1 Gateway MSC (GMSC) Connects mobile network to a fixed networkEntry point to a PLMN Usually one per PLMN Request routing information from the HLR and routes the connection to the local MSC Dedicated Gateway MSCs (GMSCs) are available to pass voice traffic between fixed networks and mobile network. GMSC queries the database (HLR ) and routes the connection to the local MSC in whose area the mobile station is currently staying. Sridhar Iyer IIT Bombay
2 Air Interface: Physical ChannelUplink/Downlink of 25MHz MHz for Up link MHz for Down link Combination of frequency division and time division multiplexing FDMA 124 channels of 200 kHz 200 kHz guard band TDMA Burst Modulation used Gaussian Minimum Shift Keying (GMSK) On the physical layer GSM uses a combination of FDMA and TDMA for multiple access. Two frequency bands 45 Mhz apart have been reserved for GSM operation: MHz for transmission from MS to BTS (Uplink) and MHz for transmission from BTS to MS (Down link). Each of these bands of 25 MHz width is divided into 124 single carrier channels of 200 kHz width. In each of the up-link / down-link bands there is a guard-band of 200 kHz. This variant of FDMA is also called Multi-Carrier(MC). Each Radio Frequency Channel (RFCH) is uniquely numbered, and a pair of channels with the same number forms a duplex channel with a duplex distance of 45 MHz. The modulation used for coding is GSMK. Sridhar Iyer IIT Bombay
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4 Bursts Building unit of physical channel Types of bursts NormalSynchronization Frequency Correction Dummy Access Sridhar Iyer IIT Bombay
5 Normal Burst Normal Burst2*(3 head bit + 57 data bits + 1 signaling bit) + 26 training sequence bit guard bit Used for all except RACH, FSCH & SCH The normal burst is used to transmit information on traffic and control (except RACH) channels. The bursts are separated through guard bands. At the start and end of each burst are three tail bits which are always set to logical "0". These bits fill a short t ime span during which transmitter power is ramped up or down and during which no data transmission is possible. The Stealing Flags (SF) are signalling bits which indicate whether the burst contains traffic data or signalling data. A normal burst contains besides the synchronization and signalling bits two blocks of 57 bits each of error-protected and channel encoded user data separated by a 26-bit midamble. This midamble consists of predefined, known bit patterns, the training sequences (discussed in detail later), which are used for channel estimation to optimize reception with an equalizer and for synchronization. With the help of these training sequences, the equalizer eliminates or reduces the intersymbol interferences which are caused by propogation time difference of the multipath propogation. Sridhar Iyer IIT Bombay
6 Air Interface: Logical ChannelTraffic Channel (TCH) Signaling Channel Broadcast Channel (BCH) Common Control Channel (CCH) Dedicated/Associated Control Channel (DCCH/ACCH) A great variety of information is transmitted between the BTS and the MS. Depending on the kind of information transmitted different logical channel is made. Logical Channels are divided into two categories. TCHs and Control Channels TCHs are intended to carry either encoded speech or user data. A full rate (TCH/F), Bm, carries information at a gross rate of 22.8 kbps. The raw data rate for speech is 13kbps. A half rate (TCH/H), Lm, carries information at a gross rate of 11.4 kbps. Signalling /Control channels are intended to carry signalling or synchronization data. Three kinds have been defined: BCCH: Is intended to broadcast variety of information from BTS to all the MSs (Unidirectional). CCCH: It is bidirectional point to multipoint control channel that is primarily used for access management. DCCH:It is point to point directional control channel. Are of two types namely Standalone Dedicated and Associated. Sridhar Iyer IIT Bombay
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8 Traffic Channel Transfer either encoded speech or user dataBidirectional Full Rate TCH Rate 22.4kbps Bm interface Half Rate TCH Rate 11.2 kbps Lm interface Sridhar Iyer IIT Bombay
