Unit iii - mobile ip and wireless access protocol
- 1. UNIT-III MOBILE IP AND WIRELESS ACCESS PROTOCOL
- 2. MOBILE IP • The term mobile in this context implies that a user is connected to one or more applications across the Internet, that the user's point of attachment changes dynamically, and that all connections are automatically maintained despite the change. • Routers make use of the IP address in an IP datagram to perform routing. • In particular, the network portion of an IP address is used by routers to move a datagram from the source computer to the network to which the target computer is attached. • Then the final router on the path, which is attached to the same network as the target computer, uses the host portion of the IP address to deliver the IP datagram to the destination. Operation of Mobile IP
- 3. • A mobile node is assigned to a particular network, known as its home network. Its IP address on that network, known as its home address, is static. • When the mobile node moves its attachment point to another network, that network is considered a foreign network for this host. • Once the mobile node is reattached, it makes its presence known by registering with a network node, typically a router, on the foreign network known as a foreign agent. • The mobile node then communicates with a similar agent on the user's home network, known as a home agent, giving the home agent the care-of address of the mobile node.
- 5. • To support the operations Mobile IP includes three basic capabilities: • Discovery: A mobile node uses a discovery procedure to identify prospective home agents and foreign agents. • Registration: A mobile node uses an authenticated registration procedure to inform its home agent of its care-of address. • Tunneling: Tunneling is used to forward IP datagrams from a home address to a care-of address.
- 6. Discovery • The discovery process in Mobile IP is very similar to the router advertisement process defined in ICMP (Internet Control Message Protocol). Accordingly, agent discovery makes use of ICMP router advertisement messages, with one or more extensions specific to Mobile IP. Protocol Support for Mobile IP
- 7. • The router advertisement portion of the message includes the IP address of the router. • The advertisement extension includes additional information about the router's role as an agent. • A mobile node listens for these agent advertisement messages. Mobile IP Agent Advertisement Message
- 8. • The agent advertisement extension follows the ICMP router advertisement fields and consists of the following fields. • • Type: 16, indicates that this is an agent advertisement. • • Length: Number of bytes in the extension, excluding the Type and Length fields. • • Sequence Number: The count of agent advertisement messages sent since the agent was initialized. • • Lifetime: The longest lifetime, in seconds, that this agent is willing to accept a registration request from a mobile node. • • R: Registration with this foreign agent is required. Even those mobile nodes that have already acquired a care-of address from this foreign agent must re-register. • B: Busy. The foreign agent will not accept registrations from additional mobile nodes. • • H: This agent offers services as a home agent on this network. • • F: This agent offers services as a foreign agent on this network.
- 9. • • M: This agent can receive tunneled IP datagrams that use minimal encapsulation • • G: This agent can receive tunneled IP datagrams that use GRE encapsulation. • • r: reserved. • • T: Foreign agent supports reverse tunneling. • • Care-Of Address: The care-of address or addresses supported by this agent on this network. • The registration process involves four steps: • 1. The mobile node requests the forwarding service by sending a registration request to the foreign agent. • 2. The foreign agent relays this request to the mobile node's home agent. • 3. The home agent either accepts or denies the request and sends a registration reply to the foreign agent. • 4. The foreign agent relays this reply to the mobile node. Registration
- 10. Mobile IP Registration Messages
- 11. Tunneling • Once a mobile node is registered with a home agent, the home agent must be able to intercept IP datagrams sent to the mobile node's home address so that these datagrams can be forwarded via tunneling. • The standard does not mandate a specific technique for this purpose but references ARP (Address Resolution Protocol) as a possible mechanism.
- 12. WIRELESS APPLICATION PROTOCOL • The Wireless Application Protocol (WAP) is a universal, open standard developed by the WAP Forum to provide mobile users of wireless phones and other wireless terminals . • WAP is designed to work with all wireless network technologies (e.g., GSM, CDMA, and TDMA). • The WAP specification includes • • A programming model based on the WWW Programming model • A markup language, the Wireless Markup Language, adhering to XML • A specification of a small browser suitable for a mobile, wireless terminal • A lightweight communications protocol stack • • A framework for wireless telephony applications (WTAs)
- 15. Wireless Markup Language • WML was designed to describe content and format for presenting data on devices with limited bandwidth, limited screen size, and limited user input capability. • It is designed to work with telephone keypads, styluses, and other input devices common to mobile, wireless communication. • Text and image support: Formatting and layout commands are provided for text and limited image capability. • Support for navigation among cards and decks: WML includes provisions for event handling, which is used for navigation or executing scripts.
- 16. WML Script • WML Script is a scripting language with similarities to JavaScript. • It is designed for defining script-type programs in a user device with limited processing power and memory.
- 17. WML Tags
- 19. Wireless Session Protocol • WSP provides applications with an interface for two session services. • The connection oriented session service operates above the reliable transport protocol WTP, and the connectionless session service operates above the unreliable transport protocol WDP. • WSP Service In general, a connection-mode WSP provides the following services: • Establish a reliable session from client to server and release that session in an orderly manner. • Agree on a common level of protocol functionality using capability negotiation. • Exchange content between client and server using compact encoding.
- 20. • Suspend and resume a session. • Push content from server to client. • Session establishment • Server address: The peer with which the session is to be established. • Client address: The originator of the session. • Client headers: Contain attribute information that can be used for application level parameters to be communicated to the peer.
- 21. Wireless Transaction Protocol • WTP manages transactions by conveying requests and responses between a user agent (such as a WAP browser) and an application server for such activities as browsing and e-transactions. • WTP includes the following features: • Three classes of transaction service. • Optional user-to-user reliability: WTP user triggers the confirmation of each received message. • Optional out-of-band data on acknowledgments. • Asynchronous transactions.
- 22. WTP Transaction Classes • WTP provides three transaction classes that may be invoked by WSP or another higher layer protocol: • Class 0: Unreliable invoke message with no result message • Class 1: Reliable invoke message with no result message • Class 2: Unreliable invoke message with one reliable result message
- 24. Wireless Datagram Protocol • WDP is used to adapt a higher-layer WAP protocol to the communication mechanism (called the bearer) used between the mobile node and the WAP gateway. • service with the following parameters: • • Source address: Address of the device making a request to the WDP layer • • Source port: Application address associated with the source address • • Destination address: Destination address for the data submitted to WDP • • Destination port: Application address associated with the destination address • • User data: User data from the next higher layer, submitted to WDP for transmission to the destination port
- 25. • The following fields are necessary in a WDP PDU: • • Header length (1 byte): Length of header. • • Port numbers identifier (1 byte) • • Port numbers length (1 byte) • • Destination port (2 bytes) • • Source port (2 bytes) • SAR identifier (1 byte) • SAR length (1 byte) • Datagram reference number (1 bytes) • Number of segments (1 byte) • Segment count • User data (1 to n bytes)