Network Layer; Location Management; Mobile IP Y. Richard Yang 2/17/2009

2 Recap: Wireless Link Layer r The basic services of the link layer m framing, link reliability, etc m link access interference, hidden terminal quality of service (and fairness) control

3 Distributed Sharing of Unlicensed Spectrum r Utilization of allocated spectrum is sow r Federal Communications Committee (FCC) is increasing unlicensed spectrum allocation: m Industry, Science, and Medicine (ISM) m Unlicensed Personal Communication Service (UPCS): MHz and MHz (30 Mhz) m National Information Infrastructure (NII) Band: 350 Mhz m Ghz Millermeter Wave band r Cross-protocol spectrum sharing is difficult

4 One Proposal for UPCS Spectrum Etiquette r Upper bound on energy level [official] r A station must “Listen Before Talk” (LBT) [official] m be quite for a monitoring time M after the previous energy level stops r Penalty for using a channel [non-official] m if a station holds a channel for a duration H, the station cannot transmit for P(H) amount of time as a penalty Question: what property do you want P(H) to hold?

5 How to Design P(H)? r Assume an arrived bit of a user is transmitted immediately if the user is having the channel; otherwise the bit has to wait until the next interval r What is the average delay MHP(H)H

6 Discussion r Spectrum sharing is largely still an open field r There are several proposals and evaluations, e.g., m m r A potential term project topic

7 Recap: Wireless Link Layer r The basic services of the link layer m link access interference, hidden terminal quality of service (and fairness) control m framing, link reliability, etc r Guided by network layer m transmit to which neighbor at what quality B A S E F H J D C G I K M N L

8 Network Layer Services r Transport packets from source to dest r Network layer protocol in every host, router Basic functions: r Control plane m compute routing from sources to destinations r Data plane: forwarding m move packets from input interface to appropriate output interface(s) B A S1S1 E D2D2 S2S2 J D1D1 C G I K M N L

9 Network Layer: API r API (provided to upper layer) m transmit( info, src, dest, …); r A key decision in network layer design is how to represent destinations? m we refer to how applications specify destinations as the addressing scheme m the supported addressing scheme(s) can have profound impacts on usability, flexibility, and scalability

Discussion: How to Specify a Destination? 10 B A S E F H J D C G I K M N L

Two Basic Approaches for Identifying Destinations r Locators m encode locations on network topology r Identifiers (ID) m independent of network topology 11 A E D CB F

Addressing Scheme: Sensornet Example r Destination: message to a sensor (e.g., who detected fire) m 12 B A S E D F J D C G I K M N L

13 Addressing Scheme: Telephone r Very first scheme: connection by operators to business m ID or locator? r The telephone numbering scheme: m invented in 1888 by Almon Strowger, an undertaker : “No longer will my competitor steal all my business just because his wife is a BELL operator.”

Telephone Addressing Scheme r E.164: Maximum 15 digits r Hierarchical addressing scheme: country code + national destination code (optional) + subscriber number) m e.g., r Why hierarchical addressing scheme? m uniquely determines the switch upon which the telephone is attached to r Issues of such a scheme? 14 B A S E D F J D C G I K M N L

Addressing Scheme: Internet r How to specify the destination which is the color printer on the 4 th floor of AKW m Internet domain name: lw4c.cs.yale.edu m Internet protocol (IP) address: m [building = AKW; floor=4; entity = printer; quality = color] 15

16 Addressing Scheme: IP r IP address: 32-bit identifier for an interface r An IP address is associated with an interface %/sbin/ifconfig -a =

17 IP Addressing r Hierarchical scheme: m network part (high order bits) m host part (low order bits) r What’s a network? ( from IP address perspective) m device interfaces with same network part of IP address m link layer can reach each other

18 Why Hierarchy? r The hierarchy is important for the scalability of Internet routing r The routing system handles only the number of networks m 275,280 networks on Jan ; m 625 mil hosts in Jan. 2009)

19 Routing in IP/Telephone Networks r Represent network as a graph r Determine a path to each destination on the graph m Q: what does a node in the graph represent? A E D CB F

20 Key Problems r Location management m due to user mobility (roaming), hierarchical routing (address aggregation) may cause user devices to be not attached to their networks/switches need forwarding/location management r Dynamic routing m due to node mobility/wireless connectivity, link connectivity/quality can be highly dynamic need to design routing protocols that are effective in handling dynamic topologies r Broadcast wireless m there can be interference among links and paths ( need good link performance metrics or scheduling) A E D CB F

Outline r Admin. r Network addressing schemes r Location management in cellular networks 21

22 Routing in Cellular Networks r Cellular networks face the location management problem: m a phone may be out of its home switch r How GSM handles out-of-switch phones: m a global home location register (HLR) database for each carrier m each base transceiver station (BTS) has a visitor location register (VLR) A E D CB F

23 BSC Radio Subsystem BSC GSM MS (mobile station) BSC (base station controller) BTS (base transceiver station) MSC (mobile switching center) GMSC (gateway MSC) fixed network MSC GMSC Network & Switching Subsystem and Operation Subsystem MS BTS VLR HLR

24 Two Primitives for Cellular Location Management r Mobile station: reports to the network of the cell it is in m called update m uses the uplink channel r Network: queries different cells to locate a mobile station m called paging m uses the downlink channel

25 Performance of the Two Primitives r A city with 3M users r During busy hour (11 am - noon) r Assume each paging message is 100 bits r Update only m update messages: millions m Q: why so many update messages? r Paging only m paging traffic: 1433 calls/sec m Q: bw? arrival rate?