9 Full Rate Speech CodingSpeech Coding for 20ms segments 260 bits at the output Effective data rate 13kbps Unequal error protection 182 bits are protected bits = 182 bits 78 bits unprotected Channel Encoding Codes 260 bits into (8 x 57 bit blocks) 456 bits Interleaving 2 blocks of different set interleaved on a normal burst (save damages by error bursts) Basic speech is sensed by a coder for 20ms segments and it produces 260 bits at the output. Thus the output data rate of the speech coder is 13kbps. The residual data consisting of 182 bits and 78 bits of side information when passed through the half rate convolutional encoder provides 456 bits of coded data. Hence at every 20 ms the channel coder releases 456 bits. The resulting 456 bit is then transmitted using an interleaving scheme. The interleaving depth is eight. This means that eight frames are used to transmit these bits. REFER THE CHART IN THE NEXT SLIDE Sridhar Iyer IIT Bombay
10 Speech 20 ms 20 ms Speech Coder Speech Coder 260 260 Channel Encoding456 bit 456 bit Interleaving 1 2 3 4 5 6 7 8 NORMAL BURST 3 57 1 26 1 57 3 8.25 Sridhar Iyer IIT Bombay Out of first 20 ms Out of second 20ms
11 Traffic Channel Structure for Full Rate Coding2 3 4 1 8 7 6 5 9 10 11 12 13 14 15 16 17 26 T S I Slots Bursts for Users allocated in Slot T = Traffic S = Signal( contains information about the signal strength in neighboring cells) T Sridhar Iyer IIT Bombay
12 Traffic Channel Structure for Half Rate Coding2 3 4 1 8 7 6 5 9 10 11 12 13 14 15 16 17 26 T S Slots Burst for one users T = Bursts for another users allocated in alternate Slots T T Traffic Channel Structure for Half Rate Coding Sridhar Iyer IIT Bombay
13 BCCH Broadcast Control Channel (BCCH) BTS to MSRadio channel configuration Current cell + Neighbouring cells Synchronizing information Frequencies + frame numbering Registration Identifiers LA + Cell Identification (CI) + Base Station Identity Code (BSIC) The BCCH provides general information on a per-BTS basis (cell-specific information) including information necessary for the MS to register in the system. After intially accessing the mobile, the BTS calculates the required MS power level and send a set of power commands on this channel. Other information sent over this channel includes country code, network code, local area code, PLMN code, RF channels used within the cell, in the surrounding cells, hopping sequence number,mobile RF channel number for allocation, cell selection parameters, and RACH description. An important message on BCCH is organisation of CCCH. This is transmitted on a designated RF carrier using timeslot 0, denoted as C0T0. This channel is never kept idle- either the relevant messages are sent or dummy burst is sent. Other channels that belong to this group are the FCH and SCH. Sridhar Iyer IIT Bombay
14 FCCH & SCH Frequency Correction Channel Synchronization ChannelRepeated broadcast of FB Synchronization Channel Repeated broadcast of SB Message format of SCH The FCCH carries information for frequency correction of the MS downlink. It is required for the correct operation of a radio subsytem. Similar to BCCH this is also for point to multipoint communication. This allows MS to accurately tune to a BTS. The SCH carries information for the frame synchronization (TDMA-frame number) of the MS and the identificationof the BTS. The SCH carries a 64 bit binary sequence that is a priori know to the MS. By correlating these bits with the internally stored 64 bits, MS achieves the exact timing with respect to a GSM frame. The layout of SCH message is shown. It contains two encoded parameters: 1) BTS Identification Code (BSIC) and (2) Reduced TDMA Frame Number (RFN). FCCH and BCH cann't be frequency hopped, as these channel carry synchronization and system-related information whose exact location must be known to MS. PLMN color 3 bits BS color T1 Superframe index 11 bits T2 multiframe T3 block frame index 3bits Sridhar Iyer IIT Bombay
15 RACH & SDCCH Random Access Channel (RACH)MS to BTS Slotted Aloha Request for dedicated SDCCH Standalone Dedicated Control Channel (SDCCH) MS BTS Standalone; Independent of TCH RACH is an uplink channel and operates in point to point mode from MS to BTS. It is used by MS to request allocation of an SDCCH either as a page response or for call originating/registration of MS. The channel operates on slotted Aloha protocol and thus the contention possibilty exists. If the MS request is not answered within a specified time, the MS assumes that a collision has occurred and repeats the request. Sridhar Iyer IIT Bombay
