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

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

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

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

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

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 =4 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 = 255.255.255.255 (broadcast) or 224.0.0.2 (multicast) Type = 10 Code = 10 Checksum Reserved 4 bytes (32 bits) Dr. Xinbing Wang

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 = 19 Length Prefix-length [1] Prefix-length [2] (Optional) 4 bytes (32 bits) Dr. Xinbing Wang

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

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

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

Message Forwarding Incoming message for MN Source To MN Payload Data HA 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

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

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

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

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

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

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

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

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

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

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

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