mạng máy tính phạm trần vũ bài giảng 13 wireless and mobile

Computer Networks (Mạng Máy Tính 1) Lectured by: Dr Phạm Trần Vũ SinhVienZone.com https://fb.com/sinhvienzonevn Chapter Wireless and Mobile Networks Computer Networking: A Top Down Approach , 5th edition Jim Kurose, Keith Ross Addison-Wesley, April 2009 All material copyright 1996-2009 J.F Kurose and K.W Ross, All Rights Reserved SinhVienZone.com Introduction https://fb.com/sinhvienzonevn 1-2 Chapter 6: Wireless and Mobile Networks Background:  # wireless (mobile) phone subscribers now exceeds # wired phone subscribers!  computer nets: laptops, palmtops, PDAs, Internet-enabled phone promise anytime untethered Internet access  two important (but different) challenges   wireless: communication over wireless link mobility: handling the mobile user who changes point of attachment to network SinhVienZone.com 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-3 Chapter outline 6.1 Introduction Wireless  6.2 Wireless links, characteristics  CDMA  6.3 IEEE 802.11 wireless LANs (“wi-fi”)  6.4 Cellular Internet Access   architecture standards (e.g., GSM) SinhVienZone.com Mobility  6.5 Principles: addressing and routing to mobile users  6.6 Mobile IP  6.7 Handling mobility in cellular networks  6.8 Mobility and higherlayer protocols 6.9 Summary 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-4 Elements of a wireless network network infrastructure SinhVienZone.com wireless hosts  laptop, PDA, IP phone  run applications  may be stationary (non-mobile) or mobile  wireless does not always mean mobility 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-5 Elements of a wireless network network infrastructure SinhVienZone.com base station  typically connected to wired network  relay - responsible for sending packets between wired network and wireless host(s) in its “area”  e.g., cell towers, 802.11 access points 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-6 Elements of a wireless network network infrastructure SinhVienZone.com wireless link  typically used to connect mobile(s) to base station  also used as backbone link  multiple access protocol coordinates link access  various data rates, transmission distance 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-7 Characteristics of selected wireless link standards Data rate (Mbps) 200 54 5-11 802.11n 802.11a,g 802.11b 802.11a,g point-to-point data 802.16 (WiMAX) UMTS/WCDMA-HSPDA, CDMA2000-1xEVDO 3G cellular enhanced 802.15 384 UMTS/WCDMA, CDMA2000 056 3G 2G IS-95, CDMA, GSM Indoor Outdoor 10-30m 50-200m SinhVienZone.com Mid-range outdoor Long-range outdoor 200m – Km 5Km – 20 Km 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-8 Elements of a wireless network network infrastructure SinhVienZone.com infrastructure mode  base station connects mobiles into wired network  handoff: mobile changes base station providing connection into wired network 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-9 Elements of a wireless network ad hoc mode  no base stations  nodes can only transmit to other nodes within link coverage  nodes organize themselves into a network: route among themselves SinhVienZone.com 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-10 Chapter outline 6.1 Introduction Wireless  6.2 Wireless links, characteristics  CDMA  6.3 IEEE 802.11 wireless LANs (“wi-fi”)  6.4 Cellular Internet Access   architecture standards (e.g., GSM) SinhVienZone.com Mobility  6.5 Principles: addressing and routing to mobile users  6.6 Mobile IP  6.7 Handling mobility in cellular networks  6.8 Mobility and higherlayer protocols 6.9 Summary 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-56 Mobile IP  RFC 3344  has many features we’ve seen:  home agents, foreign agents, foreign-agent registration, care-of-addresses, encapsulation (packet-within-a-packet)  three components to standard:  indirect routing of datagrams  agent discovery  registration with home agent SinhVienZone.com 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-57 Mobile IP: indirect routing foreign-agent-to-mobile packet packet sent by home agent to foreign agent: a packet within a packet dest: 79.129.13.2 dest: 128.119.40.186 dest: 128.119.40.186 Permanent address: 128.119.40.186 dest: 128.119.40.186 Care-of address: 79.129.13.2 packet sent by correspondent SinhVienZone.com 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-58 Mobile IP: agent discovery  agent advertisement: foreign/home agents advertise service by broadcasting ICMP messages (typefield = 9) type = 24 checksum =9 code = =9 H,F bits: home and/or foreign agent R bit: registration required 16 standard ICMP fields router address type = 16 length registration lifetime sequence # RBHFMGV bits reserved or more care-ofaddresses SinhVienZone.com mobility agent advertisement extension 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-59 Mobile IP: registration example home agent HA: 128.119.40.7 foreign agent COA: 79.129.13.2 visited network: 79.129.13/24 ICMP agent adv COA: 79.129.13.2 … registration req COA: 79.129.13.2 HA: 128.119.40.7 MA: 128.119.40.186 Lifetime: 9999 identification: 714 encapsulation format … Mobile agent MA: 128.119.40.186 registration req COA: 79.129.13.2 HA: 128.119.40.7 MA: 128.119.40.186 Lifetime: 9999 identification:714 … registration reply time SinhVienZone.com HA: 128.119.40.7 MA: 128.119.40.186 Lifetime: 4999 Identification: 714 encapsulation format … registration reply HA: 128.119.40.7 MA: 128.119.40.186 Lifetime: 4999 Identification: 714 … 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-60 Components of cellular network architecture recall: correspondent wired public telephone network MSC MSC MSC MSC MSC different cellular networks, operated by different providers SinhVienZone.com 