16 AGCH & PCH Access Grant Channel (AGCH) Paging Channel (PCH) BTS to MSAssign an SDCCH/TCH to MS Paging Channel (PCH) Page MS AGCH is used tp allocate an SDCCH or a TCH directly to an MS. PCH is used to page (search) a MS. It is in downlink direction. A combined paging and access grant channel is designated as PAGCH. Sridhar Iyer IIT Bombay
17 SACCH & FACCH Slow Associated Control Channel (SACCH)MS BTS Always associated with either TCH or SDCCH Information Optimal radio operation; Commands for synchronization Transmitter power control; Channel measurement Should always be active; as proof of existence of physical radio connection Fast Associated Control Channel (FACCH) Handover Pre-emptive multiplexing on a TCH, Stealing Flag (SF) It is a dedicated channel allocation of which is linked with either TCH or SDCCH. It is a continuous data channel carrying information for the optimal operation of the radio channel, e.g.commands for synchronization and transmitter power control and report on channel measurement. This is a necessary channel for mobile assisted hand-over function. The channel is also used for time alignment and is meant for both the uplink and downlink. It is used for point-to-point communication between the MS and BTS. Data must be sent continuously over the SACCH since the arrival of SACCH packet is taken as a proof of the existence of the physical radio connection. When there is no signalling data, the MS send a measurement report with the current results of the continuously conducted radio signal level measurement. Sridhar Iyer IIT Bombay
18 Example: Incoming Call SetupMS BSS/MSC Paging request (PCH) MS BSS/MSC Channel request (RACH) MS BSS/MSC Immediate Assignment (AGCH) MS BSS/MSC Paging Response (SDCCH) MS BSS/MSC Authentication Request (SDCCH) MS BSS/MSC Authentication Response (SDCCH) MS BSS/MSC Cipher Mode Command (SDCCH) MS BSS/MSC Cipher Mode Compl (SDCCH) MS BSS/MSC Setup (SDCCH) MS BSS/MSC Call Confirmation (SDCCH) MS BSS/MSC Assignment Command (SDCCH) MS BSS/MSC Assignment Compl. (FACCH) MS BSS/MSC Alert (FACCH) MS BSS/MSC Connect (FACCH) MS BSS/MSC Connect Acknowledge (FACCH) MS BSS/MSC Data (TCH) The figure shows an example of incoming call connection setup at the air interface how the various logical channels are used in principle. The MS is called via the PCH and requests a signaling channel on the RACH. It gets SDCCH through an IMMEDIATE ASSIGNMENT message on the AGCH. Then follow authentication, start of ciphering, and start of setup over the SDCCH. An ASSIGNMENT COMMAND message gives the traffic channel to the MS, which acknowledges its receipt on the FACCH of the traffic channel. The FACCH is also used to continue the connection setup. Sridhar Iyer IIT Bombay
19 Sridhar Iyer IIT Bombay Select the channel with highest RF level amongthe control channels Power On Scan Channels, monitor RF levels Scan the channel for the FCCH Select the channel with next highest Rf level from the control list. NO Is FCCH detected? YES Scan channel for SCH NO Is SCH detected? YES Read data from BCCH and determine is it BCCH? NO From the channel data update the control channel list Is the current BCCH channel included? YES Camp on BCCH and start decoding Sridhar Iyer IIT Bombay
20 Adaptive Frame SynchronizationTiming Advance Advance in Tx time corresponding to propagation delay 6 bit number used; hence 63 steps 63 bit period = 233 micro seconds (round trip time) 35 Kms The MS can be any where within a cell, which means the distance between MS and BTS may vary and hence the signal propogation time. Due to this the burst received at the BTS would be offset. Since TDMA is based on the exact synchronization of transmitted and received data burst it cannot tolerate any time shifts. i.e. burst transmitted by different MS in adjacent time slots must not overlap when received at the BTS by more than the guard period. To avoid such collisions, the start of transmission time from the MS is advanced in proportion to the distance from the BTS. The process of adapting the transmissions from the MS to the TDMA frame is called adaptive frame alignment. To denote the timing advance 7 bits are used. The unit of it is one bit period (3.69 microsecond). The maximum time period value of 63 correspond to 63x3.69 = 232 micro second. This is the round trip time hence one way time available = 232/2 =116 micro second. This corresponds to a maximum distance between MS and BTS of 35 km. Sridhar Iyer IIT Bombay
