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Wireless Communication Protocols and Technologies by Tatiana Madsen & Hans Peter Schwefel • Mm1 Introduction. Wireless LANs (TKM) • Mm2 Wireless Personal Area Networks and Bluetooth (TKM) • Mm3 IP Mobility Support (HPS) • Mm4 Ad hoc Networks (TKM) • Mm5 Overview of GSM, GPRS, UMTS (HPS) www.kom.auc.dk/~tatiana/ WCPT: MM3, IP-Mobility Support, Spring 04 www.kom.auc.dk/~hps/ Page 1 Tatiana K. Madsen Hans Peter Schwefel Background I: Internet Protocol (IP) Internet Protocol IP, IPv4: • • Layer 3 Protocol (Network Layer) Packet (IP datagram) transmission between hosts (packet size up to 65535 bytes, often restricted by Layer 2 protocols) • • Application L5-7 TCP/UDP L4 IP L3 Link-Layer L2 Routing using 32 bit adresses (v4) Most frequent transport protocols Transmission Control Protocol TCP User Datagram Protocol UDP • Popular application layer protocols: HyperText Transfer Protocol HTTP File Transmission Protocol FTP Simple Mail Transfer Protocol SMTP WCPT: MM3, IP-Mobility Support, Spring 04 Page 2 Tatiana K. Madsen Hans Peter Schwefel Content 1. Background • 5. IP, IETF, Mobility & Handover Types 2. Mobile IP (v4) • Motivation, Principles, Messages, DHCP 3. MIP Performance aspects & improvements • HMIP, CIP 6. Mobility Support on higher layers • Transport layer mobility • Session Initiation Protocol and Mobility Summary & Outlook + Exercises 4. MIP Extensions/related topics • Security Aspects • Multi-homing/flow mobility • IPv6 and MIPv6 Goal: Make students familiar with • underlying problems • solution approaches • Overview on key technologies required to support mobility in IP-based networks WCPT: MM3, IP-Mobility Support, Spring 04 Page 3 Tatiana K. Madsen Hans Peter Schwefel Background II : IETF Standardization Internet Engineering Task Force, IETF (see http://www.ietf.org) • No formal membership; very informal process • Protocols are developed in Working Groups e.g. IPNG, mobileip, mpls, tewg, diffserv, rohc, seamoby, sip • Each WG belongs to one of 8 Areas: Applications, General, Internet, Operations and Management, Routing, Security, Sub-IP, Transport, User Services • • Area Directors form Internet Engineering Steering Group IESG Implementations (running code) required for standards Sufficient Interest BOF WG Internet Draft proposed Standard Draft Standard min. 6 months max. 24 months min. 4 months max. 24 months OK from IESG Draft changes in mailing list discussions or meetings WCPT: MM3, IP-Mobility Support, Spring 04 Tested at least 2 times At least 2 implementation s OK from IESG Page 4 Standard OK from IESG Tatiana K. Madsen Hans Peter Schwefel Background III: Mobility types Switch WLAN AP Router Router Mobile Host WLAN AP Router D WLAN AP Internet Router Router GPRS WLAN AP Cellular access (GPRS) Network Assumption in this lecture: Infrastructure networks (only first hop wireless) Different Levels of Mobility: ’Alternative’ classification: • Pico (e.g. within same radio cell) • Micro (e.g. within same subnet) • Macro (e.g. across subnets but within same administrative domain) • Global (e.g. across different administrative domains) WCPT: MM3, IP-Mobility Support, Spring 04 Page 5 • vertical mobility: changing access technology Tatiana K. Madsen Hans Peter Schwefel Background IV: Handover & more mobility types Hand-over classification: • Mobile initiated or network-initiated • Backward or forward • mobile controlled or network controlled • Mobile-assisted or network assisted or unassisted • Proactive or reactive • Make-before-break or break-before make • Soft or hard • fast (without ‚noticable‘ delay) • seamless = fast + smooth • smooth (no loss of data) More mobility types ... • Host Mobility • User