1	Course Overview Introduction Data in Wireless Cellular Systems Data in Wireless Local Area Networks Internet Protocols TCP over Wireless Link Ad-Hoc Networks, Sensor Networks Services and Service Discovery System Support for Mobile Applications
2	What is TCP/IP ? TCP/IP is a collection of protocols that facilitates communications among servers and terminals that are hooked to different networks
3	What is TCP/IP ? (continue) The TCP and IP are only two of several protocols, but the name stuck !! They are the most important ones
4	The Big Picture of TCP/IP
5	IETF: Internet Engineering Task Force Who develops protocols such as TCP/IP, Mobile IP, ...? “standardized” by action of IETF IETF has over 70 working groups considering a broad range of protocol proposals for the Internet, tries to identify protocol needs in advance (?) IETF works with Internet Assigned Number Authority (IANA) to keep track of protocol number assignments and address allocations as required by various Internet protocols each protocol specified by a “Request for Comments” working groups develop new RFCs by publishing Internet Drafts, building prototypes, and encouraging public debate operational model: rough consensus and running code
6	IP Addresses
7	IP Addresses and Physical Addresses Map IP addresses into physical addresses destination host next hop router Techniques encode physical address in host part of IP address table-based ARP table of IP to physical address bindings broadcast request if IP address not in table target machine responds with its physical address table entries are discarded if not refreshed
8	IPv6 Extended addressing capabilities: 128-bit address field and other improvements. Simplified header format: Some fields of IPv4 are dropped or turned into options Improved support for extensions and options: flexibility and ability to introduce new options Flow labeling Authentication and privacy
9	Why Worry About Mobility? mobile computing is on the rise wireless communications technologies widely available IEEE 802.11 finally standardized MAC layer protocol with lots of features: power saving, ad-hoc networking support, maybe even isochronous communication cellular telephony everywhere AMPS and CDPD GSM wireless indoor equipment (IR and RF) people expect the same from both desktop and laptop high-resolution color display 200 MHz processor multi-gigabyte disk with a docking station, the laptop is the desktop
10	Why Worry about Mobility? wireless communication and powerful portable devices lead to new computing paradigms: mobile computing ubiquitous computing nomadic computing at the same time, the Internet and in particular the Web, are growing exponentially timely news (and lots of it), user-friendly(?), lots of pretty pictures (70%-80% of Internet traffic is WWW traffic) the “Information Superhighway” is where people want to be certainly strong support by national governments to build and maintain this infrastructure mobile computing seen as “on-ramp” to this infrastructure
11	Where to Solve Mobility Problem What model of mobility “nomadic clients”: DHCP or similar solutions enough Truly mobile: need to keep connections alive WHILE moving Where in the protocol stack IP is common glue, solve it once and for all at IP layer BUT: may be in contradiction to end-to-end argument Other solutions/proposals exits, such as TCP connection migration
12	Motivation for Mobile IP Routing based on IP destination address, network prefix (e.g. 129.13.42) determines physical subnet change of physical subnet implies change of IP address to have a topological correct address (standard IP) or needs special entries in the routing tables Specific routes to end-systems? change of all routing table entries to forward packets to the right destination does not scale with the number of mobile hosts and frequent changes in the location, security problems Changing the IP-address? adjust the host IP address depending on the current location almost impossible to find a mobile system, DNS updates take to long time TCP connections break, security problems
13	Requirements to Mobile IP (RFC 3344, was: 3220, was: 2002) Transparency mobile end-systems keep their IP address continuation of communication after interruption of link possible point of connection to the fixed network can be changed Compatibility support of the same layer 2 protocols as IP no changes to current end-systems and routers required mobile end-systems can communicate with fixed systems Security authentication of all registration messages Efficiency and scalability only little additional messages to the mobile system required (connection typically via a low bandwidth radio link) world-wide support of a large number of mobile systems in the whole Internet
14	Terminology Mobile Node (MN) system (node) that can change the point of connection to the network without changing its IP address Home Agent (HA) system in the home network of the MN, typically a router registers the location of the MN, tunnels IP datagrams to the COA Foreign Agent (FA) system in the current foreign network of the MN, typically a router forwards the tunneled datagrams to the MN, typically also the default router for the MN Care-of Address (COA) address of the current tunnel end-point for the MN (at FA or MN) actual location of the MN from an IP point of view can be chosen, e.g., via DHCP Correspondent Node (CN) communication partner
15	Example Network
16	Data Transfer to the Mobile System
17	Data Transfer from the Mobile System
18	Network Integration Agent Advertisement HA and FA periodically send advertisement messages into their physical subnets MN listens to these messages and detects, if it is in the home or a foreign network (standard case for home network) MN reads a COA from the FA advertisement messages Registration (always limited lifetime!) MN signals COA to the HA via the FA, HA acknowledges via FA to MN these actions have to be secured by authentication Advertisement HA advertises the IP address of the MN (as for fixed systems), i.e. standard routing information routers adjust their entries, these are stable for a longer time (HA responsible for a MN over a longer period of time) packets to the MN are sent to the HA, independent of changes in COA/FA
