Understanding Components & Challenges of Host Mobility in Mobile Networking, Lecture notes of Energy Efficiency

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Mobile Networking ITS 413 – Internet Technologies and Applications ITS 413 - Mobile Networking 2 Next Generation Wireless Networks Ubiquitous mobile access to Internet ITS 413 - Mobile Networking 5 Enabling Technologies • What technologies will enable these scenarios? – Wired Networks • Even though many scenarios required freedom from wires, wired networks are still vital (providing access where possible; interconnecting networks; …) – Wireless Networks (Physical, Data link layers) • Faster data rates, more efficient use of spectrum, energy efficiency, … – 3G+ mobile networks: 14Mb/s download to mobile phone available – IEEE 802.16 (WiMax), IEEE 802.20: 10’s Mb/s over km’s – IEEE 802.11n (300Mb/s) and beyond – Internet Mobility (Network layer) • Ability to move between networks without changing your IP address (Host Mobility) • Ability for entire networks to move within Internet without changing network address or IP address of hosts on network (Network Mobility) – Infrastructure-less or Ad Hoc Networks (Network and other layers) • No longer rely on fixed (expensive) base stations with wired connections • Wireless connections between users for dynamic networks – Mesh networks, Mobile Ad Hoc Networks, Sensor Networks ITS 413 - Mobile Networking 6 Enabling Technologies • What technologies will enable these scenarios? – Applications and Supporting Protocols (Transport, Application layers) • New applications that make it possible to use services across different networks – Video data rate automatically reduced when move from WiFi to WiMax • Take advantage of mobility – Location based services: maps, information updates, discovering services, … – Devices • Support multiple wireless technologies – Many mobile phones have tri/quad-band 2G/3G access, Bluetooth, wireless LAN … in future, WiMax and others (and your PDA, MP3 player, digital camera etc. also have access) • User interface • Energy efficiency – And many others … • Security, quality of service, network management, … • Our Focus: Mobility Issues, especially at Layer 3 (Network) ITS 413 - Mobile Networking 7 Contents • Host Mobility – IP Mobility and Mobile IP • Network Mobility – NEMO • Ad Hoc Networking – MANETs ITS 413 - Mobile Networking 10 Assumptions: Wireless Access Networks • Lets assume an “Access Network” is a single IP network where end-user hosts connect (via layer 2 technologies) to a router – Hosts and router all use same Network portion of IP address • Access Networks are connected together via other IP networks (often called Core, Backbone or Transport networks) X.a Router X.z X.b X.c X.d Access Network X Access Network X Access Network Y Access Network Z Internet 11 Problems with Mobility in Internet • The Internet uses topologically correct routing – Routers in the Internet know about the location of other Networks (not hosts) • E.g. when Z.a sends to X.b, Internet routing finds a path to Network X, then Router X.z uses direct delivery to send to X.b – Therefore, if a mobile host changes Access Networks, then must change IP address, otherwise routing will not work • E.g. when X.b moves to Network Y, it cannot use the same IP address X.b! InternetX.a Router X.z X.b Router Y.z Y.f Y.e Router Z.z Z.a Host mobility ? ITS 413 - Mobile Networking 12 Problems with Mobility in Internet • Application Sessions depend on IP address – Most Internet applications (and all using TCP) define a session as using the same: • Source IP address, Source Port, Destination IP address, Destination Port – Changing one of these identifiers, requires ending of the current session and starting a new session • E.g. stop a file transfer, lose context for web browsing, reconnect for a voice call, interrupt a database transaction – These interruptions are acceptable for nomadicity • Turning your laptop off, move to another location, and restart laptop • DHCP (and similar techniques) can be used to give your mobile host a new IP address – BUT these interruptions are not acceptable for true mobility • A user changing access networks should not be aware of the change • Mobility should be seamless (perhaps small delays of 10’s to 100’s of milliseconds incurred) • Very important for multimedia, streaming applications, e.g. voice over IP • Solution: change the IP address, but hide the change from Transport/Application layers – Solution is implemented by Mobile IP, an IETF standard