1. Introduction to Wireless Networking
ECE/CSC 575 – Section 1
Introduction to Wireless Networking
Lecture 13 Dr. Xinbing Wang

2. Part 3: Current Wireless Systems
Cellular network architecture: UMTS (Chapter 10)
Mobile IP (Chapter 12)
Objectives and requirements of Mobile IP
Mobile IP operation: advertisement, registration, and tunneling.
Triangle routing and optimized routing
Mobile IPv6
Open question: where will mobile IP be used?
Labs: registration, handoff, and authentication
Wireless LAN (Chapters 11/13/14)
In our daily lives, wireless communication technology is used everywhere, from VCR remote control, to satellite weather forecast. The common characteristics of wireless communication systems is that there is no physical (visible) lines between two communication parties.
Therefore, a wireless system is able to support user roaming. For example, we do not have to use a remote control in a particular position to.., we can use our cellular phones almost everywhere.
However, there are many impairments to a wireless channel, causing a lot of limitations to wireless communications system such as geographical.. (signal fading, additional noise, cochannel interference. Wireless systems also suffers from limit usable spectral width, so that the transmission rate is relatively low.
Specifically, wireless cellular systems based on radio propagation has been evolving from narrow band (1G, late 170s) to wide-band(3G).
With their geographical coverage limitation, wireless systems need a backbone network to extend their geographical coverage to enable global communications.
The interoworking of a wireless network as the front-end and the Internet as the backbone has received much attention in recent years.
So we will first take a look at the network architecture of current wireless systems,…, Then we will talk about the evolution from 2G to 3G systems.
Dr. Xinbing Wang

3. Mobile IP Operation
Home subnet prefix: the IP subnet prefix corresponding to an MN’s home address.
Foreign subnet prefix: the IP subnet prefix other than the MN’s home subnet prefix.
address B
Subnet prefix B
Internet Backbone
address B
& address C
Subnet prefix C
A node moves from a link with the prefix B to a link eith the prefix C. On link C the node gets an additional address which has the prefix of this link.
Dr. Xinbing Wang

4. Mobile IP Operation (2) HA Agent advertisement FA FA Home network/
Subnet
Correspondent
Node (CN) HA
Internet Backbone
Agent advertisement FA FA
Foreign Network/
Subnet 2
Foreign Network/
Subnet 1
Dr. Xinbing Wang

5. Three Processes
Agent Discovery: an MN determines its new attachment point or IP address through agent advertisements.
Determine to which link it is connected
Detect if it has changed its point of attachment
Obtain a CoA if it is connected to a foreign link
Allowed to send agent solicitation requests to agent
Agent discovery messages are carried by the ICMP packets.
Registration: an MN requests service from an FA and inform its HA of a new CoA.
Involve registration and deregistration with its HA
Registration message is carried by the UDP packets.
Tunneling (routing): Mobile IP tunnels datagram to the MN, whether it is away from its home network or not.
Encapsulation at the entering point of a tunnel
Decapsulation at the exit point of a tunnel
Dr. Xinbing Wang

6. Agent Discovery Agent solicitation message
Identical to ICMP router solicitations, except having IP time to Live field set to 1.
When an HA or FA receives one, it should immediately respond by transmitting an Agent Advertisement .
Vers = Type of service Total length
Identification Flags Fragment Offset
Time to Live = 1 Protocol = ICMP header Checksum
Source Address = Mobile node’s home address
Desti Addr = (broadcast) or (multicast)
Type = 10 Code = 10 Checksum
Reserved
4 bytes (32 bits)
Dr. Xinbing Wang

7. Agent Discovery (2) Agent advertisement messages
They are formed by appending one or more of the extensions defined by Mobile IP to the ICMP router advertisement message (RFC 1256).
The mobility agent advertisement extension must be included by agents.
IP Header (RFC 791)
20 bytes
ICMP Router Advertisement (RFC 1256)
Type = 16 Length Sequence number
(maximum) registration lifetime Reserved
Mobility agent
Advertisement
Extension
(RFC 2002)
Care of Address (1)….
Type = Length Prefix-length [1] Prefix-length [2]
(Optional)
4 bytes (32 bits)
Dr. Xinbing Wang

8. Registration and Deregistration
When an MN moves to a visiting location, it needs to register with its HA. When it returns to its home network, it also needs to deregister with its HA to update its current CoA (home address).
Registration with care-of-address
Internet Backbone HA FA
Home network/
Subnet
Registration request
Registration reply
Foreign Network/
Subnet
Dr. Xinbing Wang

9. Registration and Deregistration (2)
Registration with care-of-address
Registration with colocated care-of-address: an IP address that represents the current position of the MN on the foreign network and can be used by only one MN at a time.
Deregistration with the HA
Internet Backbone HA FA
Home network/
Subnet
Registration request
Registration reply
Foreign Network/
Subnet
Dr. Xinbing Wang