Mobility • Application Mobility • Network Mobility WCPT: MM3, IP-Mobility Support, Spring 04 ... and related identifiers • IP address, hostname (DNS) • User-name (e.g. SIP URL) • --• address prefix / subnetmask Page 6 Tatiana K. Madsen Hans Peter Schwefel Mobile IP Motivation: Host mobility & Routing Problem: IP address identifies host as well as topological location Reason: IP Routing: – Routes selected based on IP destination address – network prefix (e.g. 129.13.42) determines physical subnet – change of physical subnet change of IP address to have a topological correct address Subnet A Mobile Node Subnet B IP network • Solution? Host-based routing: Specific routes to each host – Handover change of all routing table entries in each (!) router – Scalability & performance problem • Solution? Obtain new IP-address at hand-over – Problem: how to identify host after handover? DNS update performance/scalability problem – Higher protocol layers (TCP/UDP/application) need to ‘handle’ changing IP address Development of mobile IP WCPT: MM3, IP-Mobility Support, Spring 04 Page 7 Tatiana K. Madsen Hans Peter Schwefel Mobile IP: Requirements (RFC 3344) • • • • Transparency – mobile end-systems keep their IP address – point of attachment to the fixed network can be changed – continuation of communication after handover possible (transparent to transport layer in mobile node as well as to correspondent node) Compatibility – support of the same layer 2 protocols as IP – no changes to correspondent nodes and routers required Security – authentication of all registration messages Efficiency and scalability – only small data volume for additional messages to/from the mobile node (connection typically via a low bandwidth radio link) – world-wide support of a large number of mobile nodes (via the whole Internet) WCPT: MM3, IP-Mobility Support, Spring 04 Page 8 Tatiana K. Madsen Hans Peter Schwefel Mobile IP: Principles & Terminology Home network HA Mobile Node Home Address IP1 IP network FA Correspondent Node Home Address IP1 Care of Address: CoA1 Visited network Underlying Approach: separate host identifier and location identifier maintain multiple IP addresses for mobile host Terminology: • • • • • • Mobile Node (MN) with fixed IP address IP1 (home address) Home Network: subnet that contains IP1 Home Agent (HA): node in home network, responsible for packet forwarding to MN Visited Network: new subnet after roaming / handover Care-of Address (CoA): temporary IP address within visited network Foreign Agent (FA): node in visited network, responsible for packet forwarding to CoA WCPT: MM3, IP-Mobility Support, Spring 04 Page 9 Tatiana K. Madsen Hans Peter Schwefel Mobile IP: Tunneling &Triangle Routing FA Visited Network Home Network CoA1 Mobile Node IP1, CoA1 IP2 Home Agent Subnet IP1 Source: Mobile IPv4 illustrated CN sends packets to the MN using its Home Address IP1 Correspondent Node (CN) IP2 HA tunnels them to FA, using CoA1; FA forwards them to MN MN sends packets back to the CN using IP2 (without any tunneling) Home Agent needs to contain mapping of care-of address to home address (location register) WCPT: MM3, IP-Mobility Support, Spring 04 Page 10 Tatiana K. Madsen Hans Peter Schwefel Mobile IP: Tunneling Default encapsulation: • IP-within-IP (RFC2003) IP-within-IP encapsulation Other Approaches: • Minimal encapsulation (RFC2004) • Generic Routing Encapsulation (GRE) (RFC1702) WCPT: MM3, IP-Mobility Support, Spring 04 Page 11 Tatiana K. Madsen Hans Peter Schwefel Tunneling: IP in IP Encapsulation • IP-in-IP-encapsulation (support in MIP mandatory, RFC 2003) – tunnel between HA and COA ver. IHL DS (TOS) length IP identification flags fragment offset TTL IP-in-IP IP checksum