19	Agent Advertisement
20	Registration
21	Mobile IP Registration Request
22	Mobile IP Registration Reply
23	Encapsulation
24	Encapsulation I Encapsulation of one packet into another as payload e.g. IPv6 in IPv4 (6Bone), Multicast in Unicast (Mbone) here: e.g. IP-in-IP-encapsulation, minimal encapsulation or GRE (Generic Record Encapsulation) IP-in-IP-encapsulation (mandatory, RFC 2003) tunnel between HA and COA
25	Encapsulation II Minimal encapsulation (optional) avoids repetition of identical fields e.g. TTL, IHL, version, DS (RFC 2474, old: TOS) only applicable for unfragmented packets, no space left for fragment identification
26	Optimization of Packet Forwarding Triangular Routing sender sends all packets via HA to MN higher latency and network load “Solutions” sender learns the current location of MN direct tunneling to this location HA informs a sender about the location of MN big security problems! Change of FA packets on-the-fly during the change can be lost new FA informs old FA to avoid packet loss, old FA now forwards remaining packets to new FA this information also enables the old FA to release resources for the MN
27	Change of Foreign Agent
28	Reverse Tunneling (RFC 3024, was: 2344)
29	Mobile IP with Reverse Tunneling Router accept often only “topological correct“ addresses (firewall!) a packet from the MN encapsulated by the FA is now topological correct furthermore multicast and TTL problems solved (TTL in the home network correct, but MN is too far away from the receiver) Reverse tunneling does not solve problems with firewalls, the reverse tunnel can be abused to circumvent security mechanisms (tunnel hijacking) optimization of data paths, i.e. packets will be forwarded through the tunnel via the HA to a sender (double triangular routing) The standard is backwards compatible the extensions can be implemented easily and cooperate with current implementations without these extensions Agent Advertisements can carry requests for reverse tunneling
30	Mobile IP and IPv6 Mobile IP was developed for IPv4, but IPv6 simplifies the protocols security is integrated and not an add-on, authentication of registration is included COA can be assigned via auto-configuration (DHCPv6 is one candidate), every node has address autoconfiguration no need for a separate FA, all routers perform router advertisement which can be used instead of the special agent advertisement; addresses are always co-located MN can signal a sender directly the COA, sending via HA not needed in this case (automatic path optimization) „soft“ hand-over, i.e. without packet loss, between two subnets is supported MN sends the new COA to its old router the old router encapsulates all incoming packets for the MN and forwards them to the new COA authentication is always granted
31	Problems with Mobile IP Security authentication with FA problematic, for the FA typically belongs to another organization no protocol for key management and key distribution has been standardized in the Internet patent and export restrictions Firewalls typically mobile IP cannot be used together with firewalls, special set-ups are needed (such as reverse tunneling) QoS many new reservations in case of RSVP tunneling makes it hard to give a flow of packets a special treatment needed for the QoS Security, firewalls, QoS etc. are topics of current research and discussions!
32	IP Micro-Mobility Support Micro-mobility support: Efficient local handover inside a foreign domain without involving a home agent Reduces control traffic on backbone Especially needed in case of route optimization Example approaches: Cellular IP HAWAII Hierarchical Mobile IP (HMIP) Important criteria: Security Efficiency, Scalability, Transparency, Manageability
33	Cellular IP Operation: „CIP Nodes“ maintain routing entries (soft state) for MNs Multiple entries possible Routing entries updated based on packets sent by MN CIP Gateway: Mobile IP tunnel endpoint Initial registration processing Security provisions: all CIP Nodes share „network key“ MN key: MD5(net key, IP addr) MN gets key upon registration
34	Cellular IP: Evaluation Advantages: Simple and elegant architecture Mostly self-configuring (little management needed) Integration with firewalls / private address support possible Potential problems: Not transparent to MNs (additional control messages) Public-key encryption of MN keys may be a problem for resource-constrained MNs Multiple-path forwarding may cause inefficient use of available bandwidth
35	HAWAII Operation: MN obtains co-located COA and registers with HA Handover: MN keeps COA, new BS answers Reg. Request and updates routers MN views BS as foreign agent Security provisions: MN-FA authentication mandatory Challenge/Response Extensions mandatory
36	HAWAII: Evaluation Advantages: Mostly transparent to MNs (MN sends/receives standard Mobile IP messages) Explicit support for dynamically assigned home addresses Potential problems: Mixture of co-located COA and FA concepts may not be supported by some MN implementations No private address support possible because of co-located COA
37	Hierarchical Mobile IPv6 (HMIPv6) Operation: Network contains mobility anchor point (MAP) mapping of regional COA (RCOA) to link COA (LCOA) Upon handover, MN informs MAP only gets new LCOA, keeps RCOA HA is only contacted if MAP changes Security provisions: no HMIP-specific security provisions binding updates should be authenticated
38	Hierarchical Mobile IP: Evaluation Advantages: Handover requires minimum number of overall changes to routing tables Integration with firewalls / private address support possible Potential problems: Not transparent to MNs Handover efficiency in wireless mobile scenarios: Complex MN operations All routing reconfiguration messages sent over wireless link