Network Layer Location Management Mobile IP Acknowledgement slides borrowed from Richard Y Yang Yale Recap Wireless Link Layer The basic services of the link layer link access interference hidden terminal quality of service and fairness control framing link reliability etc Guided by network layer transmit to which neighbor at what quality S E F B C M J A L G H K I D N 2 Network Layer Services Transport packets from source to dest Network layer protocol in every host router S1 B Basic functions Control plane A E D2 C J G S2 I K M L D1 N compute routing from sources to destinations Data plane forwarding move packets from input interface to appropriate output interface s 3 Network Layer API API provided to upper layer transmit info src dest A key decision in network layer design is how to represent destinations we refer to how applications specify destinations as the addressing scheme the supported addressing scheme s can have profound impacts on usability flexibility and scalability 4 Discussion How to Specify a Destination S E F B C M J A L G H K I D N 5 Two Basic Approaches for Identifying Destinations Locators encode locations on network topology B C A F D E Identifiers ID independent of network topology 6 Addressing Scheme Sensornet Example Destination message to a sensor e g who detected fire ID D Lat 37 3169 Long 121 8740 temperature highest S B A E D C J G F I K M L D N 7 Addressing Scheme Telephone Very first scheme connection by operators to business ID or locator The telephone numbering scheme 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 8 Telephone Addressing Scheme E 164 Maximum 15 digits Hierarchical addressing scheme country code national destination code optional subscriber number e g 1 203 432 6400 Why hierarchical addressing scheme 203 432 uniquely determines the switch upon which the telephone is attached to Issues of such a scheme S E D B C M L J A F G D K I N 9 Addressing Scheme Internet How to specify the destination which is the color printer on the 4th floor of AKW Internet domain name lw4c cs yale edu Internet protocol IP address 128 36 231 8 building AKW floor 4 entity printer quality color 10 Addressing Scheme IP IP address 32 bit identifier for an interface An IP address is associated with an interface sbin ifconfig a 223 1 1 1 223 1 2 1 223 1 1 2 223 1 1 4 223 1 1 3 223 1 2 9 223 1 3 27 223 1 2 2 223 1 3 2 223 1 3 1 223 1 3 2 11011111 00000001 00000011 00000010 223 1 3 2 11 IP Addressing Hierarchical scheme network part high order bits host part low order bits 223 1 1 2 223 1 1 1 223 1 1 4 223 1 1 3 223 1 9 2 223 1 7 0 What s a network from IP address perspective 223 1 9 1 223 1 8 1 device interfaces with same network part of IP address 223 1 2 6 link layer can reach each other 223 1 2 1 223 1 2 2 223 1 8 0 223 1 7 1 223 1 3 27 223 1 3 1 223 1 3 2 12 Why Hierarchy 223 1 1 2 223 1 1 1 The hierarchy is important for the scalability of Internet routing The routing system handles only the number of networks 275 280 networks on Jan 3 2009 625 mil hosts in Jan 2009 223 1 1 4 223 1 1 3 223 1 9 2 223 1 9 1 223 1 8 1 223 1 7 0 223 1 8 0 223 1 2 6 223 1 2 1 http ftp isc org www survey reports current 223 1 7 1 223 1 3 27 223 1 2 2 223 1 3 1 223 1 3 2 13 Routing in IP Telephone Networks Represent network as a graph Determine a path to each destination on the graph Q what does a node in the graph represent 5 2 A B 2 1 D 3 C 3 1 5 F 1 E 2 14 Key Problems B C A Location management F D E 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 Dynamic routing 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 Broadcast wireless there can be interference among links and paths need good link performance metrics or scheduling 15 Next Location management in cellular networks 16 Routing in Cellular Networks Cellular networks face the location management problem a phone may be out of its home switch B C A F D E How GSM handles out of switch phones a global home location register HLR database for each carrier each base transceiver station BTS has a visitor location register VLR 17 MS mobile station BSC base station controller BTS base transceiver station MSC mobile switching center GMSC gateway MSC GSM Network Switching Subsystem and Operation Subsystem HLR GMSC fixed network MSC MSC BSC MS BSC MS Radio Subsystem VLR BTS MS MS MS VLR BTS VLR BTS MS VLR BTS VLR BTS 18 Two Primitives for Cellular Location Management Mobile station reports to the network of the cell it is in called update uses the uplink channel Network queries different cells to locate a mobile station called paging uses the downlink channel 19 Performance of the Two Primitives A city with 3M users During busy hour 11 am noon Assume each paging message is 100 bits Update only update messages 25 84 millions Q why so many update messages Paging only paging traffic 1433 calls sec Q how many bits 20 Location Management Through Location Areas LA A hybrid of paging and update Used in the current cellular networks such as GSM Partitions the cells into location areas LA e g around 10 cells in diameter in current systems Each cell BTS periodically announces its LA id If a mobile station arrives at a new location area it updates the base station about its presence When locating a MS the network pages the cells in an LA 21 How to Decide the LAs A Simple Model Assume the cells are given Cell i has on average Ni users in it during one unit time each user receives c calls per unit time There are Nij users move from cell i to cell j in N a unit of time 12 Cell 2 Cell 1 N1 N21 N2 22 How to Decide the LAs A Simple Scenario N12 Cell 2 Cell 1 N1 N21 N2 Separate LAs for cells 1 and 2 update cost N12 N21 paging cost c N1 N2 Merge cells 1 and 2 into a single LA update cost …