IP address of HA Care-of address COA ver. IHL DS (TOS) length IP identification flags fragment offset TTL lay. 4 prot. IP checksum IP address of CN IP address of MN TCP/UDP/ ... payload • Drawback of tunneling – Possibly long routes between CN and MN (many hops) – Increase of data volume increase (additional 20 bytes IP header) possibly fragmentation WCPT: MM3, IP-Mobility Support, Spring 04 Page 12 Tatiana K. Madsen Hans Peter Schwefel Tunneling: Minimal Encapsulation • Minimal encapsulation (optional) – avoids repetition of identical fields (e.g.TTL, IHL, version, DS/TOS) – only applicable for un-fragmented packets (no space left for fragment identification) ver. IHL DS (TOS) length IP identification flags fragment offset TTL min. encap. IP checksum IP address of HA care-of address COA lay. 4 protoc. S reserved IP checksum IP address of MN original sender IP address (if S=1) TCP/UDP/ ... payload WCPT: MM3, IP-Mobility Support, Spring 04 Page 13 Tatiana K. Madsen Hans Peter Schwefel Mobile IP: Agent Discovery & Registration [Agent Solicitation] (opt.) HA FA Agent Advertisement MN Obtain c/o address Registration Request Registration Reply • Time Mobile Node finds out about FA through Agent Advertisements – FAs broadcast Advertisements in periodic intervals – Advertisements can be triggered by an Agent Solicitation from the MN • Care of Address of the MN is determined, either – Dynamically, e.g. using Dynamic Host Configuration Protocol (DHCP) – Or: use IP address of FA as CoA • MN registers at FA and HA: Registration Request & Reply – MN signals COA to the HA via the FA – HA acknowledges via FA to MN • Registration with old FA simply expires (limited life-time, soft-state) WCPT: MM3, IP-Mobility Support, Spring 04 Page 14 Tatiana K. Madsen Hans Peter Schwefel MIP messages:Agent advertisement Procedure: 0 • HA and FA periodically broadcast advertisement messages into their subnets type #addresses 7 8 • MN listens to these messages and detects, if it is in the home or a (new?) foreign network 15 16 code addr. size router address 1 preference level 1 router address 2 preference level 2 23 24 checksum lifetime 31 ... • when new foreign network: MN reads a COA from the advertisement (opt.) type = 16 length sequence number ICMP Router Discovery extension: R B H F M G r T reserved registration lifetime type = 16 COA 1 R: registration required COA 2 B: busy, no more registrations H: home agent ... F: foreign agent M: minimal encapsulation G: GRE encapsulation r: =0, ignored (former Van Jacobson compression) T: FA supports reverse tunneling reserved: =0, ignored WCPT: MM3, IP-Mobility Support, Spring 04 Page 15 Tatiana K. Madsen Hans Peter Schwefel MIP messages: registration request & reply Registration Request (via UDP) S: simultaneous bindings B: broadcast datagrams D: decapsulation by MN M mininal encapsulation G: GRE encapsulation r: =0, ignored T: reverse tunneling requested x: =0, ignored 0 7 8 type = 1 15 16 S B DMG r T x home address home agent COA 23 24 lifetime 31 identification extensions . . . Registration Reply (UDP) Example codes: registration successful • 0 registration accepted •68 home agent failed authentication •69 requested Lifetime too long 0 7 8 type = 3 • 1 registration accepted, but registration denied by HA simultaneous mobility bindings •129 administratively prohibited •131 mobile node failed unsupported registration denied by FA authentication •65 administratively prohibited •133 registration Identification mismatch •66 insufficient resources •135 too many simultaneous •67 mobile node failed mobility bindings authentication WCPT: MM3, IP-Mobility Support, Spring 04 15 16 code home address home agent 31 lifetime identification extensions . . . Page 16 Tatiana K. Madsen Hans Peter Schwefel MIP: Care-of addresses MN obtains local care-of address either • from FA Advertisement (see before) • Or via Dynamic Host Configuration Protocol (DHCP) – supplies systems with all necessary information, such as IP address, DNS server address, domain name, subnet mask, default router etc. – Client/Server-Model: client sends request via L2 broadcast server (not selected) server (selected) client initialization DHCPDISCOVER DHCPDISCOVER determine the configuration determine the configuration DHCPOFFER collection of repliesDHCPOFFER selection of configuration DHCPREQUEST DHCPREQUEST (reject) (options) DHCPACK confirmation of configuration initialization completed WCPT: MM3, IP-Mobility Support, Spring 04 Page 17 Tatiana K. Madsen Hans Peter Schwefel Content 1. Background • IP, IETF, Mobility & Handover Types 2. Mobile IP (v4) • Motivation, Principles, Messages, DHCP 5. 3. MIP Performance aspects & improvements • HMIP, CIP 4. MIP Extensions/related topics • Security Aspects • Multi-homing/flow mobility • IPv6 and MIPv6 WCPT: MM3, IP-Mobility Support, Spring 04 6. Mobility Support on higher layers • Transport layer mobility • Session Initiation Protocol and Mobility Summary & Outlook + Exercises Page 18 Tatiana K. Madsen Hans Peter Schwefel MIP Performance Aspects: Handover Events during handover • Loss of connectivity to AP (L2) • Scan for new APs • Obtain connectivity to new AP (L2) • [send Agent solicitation (L2 trigger)] • receive Agent advertisement/obtain new IP address • send registration • receive registration reply MN can receive ‚new‘ data packets from CN, when registration request is successfully processed by HA Handover delay, possible loss of data-packets (sent to old ‚FA‘ during handover) WCPT: MM3, IP-Mobility Support, Spring 04 Qu.: When can MN send packets again? Page 19 Tatiana K. Madsen Hans Peter Schwefel Intermission: Handover classification (Exercise) MIP handover is ... • Mobile initiated or network-initiated? • backward or forward? • mobile controlled or network controlled? • Mobile-assisted or network assisted or unassisted? • Proactive or reactive? • Make-before-break or break-before make? • Soft or hard? • fast (without ‚noticable‘ delay)? • smooth (no loss of data)? WCPT: MM3, IP-Mobility Support, Spring 04 Page 20 Tatiana K. Madsen Hans Peter Schwefel MIP: Performance Enhancements Techniques to achieve fast and/or smooth handover: • Layer 2 triggers (agent solicitations) • Handover prediction & multicast (simultaneous bindings) data HA Bicasting/ multicasting FA Predicted Handover MH FA2 • Bidirectional edge tunnels & buffering • Route Optimization (avoid triangular routing) • Regional Registrations WCPT: MM3, IP-Mobility Support, Spring 04 Page 21 Tatiana K. Madsen Hans Peter Schwefel Hierarchical Approaches • Optimization for: • long registration delay • inefficient routing paths • Frequent re-registration at HA (even though mostly ‘local’ mobility • Example (Hierarchical Mobile IPv4): – Hierarchy of Foreign Agents – Every FA re-tunnels the packets to the next FA until it reaches the MN – When a handoff occurs, the MN sends a regional registration request to the lowest level FA – FAs can also re-direct up-stream packets, if the destination (home-address) is registered within their domain WCPT: MM3, IP-Mobility Support, Spring 04 Page 22 Similar Approach using ‘local Home Agents’ (called Mobility Anchor Points) in HMIPv6 draft-ietf-mobileip-hmipv6-08.txt (June2003) Tatiana K. Madsen Hans Peter Schwefel Hybrid Approaches: Cellular IP • Solutions to the local management of micromobility events Internet • Mobile IP is used for global mobility Mobile IP • A gateway (GW) acts as foreign agent