hoc Networks)
• VANETs (Vehicular Ad-hoc Networks)

10. Wireless links & Network
characteristics
 Important differences between wired links & wireless links:
1. Decreasing signal strength:
 Radio signals attenuates as it passes through matter.
 In space, electro-magnetic radiations disperse as the distance between the sender and receiver
increases (path-loss)
2. Interference from all sources:
 Radio signals of the same frequencies will interfere with each other.
• 2.4 GHZ wireless phones & 802.11 b wireless LAN
3. Multipath propagation:
 It occurs when a portion of the electromagnetic waves reflect-off objects, it take paths of different
lengths between the sender and receiver.

11. Wireless links & Network
characteristics
 Signal to noise ratio (SNR):
 It is the relative measure of the strength of the received signal and the noise.
 SNR is measured in dB.
 Large SNR makes it easier to extract the transmitted signal from the background noise.
 Bit error rate (BER):
 It is the probability that a transmitted bit is received in error at the receiver.
The higher SNR, the lower BER
 Sender can increase SNR by increasing the transmission power, sender can decrease the probability
that a frame is received in error by increasing the transmission power.

12. Wireless links & Network
characteristics
 Hidden terminal problem:
 A physical obstruction is preventing A & C from hearing
each other.
 However, their transmissions are interfering with each
other.
 In one scenario, Station A can communicate with Station
B. Station C can also communicate with Access Point
Station B.
 However, Stations A and C cannot communicate with each
other as they are out of range of each other, and thus start
to transmit simultaneously preventing B from receiving
messages intended for it.
A
B
C

13. Wireless links & Network
characteristics
 Fading / signal attenuation problem:
 An undetectable collision at the receiver that may result
from fading of the signal’s strength in the wireless
medium.
 Both A & C are placed at a distance where they can’t
detect each other’s signal transmission.
 However, their signals are not string enough to interfere.
A B C
A’s signal
strength
space
C’s signal
strength

14. Wireless links & Network
characteristics
 Managing multiple access is more complex in a wireless network.
 Categories / classes of medium access protocols:
 Channel partitioning
• This method divides the channels into smaller pieces (time slots, frequencies, code)
 Random access
• This method make use of the whole channel without any division, which allows collisions.
• Random access must implement collision recovery mechanisms.
 Taking turns
• Nodes take turns in accessing the channel.
• Nodes with more to send take longer turns.

15. Question 1
 What is meant by a mobile IP?

16. Question 1
 What is meant by a mobile IP?
 It is a communication protocol that is designed to allow mobile device users to move from one network
to another while maintaining a permanent IP address.

17. Question 2
 Explain the function of the following entities:
Mobile Node (MN)
Home Agent (HA)
Home Address
Home Network
Foreign Network
Foreign Agent (FA)
Care of address (COA)
Mobility Binding
Correspondent node (CN)

18. Question 2
 Explain the function of the following entities:
 Mobile Node (MN)
 a node moving to different network, with permanent home address.
 Home Agent (HA)
a router on a mobile node’s home network which tunnels datagrams for delivery to the mobile
when it is away from home, and maintains current location information for the mobile node.
Home Address
the static fixed IP address allocated to a
mobile node by home agent.
Home Network
 a network, having a network IP matching
that of a mobile node’s home address.

19. Question 2
 Explain the function of the following entities:
 Foreign Network
a network other than a mobile node’s home network.
 Foreign Agent (FA)
router in foreign network that provides COA and tunneling with home agent and forward the
packets to MN.
Care of address (COA)
termination point of a tunnel toward a MN in the
foreign network.
Mobility Binding
the association of a home address with a care of
address.
Correspondent node (CN)
 a peer node with which a mobile node is communicating.

20. Question 3
 Discuss the different phases in Mobile IP.

21. Question 3
 Discuss the different phases in Mobile IP.
Agent discovery: Mobile IP defines the protocols used by a home or foreign agent to
advertise its services to mobile nodes, and protocols for mobile nodes to solicit the
services of a foreign or home agent
Registration: Mobile IP defines the protocols used by the mobile node and/or foreign
agent to register and deregister COAs with a mobile node’s home agent.
Data transfer: the manner in which datagrams are forwarded to mobile nodes by a
home agent, including rules for forwarding datagrams, rules for handling error
conditions, and several forms of encapsulation

22. Question 3
 Discuss the different phases in Mobile IP.

23. Question 4
 Consider two mobile nodes in a foreign network having a foreign agent. Is it possible for the two mobile
nodes to use the same care-of address in mobile IP? Explain your answer.

24. Question 4
 Consider two mobile nodes in a foreign network having a foreign agent. Is it possible for the two mobile
nodes to use the same care-of address in mobile IP? Explain your answer.
Two mobiles could certainly have the same care-of-address in the same visited network. Indeed, if the care-
of-address is the address of the foreign agent, then this address would be the same.
Once the foreign agent decapsulates the tunneled datagram and determines the address of the mobile, then
separate addresses would need to be used to send the datagrams separately to their different destinations
(mobiles) within the visited network.

25. Question 5
 Suppose the correspondent in Figure 6.22 were mobile. Sketch the additional network-layer infrastructure
that would be needed to route the datagram from the original mobile user to the (now mobile)
correspondent. Show the structure of the datagram(s) between the original mobile user and the (now
mobile) correspondent, as in Figure 6.23.

26. Question 5
 Solution

27. Question 6
 How would mobility support for both hosts (the correspondent and the mobile) affect end-to-end delays
of datagrams between the source and the destination?

28. Question 6
 How would mobility support for both hosts (the correspondent and the mobile) affect end-to-end delays
of datagrams between the source and the destination?
Because datagrams must be first forward to the home agent, and from there to the mobile node, the delays
will generally be longer than via direct routing.
Note that it is possible, however, that the direct delay from the correspondent to the mobile (i.e., if the
datagram is not routed through the home agent) could actually be smaller than the sum of the delay from
the correspondent to the home agent and from there to the mobile. It would depend on the delays on these
various path segments.
Note that indirect routing also adds a home agent processing (e.g., encapsulation) delay.

29. Question 7
 How would mobility support for both hosts (the correspondent and the mobile) affect end-to-end delays
of datagrams between the source and the destination?