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22 GSM: Channel Mapping SummaryLogical channels Traffic Channels; Control Channels Physical Channel Time Slot Number; TDMA frame; RF Channel Sequence Mapping in frequency 124 channels, 200KHz spacing Mapping in time TDMA Frame, Multi Frame, Super Frame, Channel Two kinds of multiframe: 26-frame multiframe; usage -Speech and Data 51-frame multiframe; usage -Signalling The mapping of logical onto physical channels has two components: a) mapping in frequency b) mapping in time. The mapping of a logical channel onto a physical channel in the frequency domain is based on the TDMA frame number RFN and the frequencies allocated to base and MS. In the time domain, the logical channels are organized by the definition of complex superstructures on top of the TDMA frames, formimg so-called multiframes, superframes and hyperframes. For the mapping of logical onto physical channels, one is interested in the multiframe doamin. These multiframes allow one to map (logical) subchannels onto physical channels. Two kinds of multiframe are defined: a multiframe consisting of 26 TDMA frames (predominantly payload - speech and data frames) and a multi frame of 51 TDMA frames (predominantly signaling frames) Sridhar Iyer IIT Bombay
23 1 2 3 2045 2046 2047 1 2 3 50 1 2 25 3 23 24 T12 (SACCH) T23 I 1 49 T0 T1 T2 2 3 50 The data of FACCH is transmitted by occupying one half of the bits in eight consecutive bursts, by stealling these bits from the TCH. For this purpose, the Stealing Flags of the bursts are set. Gross Data Rate = Rate for Signaling, Synchronization, Guard Period + Rate for User Data (coded and enciphered) + Rate for SACCH and IDLE. 33.9 kbps = 9.2 kbps kbps +1.9 kbps Each 51 consecutive time slots of a TDMA frame form a multiframe to form the structure for the transmission of the control channels which are not associated with a TCH ( all except FACCH and SACCH). 1 2 3 4 5 6 7 Sridhar Iyer IIT Bombay
24 Outline Introduction and Overview Wireless LANs: IEEE 802.11Mobile IP routing TCP over wireless GSM air interface GPRS network architecture Wireless application protocol Mobile agents Mobile ad hoc networks Sridhar Iyer IIT Bombay
25 GSM architecture Sridhar Iyer IIT Bombay Source: Bettstetter et. al.
26 GSM multiple access Sridhar Iyer IIT Bombay
27 GSM call routing Sridhar Iyer IIT Bombay 1. MSISDN 2. MSISDN VLR HLRAUC EIR GMSC/I WF MSC BSC BTS ISDN 3. MSRN 4. MSRN 5. MSRN 6. TMSI 7. TMSI 8. TMSI LA2 LA1 MS The principal sequence of oprerations for routing to a mobile subscriber is shown in the diagram. The number dialed to reach a mobile subscriber (MSISDN) contains no information at all about the current location of the subscriber. Inorder to establish a complete connection to a mobile subscriber, however, one must determine the current location and the locally responsible switch (MSC). In order to be able to route the call to this switch, the routing address to this subscriber ( MSRN) has to be obtained. This routing address is assigned temporarily to a subscriber by its currently associated VLR. The steps envolved are: (1) An ISDN switch recognizes from the MSISDN that the called subscriber is a mobile subscriber and therefore can forward the call to the GMSC of the subscribers home PLMN based on the CC and the NDC in the MSISDN. (2,3) This GMSC can now request the current routing address (MSRN) for the mobile subscriber from the HLR( using MAP) (4) By way of MSRN the call is forwarded to the local MSC (5,6) This MSC than determine the TMSI of the subscriber (7) MSC then intiate paging request in the relevant LA.(8) After the mobile station has responded to the paging call, the connectin can be switched through. Sridhar Iyer IIT Bombay