for each domain (all MNs use GW address as c/o) • Within the domain: host-based routing • routing cache entries using soft-state • routing cache updated by upstream packets CIP Gateway data/control packets from MN 1 • separate paging cache for in-active nodes routers within domain have to be CIP aware • Similar approach: Hand-off Aware Wireless Access Internet Infrastructure (HAWAII) WCPT: MM3, IP-Mobility Support, Spring 04 Page 23 BS MN1 BS BS packets from MN2 to MN 1 MN2 Tatiana K. Madsen Hans Peter Schwefel Content 1. Background • IP, IETF, Mobility & Handover Types 2. Mobile IP (v4) • Motivation, Principles, Messages, DHCP 5. 3. MIP Performance aspects & improvements • HMIP, CIP 4. MIP Extensions/related topics • Security Aspects • Multi-homing/flow mobility • IPv6 and MIPv6 WCPT: MM3, IP-Mobility Support, Spring 04 6. Mobility Support on higher layers • Transport layer mobility • Session Initiation Protocol and Mobility Summary & Outlook + Exercises Page 24 Tatiana K. Madsen Hans Peter Schwefel MIP Security Aspects I: Basics • (optional) General security requirements (Security Architecture for the Internet Protocol, RFC 1825) • – Authentication the origin of the data can be determined – Integrity messages cannot be modified by a third party – Confidentiality only authorized partners (e.g. sender & receiver) can read the data – Non-Repudiation sender cannot deny sending of data – Prevention of Traffic Analysis creation of traffic and user profiles should not be possible – Replay Protection replay of earlier messages by an attacker can be detected Additionally: Availability (Prevent Denial of Service Attacks) WCPT: MM3, IP-Mobility Support, Spring 04 Page 25 Tatiana K. Madsen Hans Peter Schwefel MIP security aspects II: Security associations (optional) • Security Association (SA) for registrations – extended authentication of registration MH-FA authentication FA-HA authentication MH-HA authentication registration request MH registration reply registration request FA registration reply HA – SA contains the following parameters – Destination IP address – Cryptographic method for encryption/authentication – Encryption/authentication key – Lifetime of key – Specific parameters depending on cryptographic method WCPT: MM3, IP-Mobility Support, Spring 04 Page 26 Tatiana K. Madsen Hans Peter Schwefel MIP security aspects III: Registration (optional) Registration Request Registration Reply Identification field: protection against replay attacks • time stamps: 32 bit time-stamp + 32 bit random number • Nonces: 32bit random number (MH) + 32 bit random number (HA) Identification Reg. Request Identification Reg. Reply 1010110111011011 1010110111011011 64 Identification Reg. Reply Identification next Reg. Request 1111111111111 WCPT: MM3, IP-Mobility Support, Spring 04 Page 27 1111111111111 Tatiana K. Madsen Hans Peter Schwefel MIP security aspects IV: Authentication extension • Part of Registration Messages: MN <->HA, MN<->Fa, FA<->HA (optional) •Computation of Autenticator: cryptographic keyed Hash function (e.g. HMAC-MD5 Algorithm) covering •UDP payload •All earlier extensions •Type, length and SPI of authentication extension Using the shared, secret key • SPI (security parameter index) - determines algorithm, mode, and key WCPT: MM3, IP-Mobility Support, Spring 04 Page 28 Tatiana K. Madsen Hans Peter Schwefel MIP security aspects V: Firewall traversal Ingress Filtering Problem: MN sends packets to MH CN with source address = Home Address (and not c/o address) Firewalls at domain boundaries suspect IP –Spoofing discard packets Solution: Reverse Tunneling WCPT: MM3, IP-Mobility Support, Spring 04 Firewall CH Page 29 HA Tatiana K. Madsen Hans Peter Schwefel Multi-homing and