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Current Wireless Systems: Cellular Network Architecture and Mobile IP

Learn about the architecture of UMTS cellular networks and the operation of Mobile IP, including agent discovery, registration, and tunneling. Explore the objectives, requirements, and applications of Mobile IP.

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Current Wireless Systems: Cellular Network Architecture and Mobile IP

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  1. ECE/CSC 575 – Section 1 Introduction to Wireless Networking Lecture 13Dr. 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) 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. FA Mobile IP Operation (2) Home network/ Subnet Correspondent Node (CN) HA Internet Backbone Agent advertisement 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 =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

  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 = 19 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 Registration request Registration reply Home network/ Subnet 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 Registration request Registration reply Home network/ Subnet Foreign Network/ Subnet Dr. Xinbing Wang

  10. Registration Process HA MN FA Beacon Signal 1 (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 Here is CoA or co-located CoA (C-CoA) for this MN 4 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 Data HA Encapsulation HA CoA/C-CoA Source To MN Payload Data Forwarding not through intermediate router if C-CoA used Forwarding through intermediate router if 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. HA 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 Packet to the CN routed Using standard IP routing Encapsulation FA Dr. Xinbing Wang

  14. Triangle Routing (2) • Pros • 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. HA 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 Update binding Packet to the CN routed Using standard IP routing FA Authorization & processing Dr. Xinbing Wang

  16. Optimized Routing (2) • Pros • 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. FA Mobile IPv6 Operation Home network/ Subnet CN do not know the MN’s CoA HA Internet Backbone CN knows the MN’s CoA Foreign Network/ Subnet Dr. Xinbing Wang

  21. Home Agent Registration • 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. 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 Dr. Xinbing Wang

  22. After Class • Reading materials • Chapter 12.1 • Exercise • 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

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