Mobility Chapter 13. More Car Network Ideas. Rating. Overview. Mobile IP Internet. First steps Text book. GSM Network. No apps Mission critical

Transcription

1 More Car Nework Ideas Mobiliy Chaper 13 CAR2CAR Consorium: Audi, BMW, Daimler, Fia, GM, Honda, Renaul, VW 13/1 Raing Overview Area mauriy Firs seps Tex book Pracical imporance No apps Mission criical Mobile IP Inerne Geo Rouing GSM Nework Theoreical imporance No really Mus have Mobiliy Simulaion 13/3

2 Basics of saic rouing NAT Domain Name Sysem DNS = = ISP ISP DHCP: ges IP, DNS servers & gaeway from ISP ISP: Inerne service provider Nework Address Translaion NAT IP por :80. 13/5 13/6 Reachabiliy behind a NAT Skype Super Node Nicolas -> : ISP Nework Address Translaion NAT IP por :80 IP por :80 Olga Mobile IP DNS = = Updae rouers & keep IP? - New IP & updae DNS? Nicolas 13/7 13/8

3 Moivaion for mobile IP Requiremens on mobile IP (RFC 4721) Rouing based on IP desinaion address, nework prefix (e.g ) deermines physical subne change of physical subne implies change of IP address o have a opological correc address (sandard IP) or needs special enries in he rouing ables Changing he IP-address? adjus he hos IP address depending on he curren locaion almos impossible o find a mobile sysem, DNS updaes are oo slow TCP connecions break securiy problems Change/Add rouing able enries for mobile hoss? worldwide! does no scale wih he number of mobile hoss and frequen changes in heir locaion Compaibiliy suppor of he same layer 2 proocols as IP no changes o curren end-sysems and rouers required mobile end-sysems can communicae wih fixed sysems Transparency mobile end-sysems keep heir IP address coninuaion of communicaion afer inerrupion of link possible poin of connecion o he fixed nework can be changed Efficiency and scalabiliy only lile addiional messages o he mobile sysem required (connecion ypically via a low bandwidh radio link) world-wide suppor of a large number of mobile sysems Securiy auhenicaion of all regisraion messages 13/9 13/10 Conacing a mobile node Conacing a mobile node HA FA foreign nework HA 2 FA foreign nework 3 home nework (physical home nework of MN) MN home nework (physical home nework of MN) 1 MN CN User (end-sysem) Mobile Node (mobile end-sysem) CN User (end-sysem) 1. Sender sends o he IP of MN, HA inerceps packe (proxy ARP) 2. HA unnels packe o FA by encapsulaion 3. FA forwards packe o he MN Mobile Node (mobile end-sysem) 13/11 13/12

4 Direc answer Terminology home nework (physical home nework of MN) CN HA User (end-sysem) FA foreign nework MN Mobile Node (mobile end-sysem) Mobile Node (MN) sysem (node) ha can change he poin of connecion o he nework wihou changing is IP address Home Agen (HA) sysem in he home nework of he MN, ypically a rouer regisers he locaion of he MN, unnels IP daagrams o he COA Foreign Agen (FA) sysem in he curren foreign nework of he MN, ypically a rouer ypically he defaul rouer for he MN Care-of Address (COA) address of he curren unnel end-poin for he MN (a FA or MN) acual locaion of he MN from an IP poin of view can be chosen, e.g., via DHCP Corresponden Node (CN) 13/13 13/14 Overview home nework (physical home nework of MN) CN HA 1 User (end-sysem) 2 COA HA unnels packes o he COA of he FA FA foreign nework 3 MN Mobile Node (mobile end-sysem) How i works Agen Adverisemen HA and FA periodically send adverisemen messages ino heir physical subnes MN lisens o hese messages and deecs if i is in he home or a foreign nework (sandard case for home nework) MN reads a COA from he FA adverisemen messages Regisraion (always limied lifeime!) MN signals COA o he HA via he FA, HA acknowledges via FA o MN hese acions have o be secured by auhenicaion Adverisemen HA adverises he IP address of he MN (as for fixed sysems), i.e. sandard rouing informaion rouers adjus heir enries, hese are sable for a longer ime (HA responsible for a MN over a longer period of ime) packes o he MN are sen o he HA independen of changes in COA/FA 13/15 13/16