flow mobility • Multi-homing: Host supports multiple interfaces with potentially different IP addresses WLAN AP – E.g. for redundancy purposes (e.g. SCTP) – Simultaneous, multiple wireless access techniques • IP2 (WLAN) IP1 (GPRS) GPRS Network Goal: redirect different data-streams via ‚appropriate‘ interfaces – only one home address (as host identificator) – multiple c/o addresses (one per interface) Flow Mobility e.g. extension of mobile IP (IETF draft): • HA contains mapping [home address, flow identifier] c/o address • Flows identified by (ranges of) • • • Source IP addresses (CNs) Protocol type (TCP, UDP, etc.) Port Numbers WCPT: MM3, IP-Mobility Support, Spring 04 • DiffServ CodePoints • ... Page 30 Tatiana K. Madsen Hans Peter Schwefel IP Version 6 (IPv6) IPv4 • Basic Header 20 Bytes • 32-bit Network Addresses • Type of Service field • Router may fragment packets • IPsec as an enhancement • ARP (Address Resolution Protocol) • Options IPv6 • Basic Header 40 Bytes • 128-bit Network Addresses • Flow label (QoS) • No fragmentation in the network • ‘Built-in’ Security • Neighbor Discovery • Extension Headers: Routing, Fragmentation, Authentication, Encryption Offset 0 4 8 12 16 20 24 28 32 36 40 0 Version Priority 1 Payload Length 2 3 Type of Next Hdr. Hop Limit Flow Label Source Address Destination Address Next Header WCPT: MM3, IP-Mobility Support, Spring 04 Page 31 Tatiana K. Madsen Hans Peter Schwefel IPv6 in mobile settings • Large number of IP addresses (each device needs at least two addresses!) • Stateless autoconfiguration (can replace DHCP) • Extension headers (selection) – – – – – – 43 Routing Header 44 Fragment Header 51 Authentication Header 50 Encrypted Security Payload 60 Destination Options Header 0 Hop-by-hop header • Advantages for MIPv6 – Route Optimisation (via binding updates) no triangular routing – No foreign agent needed – Security easier to implement – Reverse tunneling can be avoided (c/o address as source address, home address in destination header) WCPT: MM3, IP-Mobility Support, Spring 04 Page 32 Tatiana K. Madsen Hans Peter Schwefel Content 1. Background • IP, IETF, Mobility & Handover Types 2. Mobile IP (v4) • Motivation, Principles, Messages, DHCP 5. 3. MIP Performance aspects & improvements • HMIP, CIP 4. MIP Extensions/related topics • Security Aspects • Multi-homing/flow mobility • IPv6 and MIPv6 WCPT: MM3, IP-Mobility Support, Spring 04 6. Mobility Support on higher layers • Transport layer mobility • Session Initiation Protocol and Mobility Summary & Outlook + Exercises Page 33 Tatiana K. Madsen Hans Peter Schwefel Transport Layer Protocols Goal: data transfer between application (processes) in end-systems • support of multiplexing/de-multiplexing e.g. socket API data stream/connection identified by: two IP addresses, protocol number, two port numbers WCPT: MM3, IP-Mobility Support, Spring 04 Page 34 Tatiana K. Madsen Hans Peter Schwefel Overview: Transport Protocols • User Datagram Protocol UDP (RFC 768) – Connectionless – Unreliable – No flow/congestion control • Transmission Control Protocol TCP (RFC 793, 1122, 1323, 2018, 2581) – Connection-oriented (full duplex) – Reliable, in-order byte-stream delivery – Flow/congestion control • Stream Control Transport Protocol SCTP (see later) • Real-Time Transport Protocol RTP – Uses UDP – Provides: Time-stamps, sequence numbers – Supports: codecs, codec translation, mixing of multi-media streams WCPT: MM3, IP-Mobility Support, Spring 04 Page 35 Tatiana K. Madsen Hans Peter Schwefel • • • Streaming Control Transmission Protocol (SCTP) Defined in RFC2960 (see also RFC 3257, 3286) Purpose initially: Signalling Transport Features – Reliable, full-duplex unicast transport (performs