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-61 Handling mobility in cellular networks  home network: network of cellular provider you subscribe to (e.g., Sprint PCS, Verizon)  home location register (HLR): database in home network containing permanent cell phone #, profile information (services, preferences, billing), information about current location (could be in another network)  visited network: network in which mobile currently resides  visitor location register (VLR): database with entry for each user currently in network  could be home network SinhVienZone.com 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-62 GSM: indirect routing to mobile home network HLR home MSC consults HLR, gets roaming number of mobile in visited network correspondent home Mobile Switching Center VLR Mobile Switching Center home MSC sets up 2nd leg of call to MSC in visited network mobile user visited network SinhVienZone.com Public switched telephone network call routed to home network MSC in visited network completes call through base station to mobile 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-63 GSM: handoff with common MSC  Handoff goal: route call via new base station (without interruption)  reasons for handoff: VLR Mobile Switching Center old routing old BSS  new routing  new BSS  stronger signal to/from new BSS (continuing connectivity, less battery drain) load balance: free up channel in current BSS GSM doesn’t mandate why to perform handoff (policy), only how (mechanism)  handoff initiated by old BSS SinhVienZone.com 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-64 GSM: handoff with common MSC VLR Mobile Switching Center old BSS SinhVienZone.com new BSS old BSS informs MSC of impending handoff, provides list of 1+ new BSSs MSC sets up path (allocates resources) to new BSS new BSS allocates radio channel for use by mobile new BSS signals MSC, old BSS: ready old BSS tells mobile: perform handoff to new BSS mobile, new BSS signal to activate new channel mobile signals via new BSS to MSC: handoff complete MSC reroutes call MSC-old-BSS resources released 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-65 GSM: handoff between MSCs  home network correspondent Home MSC anchor MSC: first MSC visited during cal  call remains routed through anchor MSC  new MSCs add on to end anchor MSC PSTN MSC MSC MSC (a) before handoff SinhVienZone.com of MSC chain as mobile moves to new MSC  IS-41 allows optional path minimization step to shorten multi-MSC chain 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-66 GSM: handoff between MSCs  home network correspondent Home MSC anchor MSC: first MSC visited during cal  call remains routed through anchor MSC  new MSCs add on to end anchor MSC PSTN MSC MSC MSC (b) after handoff SinhVienZone.com of MSC chain as mobile moves to new MSC  IS-41 allows optional path minimization step to shorten multi-MSC chain 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-67 Mobility: GSM versus Mobile IP GSM element Comment on GSM element Mobile IP element Home system Network to which mobile user’s permanent phone number belongs Home network Gateway Mobile Switching Center, or “home MSC” Home Location Register (HLR) Home MSC: point of contact to obtain routable address of mobile user HLR: database in home system containing permanent phone number, profile information, current location of mobile user, subscription information Home agent Visited System Network other than home system where mobile user is currently residing Visited network Visited Mobile services Switching Center Visitor Location Record (VLR) Visited MSC: responsible for setting up calls to/from mobile nodes in cells associated with MSC VLR: temporary database entry in visited system, containing subscription information for each visiting mobile user Foreign agent Mobile Station Roaming Number (MSRN), or “roaming number” Routable address for telephone call segment between home MSC and visited MSC, visible to neither the mobile nor the correspondent Care-ofaddress SinhVienZone.com 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-68 Wireless, mobility: impact on higher layer protocols  logically, impact should be minimal … best effort service model remains unchanged  TCP and UDP can (and do) run over wireless, mobile  … but performance-wise:  packet loss/delay due to bit-errors (discarded packets, delays for link-layer retransmissions), and handoff  TCP interprets loss as congestion, will decrease congestion window un-necessarily  delay impairments for real-time traffic  limited bandwidth of wireless links  SinhVienZone.com 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-69 Chapter Summary Wireless  wireless links:    capacity, distance channel impairments CDMA  IEEE 802.11 (“wi-fi”)  CSMA/CA reflects wireless channel characteristics  cellular access  architecture  standards (e.g., GSM, CDMA-2000, UMTS) SinhVienZone.com Mobility  principles: addressing, routing to mobile users    home, visited networks direct, indirect routing care-of-addresses  case studies  mobile IP  mobility in GSM  impact on higher-layer protocols 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6-70 ... Principles: addressing and routing to mobile users  6.6 Mobile IP  6.7 Handling mobility in cellular networks  6.8 Mobility and higherlayer protocols 6.9 Summary 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn... Principles: addressing and routing to mobile users  6.6 Mobile IP  6.7 Handling mobility in cellular networks  6.8 Mobility and higherlayer protocols 6.9 Summary 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn... Mbps) QAM16 (4 Mbps) BPSK (1 Mbps) 6: Wireless and Mobile Networks https://fb.com/sinhvienzonevn 6 -13 Wireless network characteristics Multiple wireless senders and receivers create additional problems