5 Direc answer may no work Reverse unneling (RFC 2344) HA FA foreign nework HA 2 FA foreign nework 1 home nework (physical home nework of MN) MN home nework (physical home nework of MN) 3 MN CN User (end-sysem) Problems: - Firewall a CN - TTL - Mulicas Mobile Node (mobile end-sysem) CN User (end-sysem) Mobile Node 1. MN sends o FA (mobile end-sysem) 2. FA unnels packes o HA by encapsulaion 3. HA forwards he packe o he receiver (sandard case) 13/17 13/18 Mobile IP wih reverse unneling Opimizaion of packe forwarding accep ofen only opologically correc addresses (firewall!) a packe from he MN encapsulaed by he FA is now opologically correc furhermore mulicas and TTL problems solved (TTL in he home nework correc, bu MN is oo far away from he receiver) Reverse unneling does no solve problems wih firewalls, he reverse unnel can be abused o circumven securiy mechanisms (unnel hijacking) opimizaion of daa pahs, i.e. packes will be forwarded hrough he unnel via he HA o a sender (double riangular rouing) Reverse unneling is backwards compaible he exensions can be implemened easily and cooperae wih curren implemenaions wihou hese exensions Triangular Rouing sender sends all packes via HA o MN higher laency and nework load Soluions sender learns he curren locaion of MN direc unneling o his locaion HA informs a sender abou he locaion of MN big securiy problems Change of FA packes on-he-fly during he change can be los new FA informs old FA o avoid packe loss, old FA now forwards remaining packes o new FA his informaion also enables he old FA o release resources for he MN 13/19 13/20

6 Overview Cellular Neworks Mobile IP Inerne Geo Rouing GSM Nework Mobiliy Simulaion GSM (Global Sysem for Mobile Communicaions) Sandard for a Public Land Mobile Nework (PLMN) Specificaion of he GSM sandard in 1991 More han 3 billion subscribers worldwide Over 850 GSM nework operaors GSM in Swizerland 8 million mobile phone users (2007) 5 GSM nework operaors acive: 13/22 GSM Archiecure GSM Coverage GSM is a combinaion of wireless and fixed nework sysems Base saion covers mobile users in a cell Differen base saions are conneced hrough a backbone nework Coverage in Swizerland is nearly 99.8% of he populaed area Approx base saions (anennas) placed all over he counry Cell sizes can vary from a few hundred meers up o 30 km Depends on he number of users, geography, ransceiver power Example: Zurich Ciy Source: funksender.ch, BAKOM 13/24

7 Handling Mobiliy in Cellular Neworks Addressing Scheme for Cellular Subscribers GSM designed for high mobiliy of users GSM evolved from former car elephony sandards (e.g. Nael C) Home nework: Nework of your service provider (e.g. Swisscom, Orange, ) Home Locaion Regiser (HLR) : sores profile informaion (services, billing, preferences) of all cusomers of a nework operaor Visied nework: Nework in which mobile user currenly resides Visior Locaion Regiser (VLR): conains an enry for each user currenly in he nework, enry for a mobile user is copied from he HLR of your home nework Global addressing scheme for mobile users Mobile phone numbers need o be globally unique Hierarchical addressing (counry, operaor, subscriber) Inernaional Mobile Subscriber Ideniy (IMSI) Sored on he Subscriber Ideniy Module (SIM) card 3 digis Mobile Counry Code (MCC) 2 digis Mobile Nework Code (MNC) Max. 10 digis mobile saion idenificaion number Example for an IMSI: (228 = Swizerland, 01 = Swisscom, = idenificaion number) Corresponds o he inernaional phone number /25 13/26 Mobile Terminaed Call GSM Handover Inra-nework mobiliy: User changes beween differen base saions (BSS) of he same nework operaor (handover) Seamless handover (no call drop) 1. Old BSS informs MSC of pending handover 2. MSC ses up pah (resources) o new BSS 3. New BSS signals o MSC and old BSS: ready 4. Old BSS ells subscriber o perform handover 5. MSC re-roues call o he new BSS, old BSS releases resources 1. Calling a GSM subscriber, call is forwarded o he GMSC 2. Look-up of he curren locaion in he HLR 3. Call is forwarded o he responsible MSC 4. All base saions conrolled by he MSC sar paging he subscriber 5. Mobile subscriber answers, securiy checks, call seup 13/27 Someimes i is even necessary o perform a handover beween differen MSCs