ITS 413 - Mobile Networking 15 Mobile IP Components • Nodes (or Hosts): – Mobile Node (MN): a node that uses Mobile IP – Correspondent Node (CN): a node that communicates with a MN (may or may not use Mobile IP) • Home: – Every node has a single Home Network; the network in which the host is assigned its normal IP address – From a nodes point of view, all networks other than the Home Network are Foreign Networks • Home Agent (HA) – A server on the Home Network that keeps track of where the Mobile Nodes associated with that Home Network are – Maintains a Mobility Binding Table: for its own MNs, records their current COA – Implemented on a router in the Home Network • Foreign Agent (FA) – A server that keeps track of Mobile Nodes visiting its network, providing the necessary addresses and forwarding for those visiting Mobile Nodes – Maintains a Visitors List: for the visiting MNs, records their Home IP, Home Agent and Layer 2 address – Implemented on a router in a Foreign Network ITS 413 - Mobile Networking 16 Mobile IP Components • Home IP Address – The IP address assigned to the MN in its Home Network – The Home IP address is within the Home Network address range • E.g. home network: 25.105.0.0/16; home address: 25.105.23.88/16 • Care-of-Address (COA) – An IP address assigned to MN visiting a Foreign Network – The COA is an IP address within the Foreign Network address range • E.g. foreign network: 172.16.37.0/24; COA: 172.16.37.65/24 – The IP address of FA may be assigned as the COA of visiting MN • E.g. FA 172.16.37.1/24; COA: 172.16.37.1/24 ITS 413 - Mobile Networking 17 Mobile IP Forwarding • Correspondent Node to Mobile Node – CN is not aware that MN is “mobile” – Sends packets to Home IP, e.g. X.b – HA intercepts and realises the MN is not home, and forwards to Foreign Network where MN is visiting • Mobile Node to Correspondent Node – MN sends packets to CN (e.g. Z.a) via the local FA – Source Address is MN’s Home IP (e.g. X.b) X.a Router X.z HA Router: Y.z FA Y.fY.e Router Z.z FA Z.a CN HomeIP: X.b COA: Y.m Home Network (for X.b) Foreign Network (for X.b) Foreign Network (for X.b) ITS 413 - Mobile Networking 20 Mobile IP Agent Discovery • How does a MN know the IP address of the FA? – When it first powers up? – When it performs a handover from an old FA to a new FA? • Three options for Agent Discovery: – IP Level Agent Advertisements • Agent broadcasts periodic advertisements, indicating its own IP address • ICMP Router Advertisement messages, extended to carry Mobile IP information • Rate at which advertisements are sent must be limited (default: 1 per sec) • Agent may be configured to only send advertisement after receiving solicitation – IP Level Router Solicitation • MN broadcasts a solicitation message to the network • ICMP Router Solicitation messages are used • Rate MUST be limited (1 per second for the 3 initial solicitation messages, and then with exponential back-off) • The FA has to respond to solicitation with an advertisement message – Layer 2 Supported Techniques • Local broadcasts of L2 beacon frames with all necessary information (including FA address, supported functionality, CoA etc…) • MN can solicit beacon (or other L2 “welcome”) frames upon gaining L2 connectivity • Example: Wireless LAN beacons are extended to carry Mobile IP information, such as FA address 21 Mobile IP Tunnelling • CN sends IP datagrams to the Home IP address • When HA receives datagram, it checks Mobility Binding Table: if destination node is mobile, then encapsulate original datagram in another IP datagram – Source: HA; Destination: COA • FA will receive datagram, check its Visitors Table, decapsulate the datagram, and send original datagram to MN Router X.z HA Router: Y.z FA Router Z.z FA Z.a CN HomeIP: X.b COA: Y.m Tunnel Src: Z.a Dst: X.b Data Src: Z.a Dst: X.b Data Src: Z.a Dst: X.b DataSrc: X.z Dst: Y.m IP datagram sent by CN (Z.a) IP datagram received by MN (X.b) IP datagram tunnelled by HA (X.z) ITS 413 - Mobile Networking 22 Mobile IP Route Optimisation • Routing via the HA all the time can be inefficient – Triangular Routing Problem – If CN and MN are “near each other”, but HA is “far away” • E.g. CN is in Toshiba Bangkadi; MN from Toshiba US is visiting SIIT – CN (in Bangkadi) sends to HA in US, which then sends to FA/MN in Bangkadi • Route Optimisation is an extension of original Mobile IP that allows CN to send directly to MN’s COA – MN’s and FA’s may sending Binding Warnings to HA if they see a need for route optimisation – HA sends Binding Updates to CN, informing