retransmissions) – TCP-friendly flow control (+ many other features of TCP) – Multi-streaming, in sequence delivery within streams Avoid head of line blocking (performance issue) – Multi-homing: hosts with multiple IP addresses, path monitoring (heart-beat mechanism), transparent failover to secondary paths • Useful for provisioning of network reliability SCTP Association IPb1 IPa1 Host A Separate Networks IPa2 WCPT: MM3, IP-Mobility Support, Spring 04 Page 36 Host B IPb2 Tatiana K. Madsen Hans Peter Schwefel Transport Layer Handover in SCTP IP1 AP A IP 2 1. MN communicates with CN via established SCTP association (From IP1 to IP CN) 2. When MN comes in Range of AP B • • AP B Correspondent Node MN obtains new IP address IP2 MN adds IP2 to the existing SCTP association Address configuration Change (ASCONF) Chunk 3. When connection should be transferred to new AP B • • MN sets primary address to IP2 MN deletes old IP1 from SCTP association (ASCONF chunk) WCPT: MM3, IP-Mobility Support, Spring 04 Page 37 Tatiana K. Madsen Hans Peter Schwefel SCTP Mobility support: Discussion • SCTP Handover transparent for network – – No additional network infrastructure needed Possible use-case: switch to peer-to-peer mode without network support • avoids tunneling and tri-angular routing • • Endpoints need to support SCTP (with dynamic control of IP addresses) Signalling to every correspondent node necessary (for every established SCTP association) • • • for high number of parallel connections, large signalling volume over air interface Dynamic Naming Service for connection set-up from CN required (to establish the initial SCTP association) – Dynamic DNS – Other location mechanisms (e.g. based on SIP URLs) Only usable for traffic without real-time requirements (due to SCTP flow/congestion control) – but similar approaches, e.g. for RTP, possible Simultaneous Handover (Mobile Node and Correspondent Node) can lead to loss of connection WCPT: MM3, IP-Mobility Support, Spring 04 Page 38 Tatiana K. Madsen Hans Peter Schwefel Session Initiation Protocol -- SIP SIP: Application layer signalling protocol (RFC 3261) Provides call control for multi-media services initiation, modification, and termination of sessions terminal-type negotiation and selections call holding, forwarding, forking, transfer media type negotiation (also mid-call changes) using Session Description Protocol (SDP) Properties Independent of transport protocols (TCP, UDP, SCTP,…) ASCII format SIP headers Separation of call signalling and data stream Basic Messages (Methods) Responses – – – – – – 1xx Intermediate results e.g. 180 Ringing – 2xx Successful Responses e.g. 200 OK – 3xx Redirections e.g. 302 Moved Temporarily –… INVITE: initiate call ACK: confirm final response (after ‘invite’) BYE: terminate call CANCEL: cancel pending requests OPTIONS: queries features supported by other side – REGISTER: register with location service WCPT: MM3, IP-Mobility Support, Spring 04 Page 39 Tatiana K. Madsen Hans Peter Schwefel SIP Addressing and header format Addressing: • SIP URL (Uniform Resource Locator) • Formats: user@host, user@domain, PhoneNumber@operator, etc. • Examples of SIP URLs: • sip:[email protected] • sip:[email protected] • sip:[email protected] • Example: SIP Header WCPT: MM3, IP-Mobility Support, Spring 04 INVITE sip:[email protected] SIP/2.0 Via: SIP/2.0/UDP 192.168.6.21:5060 From: sip:[email protected] To: <sip:[email protected]> Call-ID: [email protected] CSeq: 100 INVITE Expires: 180 User-Agent: Cisco IP Phone/ Rev. 1/ SIP enabled Accept: application/sdp Contact: sip:[email protected]:5060 Content-Type: application/sdp Page 40 Tatiana K. Madsen Hans Peter Schwefel SIP Call Signalling: Example Proxy Server