8 GSM Roaming Mobiliy: IP versus GSM Iner-nework mobiliy: Home Locaion Regiser(HLR) keeps rack of he curren locaion Mobile user can be addressed by a emporary Mobile Saion Roaming Number (MSRN) 1. Call is forwarded o home nework GMSC 2. Locaion look-up in HLR, obain emporary MSRN 3. Call is forwarded o visior MSC over PSTN 4. Lookup locaion in VLR, forward call o user Mobile IP GSM Commen Home Agen (HA) Foreign Agen (FA) Care-of Address (COA) Gaeway Mobile Swiching Cener (GMSC) and Home Locaion Regiser (HLR) Visied Mobile Swiching Cener (MSC) and Visior Locaion Regiser (VLR) Mobile Saion Roaming Number (MSRN) Poin of conac o obain he curren address (IP) or roaming number (GSM) of he mobile user Sores emporary informaion abou he mobile user Temporary address (IP) or number (GSM) for he mobile user 13/30 Overview Locaion services Mobile IP Inerne Geo Rouing GSM Nework Mobiliy Simulaion Service ha maps node names o (geographic) coordinaes Should be disribued (no require for specialized hardware) Should be efficien Lookup of he posiion (or COA) of a mobile node Mobile IP: Ask home agen Home agen is deermined hrough IP (unique ID) of MN Possibly long deours even hough sender and receiver are close OK for Inerne applicaions, where laency is (normally) low Oher applicaion: Rouing in a MANET MANET: mobile ad hoc nework No dedicaed rouing hardware Limied memory on each node: canno sore huge rouing ables Nodes are mosly baery powered and have limied energy Nodes roue messages, e.g. using georouing 13/32

9 Home based georouing in a MANET Home based locaion service how good is i? How can he sender learn he curren posiion of anoher node? Flooding he enire nework is undesirable (raffic and energy overhead) Home based approach Similar o Mobile IP, each node has a home node, where i sores and regularly updaes is curren posiion The home is deermined by he unique ID of he node. One possibiliy is o hash he ID o a posiion p and use he node closes o p as home. Thus, given he ID of a node, every node can deermine he posiion of he corresponding home. Home based rouing 1. Roue packe o h, he home of he desinaion 2. Read he curren posiion of 3. Roue o s h p Visiing he home of a node migh be waseful if he sender and receiver happen o be close, bu he home far away The rouing srech is defined as srech := lengh of roue lengh of opimal roue We wan rouing algorihms wih low srech. Simulaneous message rouing and node movemen migh cause problems Can we do beer? s h p h p s Classificaion of locaion services Locaion services: Lookup & Publish Proacive Mobile node divulges is posiion o all nodes whenever i moves E.g. hrough flooding Reacive Sender searches mobile hos only when i wans o send a message E.g. hrough flooding Hybrid Boh, proacive and reacive. Some nodes sore informaion abou where a node is locaed Arbirarily complicaed sorage srucures Suppor for simulaneous rouing and node mobiliy Any node A can invoke o basic operaions: Lookup(A, B): A asks for he posiion of B Publish(A, x, y): A announces is move from posiion x o y Open quesions How ofen does a node publish is curren posiion? Where is he posiion informaion sored? How does he lookup operaion find he desired informaion? Goal Minimize srech = lengh of roue lengh of opimal roue 13/35 13/36

10 Locaion Service: Goals Publish cos should depend only on moved disance Lookup cos should depend only on he disance beween he sender and receiver (bounded srech) Nodes migh move arbirarily a any ime, even while oher nodes issue lookup requess Deermine he maximum allowed node speed under which delivery is sill guaraneed Locaion Service: Iniial observaions Canno ge reasonable srech wih a single home. Therefore, use several homes (locaion servers). If he sender s is close o he desinaion, a locaion server should be close s 7 srech If he sender is furher away, is OK o walk a bi longer unil finding a locaion server s 26 srech locaion server which sores he locaion of 13/37 13/38 Locaion Service: Iniial observaions Many locaion servers close o he node Sparser disribuion of locaion servers he furher away we are Boundary of he nework MLS: Locaion Service for Mobile Ad Hoc Neworks Geomeric decomposiion of he nework ino quadraic cells on several levels Level-1 (2 M,2 M ) Locaion server for node Level-M 13/39 (0,0) Level-(M-1) 13/40