10. Registration Process HA MN FA 1 Beacon Signal (Any one new) 1’
I am new here 1”
OK, send information 2
Here is my HA and binding infomation.
CoA or C-CoA created 3 4
Here is CoA or co-located CoA (C-CoA) for this MN 4’
Same as step 4 4”
Same as step 4
Acknowledge Registration + binding
Dr. Xinbing Wang

11. Message Forwarding Incoming message for MN Source To MN Payload DataHA
Encapsulation
HA CoA/C-CoA
Source
To MN
Payload Data
Forwarding through intermediate router if CoA used
Forwarding not through intermediate router if C-CoA used FA
Decapsulation
Source
To MN
Payload Data MN
Decapsulation done at MN
Dr. Xinbing Wang

12. Tunneling and Routing
Tunneling is a process in which the HA encapsulates the message from the IP host for delivery to the MN via its FA.
Binding: the association of the home address of an MN with a CoA for that MN, along with the remaining lifetime of that association.
Two routing schemes:
Triangle routing
Optimized routing
Dr. Xinbing Wang

13. Triangle Routing
A datagram is sent from the CN to the MN’s HA through IP.
The HA intercepts the datagram and tunnels the datagram to the MN’s CoA.
At the FA, the datagram is decapsultated and delivered to the MN.
For datagram sent by the MN, standard IP routing is used to deliver each datagram to the destination.
Packet from the CN routed
indirectly through the HA CN
Internet Backbone HA
Packet to the CN routed
Using standard IP routing
Encapsulation FA
Dr. Xinbing Wang

14. Triangle Routing (2) Pros Cons Simple
The number of control messages is limited
No extra binding messages are needed
Cons
The HA is a “centralized” point to delivery every packet, even though there exists a short-cut between the CN and the FA. This may result in high end-to-end delay.
The HA is a potential bottleneck because it can easily be overloaded.
When the MN moves further and further, registration cost can be very large.
Dr. Xinbing Wang

15. Optimized Routing The MN informs the CN of its CoA address
The CN can tunnel the packets directly to the MN by bypassing the HA.
Every traffic resource is allowed to cache and use binding copies.
Packet from the CN routed
indirectly through the HA CN
Internet Backbone HA
Update
binding
Packet to the CN routed
Using standard IP routing FA
Authorization &
processing
Dr. Xinbing Wang

16. Optimized Routing (2) Pros Cons
With the cache and binding copies, packets can be delivered directly to the MNs, thus providing better QoS.
For high mobility users, the previous FA can forward packets to the MN’s new CoA.
Cons
Very complex
Overhead of messages and processing (cache inquiries and bindings) may be large.
Security issue: each CN must be able to authorized every FA that the MN is connected.
Dr. Xinbing Wang

17. Mobile IPv6
Based on IPv6, using IP routing header, authentication header, and route optimization.
There is NO foreign agent. The MN obtains a colocated care-of-address on a foreign link, and reports to its HA.
One MN may have multiple care-of-addresses.
The security functions are mandatory instead of optional.
Binding: The association of the home address of an MN with a care-of-address that MN, along with the remaining lifetime of that association.
Dr. Xinbing Wang

18. Mobile IPv6 messages
Mobile IPv6 requires the exchange of additional information. All new messages used in mobile IPv6 are defined as IPv6 destination options.
Binding Update: an MN informs its HA or any other CNs about its current CoA. Any packet including a Binding Update must also include an AH or ESP header.
Binding Acknowledgement: to acknowledge the receipt of a Binding Update, if an ACK was requested, it must also include an AH or ESP header.
Binding Request: for any node to request an MN to send a Binding Update with the current CoA.
Home Address : used in a packet sent by an MN to inform the receiver of this packet about the MN’s home address. This message must also be covered by the authentication.
Dr. Xinbing Wang

19. Data Structures
Binding Cache: Every IPv6 node has a Binding Cache which is used to hold the bindings for other nodes. If a node receives a Binding Update, it will add this binding to its Binding Cache.
Binding Update List: Every MN has a Binding Update List which is used to store information about each Binding Update sent by this MN for which the lifetime has not expired. It contains all Binding Updates sent to any CNs and to its HA.
Home Agent List: Each HA generates a list, which contains information about other HAs on a home link.
Dr. Xinbing Wang

20. Mobile IPv6 Operation HA FA Home network/ Subnet CN do not know
the MN’s CoA HA
Internet Backbone
CN knows the
MN’s CoA FA
Foreign Network/
Subnet
Dr. Xinbing Wang

21. Home Agent Registration
The MN sends a Binding Update to the HA
Internet Backbone HA FA
Home network/
Subnet
Foreign Network/
Subnet
The HA accepts the Binding Update and
returns a Binding Acknowledgement
Route Optimization: To avoid triangle routing, an MN can send Binding Update to any CN. This allows IPv6 nodes to cache the current CoA address and send packets directly to an MN.
Dr. Xinbing Wang

22. After Class Reading materials Exercise Chapter 12.1 What is tunneling?
How can Mobile IP detects mobile users?
What is Mobile IP registration?
What are home agent, mobile agent, foreign agent?
Difference between Mobile IP and Mobile IPv6
Dr. Xinbing Wang