User Agent INVITE Location/Redirect Server INVITE 302 (Moved Temporarily) User Agent Proxy Server ACK INVITE Call Setup 180 (Ringing) 180 (Ringing) INVITE 180 (Ringing) 200 (OK) ACK 200 (OK) ACK 200 (OK) ACK Media Path Call Teardown RTP MEDIA PATH BYE BYE BYE 200 (OK) 200 (OK) 200 (OK) WCPT: MM3, IP-Mobility Support, Spring 04 Page 41 Tatiana K. Madsen Hans Peter Schwefel SIP: Mobility support MN1 User/Session/Application Mobility (change of terminal) • • • • Registration via SIP ‘REGISTER’ Initial connection set-up between MN1 and CN through ‘INVITE’ mid-session mobility (application mobility): call transfer, SIP method ‘REFER’ (RFC3515) MN2 MN1 Application state could be contained in the message body (‘proprietary’ extension) CN Host Mobility (change of IP address) • • Pre-call: re-register, routing of ‘INVITE’ based on SIPURL mid-call: re-invite WCPT: MM3, IP-Mobility Support, Spring 04 Page 42 MN2 Tatiana K. Madsen Hans Peter Schwefel Summary Approaches: • Separation of host identifier and location identifier • Tunnelling • Soft-state • Performance optimisations: hierarchical/hybrid approaches • [Security requirements and solutions (MACs, encryption, 1. Background: IP, IETF, Mobility & Handover Types 2. Mobile IP (v4): Motivation, Principles, Messages, DHCP 3. MIP Performance aspects & improvements: HMIP, HAWAII, CIP 4. MIP Extensions: Security Aspects (Authentication, Firewall Traversal), Multihoming/flow mobility, IPv6 and MIPv6 sequence numbers, timestamps, nonces)] 5. Mobility support on higher layers: Transport Layer Mobility, Session Initiation Protocol (SIP) WCPT: MM3, IP-Mobility Support, Spring 04 Key Technologies/Protocols: (see left column) Page 43 Tatiana K. Madsen Hans Peter Schwefel Outlook: research topics, IP Mobility • • • Network Mobility Application Mobility (SIP method ‘refer’?) download channel Mobility and QoS (IETF WG NSIS) • Cross layer optimization (L2 triggers, …) • • • MIP and NAT/FW Location-based services and location privacy ‘all IP’ mobile networks WCPT: MM3, IP-Mobility Support, Spring 04 return channel: e.g. GSM Services and applications New radio interface DAB DVB IP based core network cellular GSM IMT-2000 UMTS short range connectivi ty Page 44 Wireline xDSL WLAN type other entities Tatiana K. Madsen Hans Peter Schwefel References • • C. Perkins: ’Mobile IP: Design Principles and Practices.’ Addison-Wesley, 1998. IETF Working groups (see also for RFCs and drafts): – Mobile IP: http://www.ietf.org/html.charters/mobileip-charter.html – IPsec: http://www.ietf.org/html.charters/ipsec-charter.html – IPv6: http://www.ietf.org/html.charters/ipv6-charter.html – • • • • Others: nemo, mip4, dhcp, seamoby J. Schiller: ’Mobile Communications’. Addison-Wesley, 2000. A. Festag, ‘Mobile Internet II, Overview of current mobility approaches’ (lecture material). TU Berlin, 2002. Seok Joo Koh, ‘mSCTP: Use of SCTP for IP Mobility Support’, Presentation, IT Forum, Korea, 2003 H. Schulzrinne, E. Wedlund, ‘Application-Layer Mobility Using SIP’. Mobile Computing and Communications Review, Vol. 1, No. 2 WCPT: MM3, IP-Mobility Support, Spring 04 Page 45 Tatiana K. Madsen Hans Peter Schwefel Acknowledgements • Lecture notes: Mobile Communciations, Jochen Schiller, www.jochenschiller.de • Student work (all TU Munich) – – – – Stefan Rank (Master Thesis) Michael Zech (Seminar) Krasimir Dzhigovechki (Seminar) Wolfgang Thomas (Seminar) • Lecture notes: Wireless communication protocols (R. Prasad, TKM) • Tutorial: Voice over IP Protocols – An Overview, www.vovida.org • Tutorial: IP Technology in 3rd Generation mobile networks, Siemens AG (J. Kross, L. Smith, H. Schwefel) WCPT: MM3, IP-Mobility Support, Spring 04 Page 46 Tatiana K. Madsen Hans Peter Schwefel