11 Locaion poiners (aka locaion servers) Locaion poiner & Noaion On every level, sores one locaion poiner in he cell conaining L M denoes he quadraic cell on level M conaining On level k, he locaion poiner for is called LP M Noaion: LP k Locaion poiner for node on level-k L k Level-k cell ha conains node L M LP M L 0 The locaion poiners are placed depending on he ID of he node, as in he home-based lookup sysem. LP 1 L 1 The posiion of LP k is obained by hashing he ID of node o a posiion in. The locaion poiner is sored on he neares node. L k LP M 1 L 2 L M 1 LP 2 13/42 Rouing in MLS Rouing from a node s o a node consiss of wo phases: 1. Find a locaion poiner LP k 2. Once a firs locaion poiner is found on level-k, we know in which of he 4 sub-squares is locaed and hus in which L k 1 has published is locaion poiner LP k 1. Recursively, he message is roued owards locaion poiners on lower levels unil i reaches he lowes level, from where i can be roued direcly o. Rouing in MLS (2) When a node s wans o find a locaion poiner of a node, i firs searches in is immediae neighborhood and hen exends he search area wih exponenial growing coverage. Firs, ry o find a locaion poiner LP 0 in L s 0 or one of is 8 neighboring levels. Repea his search on he nex higher level unil a LP is found k The lookup pah draws a spiral-like shape wih exponenially increasing radius unil i finds a locaion poiner of. Once a locaion poiner is found, he lookup reques knows in which sub-square i can find he nex locaion poiner of. s 13/43 13/44

12 Suppor for mobiliy in MLS Lazy publishing A locaion poiner only needs o be updaed when he node leaves he corresponding sub-square. LP 2 is OK as long as remains in he shaded area. Mos of he ime, only he closes few locaion poiners need o be updaed due o mobiliy. LP i+2 LP 1 LP 2 LP k Idea: Don updae a level poiner as long as is sill somewha close o he level L k where poins. LP i+2 LP i+1 LP k No enough: If a node moves across a level boundary, many poiners need o be updaed. E.g. a node oscillaes beween he wo poins a and b. LP i+1 LP i+1 LP i Breaks he lookup: LP i+1 poins o a level ha does no conain LP i LP i LP i ab 13/46 Lazy publishing wih forwarding poiners Concurrency in MLS No problem, add a forwarding poiner ha indicaes in which neighboring level he locaion poiner can be found. LP i+2 Allowing for concurren lookup requess and node mobiliy is somewha ricky, especially he deleion of poiners. Noe ha a lookup reques needs some ime o ravel beween locaion poiners. The same holds for requess o creae or delee locaion (or forwarding) poiners. LP i+1 FP i LP i Example: A lookup reques follows LP i+1, and node moves as indicaed updaes is LP i and LP i+1 and removes he FP i and he old LP i The lookup reques fails if i arrives afer he has been removed FP i LP i+1 FP i LP i LP i 13/47 13/48

13 Concurrency in MLS (2) Properies of MLS No problem eiher: Insead of removing a locaion poiner or forwarding poiner, replace i wih a emporary poiner ha remains here for a shor ime unil we are sure ha no lookup reques migh arrive anymore on his oudaed pah. Similar o he forwarding poiner, a emporary poiner redirecs a lookup o he neighbor level where he node is locaed. LP i+1 TP i LP i TP i Consan lookup srech The lengh of he chosen roue is only a consan longer han he opimal roue Publish cos is O(d log d) where moved disance is d Even if nodes move considerably, he induced message overhead due o publish requess is moderae. Works in a concurren seup Lookup requess and node movemen migh inerleave arbirarily Nodes migh no move faser han 1/15 of he underlying rouing speed We can deermine he maximum node speed ha MLS suppors. Only if nodes move faser, here migh arise siuaions where a lookup reques fails. 13/49 13/50 MLS Conclusions Hisory of locaion services I s somewha ricky o handle concurrency properly Use of emporary forwarding poiners MLS is he firs locaion service ha deermines he maximum speed a which nodes migh move Wihou he speed limiaion, no delivery guaranees can be made! Drawbacks MLS uilizes an underlying rouing algorihm ha can deliver messages wih consan srech given he posiion of he desinaion MLS requires a relaively dense node populaion Grid Locaion Service (GLS) by Li e al. (2000) No bound on he srech Localiy Aware Locaion Service (LLS) by Abraham e al. (2004) Similar o MLS No concurrency suppor MLS: Locaion Service for Mobile Neworks by Flury e al. (2006) Sill many open problems o solve 13/51 13/52