26 Location Management Through Location Areas (LA) r A hybrid of paging and update r Used in the current cellular networks such as GSM r Partitions the cells into location areas (LA) m e.g., around 10 cells in diameter in current systems r Each cell (BTS) periodically announces its LA id r If a mobile station arrives at a new location area, it updates the base station about its presence r When locating a MS, the network pages the cells in an LA

27 How to Decide the LAs: A Simple Model r Assume the cells are given  Cell i has on average N i users in it during one unit time; each user receives c calls per unit time  There are N ij users move from cell i to cell j in a unit of time Cell 1 Cell 2 N1N1 N2N2 N 12 N 21

28 How to Decide the LAs: A Simple Scenario r Separate LAs for cells 1 and 2 m update cost: N 12 + N 21 m paging cost: c (N 1 + N 2 ) r Merge cells 1 and 2 into a single LA m update cost: 0 m paging cost: 2 c (N 1 + N 2 ) r When to merge and when to separate? Cell 1 Cell 2 N1N1 N2N2 N 12 N 21

29 Discussions r The LA design should consider m call pattern: when (how often) does a mobile station receive a call? m mobility model: how does a mobile station move? r How to further improve the performance of location management?

30 Dynamic/Distributed Location Management Schemes r In dynamic/distributed location management schemes, each user makes independent decision about when to update

31 Dynamic/Distributed Location Management Schemes r Timer based A MS sends an update after some given time T r Movement based A MS sends an update after it has visited N different cells r Distance based A MS sends an update after it has moved away for D distance (need ability to measure distance) r Profile based A MS predicts its mobility model and updates the network when necessary

32 Timer-based Location Management  A MS sends an update after some given timer T r The network pages the MS upon a call request at all cells which the MS can potentially arrive during T m cells reachable from last update cell, e.g., within distance v max * T, where v max is the maximum speed r Question: how to determine T?

33 Timer-based Location Management r Assume time between call arrivals is T call r Cell radius is d cell r Total bandwidth cost: Take derivative and set it to 0 to derive the optimal value:

34 Summary: Location Management r Two primitives of location management in cellular networks m update (a proactive approach) m paging (a reactive approach) r The location area (LA) approach m a hybrid approach r Distributed approaches m timer based m movement based m distance based m profile based

Mobile IP

36 Mobile IP: Architecture r Assume the current Internet addressing and routing architecture r Design extensions to handle out of network devices

37 Mobile IP: Terminology r Mobile Node (MN) m the node under consideration r Home Agent (HA) m a stationary network node (e.g., a router) at the home network r Foreign Agent (FA) m a network node (e.g. a router) in the foreign network r Care-of Address (COA) m the address in the foreign network r Correspondent Node (CN) m communication partner

38 Internet router FA HA home network foreign network (physical home network for the MN) (current physical network for the MN) routerend-system CN mobile node MN Illustration

39 Mobile IP Operations r Basic idea of Mobile IP: m a MN acquires a COA in a foreign network from a foreign agent m registers to the home agent m all messages sent to its home address is forwarded by its home agent to its COA

40 Discovering the Agents and Care- of Address r Mobile IP discovery process m (home or foreign) agent broadcasts advertisements at regular intervals announce the network list one or more available care-of addresses m mobile node takes a care-of address m mobile node can also send solicitation to start the process

41 Registering the Care-of Address r Mobile node sends an update (called) registration request) to its home agent with the care-of address information r Home agent approves/disapproves the request r Home agent adds the necessary information to its routing table r Home agent sends a registration reply back to the mobile node

42 Registration Operations in Mobile IP r MH = Mobile HostHA = Home Agent r FA = Foreign Agent

43 Internet receiver FA HA MN home network foreign network sender 1 1. Sender sends to the IP address of the receiver as usual, FA works as default router CN Data Transfer from the Mobile Node

44 Internet sender FA HA MN home network foreign network receiver Sender sends to the IP address of MN, HA intercepts packet 2. HA tunnels packet to COA, here FA, by encapsulation 3. FA forwards the packet to the MN CN Data Transfer to the Mobile Node

45 Tunneling Operations in Mobile IP Correspondent Node X

46 Discussion r Any problems of the Mobile IP approach?

47 r Triangular Routing m CN sends all packets via HA to MN m higher latency and network load r “Solution” m CN learns the current location of MN m direct tunneling to this location m HA or MN informs a CN about the location of MN r Problem of the solution m big security problems ! Triangular Routing

48 Handoff r Change of FA (COA) m packets on-the-fly during the change can be lost r “Solution” m new FA informs old FA to avoid packet loss, old FA buffers and then forwards remaining packets to new FA m this information also enables the old FA to release resources for the MN

49 Summary: Mobile IP r An out-of-network mobile node (MN) registers its current reachable address (COA) with its home agent r Home agent forwards packets to the MN r Several optimization techniques to improve efficiency and reduce packet losses during mobility

50 Preview: How to Routing? A E D CB F

Backup Slides

52 CNHAFA old FA new MN MN changes location t Data Update ACK Data Registration Update ACK Data Warning Request Update ACK Data Change of Foreign Agent

53 Micro Mobility r A very typical scenario of Mobile IP is that a MN visits a company or university m the MN may change foreign networks multiple times in the foreign network, generating much control traffic

54 Handoff Aware Wireless Access Internet Infrastructure (HAWAII) r Operation: m MN obtains co-located COA and registers with HA m Handover: MN keeps COA, new BS answers Reg. Request and updates routers m MN views BS as foreign agent BS Backbone Router Internet BS MN BS MN Crossover Router DHCP Server HA DHCP Mobile IP