the CN of the MN’s current COA (a lifetime is associated with this COA) – CN maintains a Binding Cache, storing the COA of MN’s • If COA exists in Binding Cache, CN sends with destination set to COA • If COA does not exist, CN sends with destination set to Home IP • Reduces delay of triangular routing, but: – Requires CN to maintain Binding Cache (not supported in some nodes) – Need to have security association between HA and CN – Some security techniques that filter packets that “come from the wrong network” may not allow the packets (ingress filtering) ITS 413 - Mobile Networking 25 Mobile IP Handover Methods • Lazy Cell Switching (LCS), or “break-before-make” – Connection with old FA is maintained for as long as possible, until it is no longer available (break, 3a); then connection with a new FA is established (make, 3b) Old Foreign Agent New Foreign Agent X 1 2 3 3a 3b 4 ITS 413 - Mobile Networking 26 Mobile IP Handover Methods • Eager Cell Switching (ECS), or “make-before-break” – Contact with new FA is established as soon as Layer 2 connectivity is available (2a) – Connection with old FA may be dropped immediately or when Layer 2 connectivity is lost (3a) – Requires Layer 2 wireless technology to support simultaneous active links Old Foreign Agent New Foreign Agent 1 2 3 2a 3a 4 ITS 413 - Mobile Networking 27 Mobile IP Handover Smoothing • Delay incurred by handovers can be significant: 100msec to seconds – Hence, the user will notice the mobility; impact on performance of applications • Data may be dropped or delayed • Various optimisations have been proposed to reduced handover delay – Handover Smoothing using: • Buffering • Bicasting • Regional Registrations – Fast Handover Mobile IP • Buffering – Just before the handoff, data destined to MN is buffered at the old FA – When the handoff is finished, buffered data is forwarded from the old FA to the new FA – Buffering trade-off: data loss vs. data delay (may not be suitable for Real-Time applications) – Problems include: when to start and stop buffering; synchronisation of actions among the involved entities (MN, oFA, nFA, HA); signalling overhead; data duplication and/or loss • Bicasting – Start bicasting to both old and new FAs when handoff starts – Problems: as for buffering, with more data duplication and synchronisation challenges • Regional Registrations – Hierarchy of FAs, so only re-register with lower level FAs, not necessarily HA – Improves handover delay but increases signalling load Network Mobility NEMO ITS 413 - Mobile Networking 31 Host Mobility versus Network Mobility • Host mobility allows a single host/node to move from one access network to another – At layer 2, implemented by Wireless LAN, Bluetooth, etc. – At layer 3, implemented by Mobile IP Access Network Access Network Mobile Node Host Mobility Mobile Node ITS 413 - Mobile Networking 32 Host Mobility versus Network Mobility • Network mobility allows an entire access network to move – Implemented at Layer 3 using extensions of Mobile IP called Network Mobility (NEMO) by IETF 35 NEMO Basics • The basic features of NEMO are an extension of Mobile IPv6 • A Mobile Router is assigned a COA when it moves to a foreign network • The Mobile Router informs its HA if the new COA Network X Access Router (HA) X.h Network Y AR Y.p Mobile Network XA Mobile Router XA.e/X.e Local Mobile Node XA.g Local Fixed Node XA.f Mobile Network YB MR LMN YB.j Network Z AR Z.f Correspondent Node Z.c Visiting Mobile Node Z.t COA: YB.mMobile Network XA Mobile Router XA.e/X.e COA:Y.s LMN XA.g LFN XA.f ITS 413 - Mobile Networking 36 NEMO Components • Mobile Routers (MR) – Routers that can move, thereby resulting in the move of an entire network (the router plus the MNNs) • Mobile Network Nodes (MNN) – Nodes attached to MR via one or more layer 2 technologies – Three types of MNN: • Local Fixed Node (LFN): a normal node with a fixed connection to the MR; it does not use Mobile IP for its own mobility (e.g. always connected to the same MR) • Local Mobile Node (LMN): a Mobile IP-enabled node, with its Home Network being that of the current MR; it can change networks using standard Mobile IP • Visiting Mobile Node (VMN): a Mobile IP-enabled node, visiting the current MR; its Home Network is somewhere else • Access Router (AR) – The Router the MR connects to – This is similar to FA in Mobile IP (but in IPv6 and Mobile IPv6) the role of a FA is performed by a normal IPv6 router, hence the name change! • Note: there are other differences, especially in terminology, between IPv4 