14 Overview Mobiliy Models Mobile IP Inerne GSM Nework Mobiliy is an imporan aspec when designing proocols for wireless ad-hoc neworks Node densiy depends highly on he mobiliy paern Links break more frequenly when he node mobiliy is high Geo Rouing Mobiliy Simulaion When sudying mobiliy, one migh resolve o models Simulaions of mobiliy models are fas, cheap and repeaable Real-world experimens are ofen infeasible Mobiliy models specify how nodes move in a cerain area of ineres Many differen ideas how o model mobiliy (e.g. physics, road raffic) Only key feaures are aken ino accoun o keep he model simple (bu ofen oo simplified) Should mach he real-world behavior of nodes as good as possible 13/54 Mobiliy Model Classificaion The Random Waypoin Model [following slides by JY Le Boudec, EPFL] Random eniy-based mobiliy models Each node acs independenly of oher nodes (e.g. Brownian moion, Random waypoin, Random rip) Group-based mobiliy models Simulae he behavior of nodes moving ogeher owards a common desinaion (e.g. Reference Poin Group Mobiliy model) Survey-based mobiliy models Sree maps, augmened wih info wha kind of people live/work/shop/ in which areas, and how do hey move beween hese areas This is also popular in research abou viruses and diseases Vehicular mobiliy models Model he behavior of vehicles paricipaing in road raffic Driver models, inersecions, congesion Traffic simulaors In is simples form: Mobile picks nex waypoin M n uniformly in area Mobile picks nex speed V n uniformly in [v min ; v max ] Boh independen of pas and presen Mobile moves owards M n a consan speed V n M n-1 M n 13/55

15 The Random Trip model Example: Random Trip Random Waypoin is a special case of Random Trip: Mobile picks a pah in a se of pahs and a speed A end of pah, mobile picks a new pah and speed Mobiles may decide o wai and sleep a desinaions before going on he nex leg E.g. shores Euclidean pah in non-convex area, or shores pah on sree map 13/57 Simulaion problems Simulaion soluions If you simulae mobiliy, you need o ake care abou sysem leveling off The problem is ha your simulaions may show resuls which differ from realiy. A simple rule of humb (which is wrong, bu somehow accepable ): If you wan o simulae for ime T, you really need o simulae ime 2T, and hrow he firs half of your simulaion away. Samples of locaion a imes 0s and 2000s The problem is ha he seady-sae is in he infinie Average node speed Anoher (also wrong) soluion is o sar each node a a posiion p which is uniformly random beween uniformly random poins s and, and wih velociy according o he disribuion 1/v. However, also his is no correc 13/59 13/60

16 Simulaion soluion Vehicular Mobiliy Models The correc soluion is o simulaneously draw posiion and velociy from he seady-sae disribuion (see work by Le Boudec for deails.) Global behavioral rules Random rips consrained o a realisic road nework (GIS) Local behavioral rules Speed adjusemen and car-following (keep minimal disance o he car in fron) Inersecion managemen (sop a red raffic lighs, hen sar o accelerae again on green ligh) Example: Vehicular Mobiliy using GIS daa Impac of he Mobiliy Model on he Nework Topology Use he road opology from a geographic informaion sysem (GIS) o model vehicular mobiliy for a simulaion area Informaion abou road caegory, speed limis Very deailed geographical daa available (resoluion is around 1m) Choosing he righ mobiliy model is imporan Should mach he realiy as close as possible Mobiliy model has a large impac on he node disribuion and herefore also on he nework opology Example: Nework opolgy for Random Waypoin (lef) and a vehicular mobiliy model(righ) Map Nework graph

17 Open problem Even sysems like MLS sill make way oo many simplifying assumpions. So here is he obvious quesion abou a locaion service which is pracical. Essenially a good locaion service sysem needs o 1. work in dynamic environmens 2. give accepable memory and communicaion loads 3. provide srech guaranees 4. neiher make funny assumpions abou node disribuions 5. nor abou mobiliy paerns 6. be secure 13/65