and IPv6, and hence between Mobile IPv4 and Mobile IPv6. NEMO was first defined for IPv6. However, the main concepts of supporting mobility remain the same. In this lecture we will just explain concepts. ITS 413 - Mobile Networking 37 NEMO Forwarding • Correspondent Node to Mobile Network Node Network X Access Router (HA) X.h AR Y.p MR AR Z.f Correspondent Node Z.c Mobile Router XA.e/X.e COA:Y.s LMN XA.g LFN XA.f Src: Z.c Dst: XA.g Data IP datagram sent by CN (Z.c) Src: Z.c Dst: XA.g DataSrc: X.h Dst: Y.s IP datagram tunnelled by HA (X.h) Src: Z.c Dst: XA.g Data IP datagram sent by MR (X.e) ITS 413 - Mobile Networking 40 Status of NEMO • Standardisation – NEMO Basic Support is mature: RFC3963 – Still working (and researching) on optimisations such as route optimisation, nested NEMO and multi-homing • Implementation – Several commercial routers implement MR/HA features of NEMO (e.g. Cisco) – MR and MNN features are implemented as extensions to BSD variants of Unix (e.g. FreeBSD, OpenBSD) • Use – Only used in experimental/research purposes • E.g. several “Internet Car” projects have used NEMO – May become more widespread as Internet access becomes ubiquitous in public and private vehicles Ad Hoc Networking MANETs 42 Infrastructure-Based Wireless Networks • Almost all wireless networks today are infrastructure-based or centralised: – A fixed base station (access point) provides wireless connectivity to mobile clients within some area (e.g. cell) – Base stations are connected via wires to other networks (e.g. Internet) – Examples: wireless LANs, mobile phones, satellite, WiMax, … – Single-hop wireless: mobile client to base station (the rest is wired) • Infrastructure-based wireless networks work well because the are designed for performance/coverage; can control the resources • But some problems: – Difficult to deploy: large amount of time and money to deploy – Restricted coverage: mobile clients can only have access if within a cell – Centralised: failure of a base station, means failure for all mobile clients ITS 413 - Mobile Networking 45 Applications of MANETs • Two types of networks that are similar to MANETs have many commercial applications • Mesh Networks – Some fixed wireless nodes, e.g. to form a backhaul network – Network is not as dynamic as “pure” MANET – Examples: • Mobile broadband access for emergency services • Low cost network deployment in rural/remote areas • Community-based wireless networks • Sensor Networks – Dynamic deployment, but nodes fixed – Severe resource constraints on nodes, e.g. KB of memory, MHz CPU, battery power for months – Examples: • Environmental monitoring • Precision agriculture • Surveillance and security ITS 413 - Mobile Networking 46 Technical Challenges of MANETs • The dynamic nature of MANETs lead to their main benefits, but also create many technical problems • The main problems are routing and performance – Routing • In the Internet, routing protocols (e.g. OSPF, BGP, RIP) are used to ensure routers have “up-to-date” information about routes/paths. If the network topology changes (e.g. a new router added, a link goes down), routing protocols will detect this and update the routers accordingly – Topology changes occur on a minute/daily/monthly basis • In MANETs, routing protocols are also needed, since in effect, every mobile device is a router. But topology changes (e.g. a mobile node moves) may occur every second. – Normal Internet routing protocols cannot handle such frequent changes – New MANET routing protocols have been developed, but still a difficult task – Performance • In MANETs, every node uses wireless transmission, and potentially can interfere with many other nodes. Also, only half-duplex communication is possible. • Performance of MANETs is significantly less than most other networks, e.g. throughput about 1/3 to 1/10 of a wireless LAN • Many other problems: security, connecting to Internet, applications, wireless transmission, costs, energy efficiency, … ITS 413 - Mobile Networking 47 Status of MANETs • Standardisation and Research – IETF MANET Working Group has standardised several routing protocols – Still working on methods for configuring MANETs, and connecting to Internet – Many open research problems remain unanswered • Implementation – Most implementations of MANET routing protocols are experimental • Not in common operating systems by default, but can install different MANET routing protocols • Use – Used in some commercial Mesh Networks, Sensor Networks, and by Military – Not in widespread consumer use