28 Options for data transferTwo enhancements to GSM for data HSCSD - High Speed Circuit Switched Data GPRS - General Packet Radio Service Both have capacity to use new coding schemes and to make multislot allocation GPRS, being a packet switched service, is known to be more efficient and flexible for data transfer purposes It delivers circuit and packet-switched services in one mobile radio network Sridhar Iyer IIT Bombay
29 GPRS features Radio resources are allocated for only one or a few packets at a time, so GPRS enables many users to share radio resources, and allow efficient transport of packets fast setup/access times connectivity to external packet data n/w volume-based charging GPRS also carries SMS in data channels rather than signaling channels as in GSM Sridhar Iyer IIT Bombay
30 GPRS Architecture Sridhar Iyer IIT Bombay
31 GPRS Architecture Requires addition of a new class of nodes called GSNs (GPRS Support Nodes) SGSN: Serving GPRS Support Node, GGSN: Gateway GPRS Support Node BSC requires a PCU (Packet Control Unit) and various other elements of the GSM n/w require software upgrades All GSNs are connected via an IP-based backbone. Protocol data units (PDUs) are encapsulated and tunneled between GSNs Sridhar Iyer IIT Bombay
32 GGSN Serves as the interface to external IP networks which see the GGSN as an IP router serving all IP addresses of the MSs GGSN stores current SGSN address and profile of the user in its location register It tunnels protocol data packets to and from the SGSN currently serving the MS It also performs authentication and charging GGSN can also include firewall and packet-filtering mechanisms Sridhar Iyer IIT Bombay
33 SGSN Analog of the MSC in GSMRoutes incoming and outgoing packets addressed to and from any GPRS subscriber located within the geographical area served by the SGSN Location Register of the SGSN stores information (e.g. current cell and VLR) and user profiles (e.g. IMSI, addresses) of all GPRS users registered with this SGSN Sridhar Iyer IIT Bombay
34 BSC and others BSC must get a Packet Control Unit toset up, supervise and disconnect packet-switched calls also support cell change, radio resource configuration and channel assignment MSC/VLR, HLR and SMS Center must be enhanced for interworking with GPRS MS must be equipped with the GPRS protocol stack Sridhar Iyer IIT Bombay
35 HLR - Home Location RegisterShared database, with GSM Is enhanced with GPRS subscriber data and routing information For all users registered with the network, HLR keeps user profile, current SGSN and Packet Data Protocol (PDP) address(es) information SGSN exchanges information with HLR e.g., informs HLR of the current location of the MS When MS registers with a new SGSN, the HLR sends the user profile to the new SGSN Sridhar Iyer IIT Bombay
36 MSC/VLR-Visitor Location RegisterVLR is responsible for a group of location areas. It stores data of only those users in its area of responsibility MSC/VLR can be enhanced with functions and register entries that allow efficient coordination between GPRS and GSM services combined location updates combined attachment procedures Sridhar Iyer IIT Bombay
37 GPRS Transmission PlaneSridhar Iyer IIT Bombay
38 Air Interface Um Is one of the central aspects of GPRSConcerned with communication between MS and BSS at the physical, MAC and RLC layers Physical channel dedicated to packet data traffic is called a packet data channel (PDCH) Capacity on Demand: Allocation/Deallocation of PDCH to GPRS traffic is dynamic BSC controls resources in both directions No conflicts on downlink Conflicts in uplink are resolved using slotted ALOHA Sridhar Iyer IIT Bombay
39 Data transfer between MS and SGSNSNDCP transforms IP/X.25 packets into LLC frames, after optional header/data compression, segmentation and encryption Maximum LLC frame size is 1600 bytes An LLC frame is segmented into RLC data blocks which are coded into radio blocks Each radio block comprises four normal bursts (114 bits) in consecutive TDMA frames RLC is responsible for transmission of data across air-interface, including error correction MAC layer performs medium allocation to requests, including multi-slot allocation PHY layer is identical to GSM Sridhar Iyer IIT Bombay
40 Data transfer between GSNsAlthough the GPRS network consists of several different nodes, it represents only one IP hop GTP enables tunneling of PDUs between GSNs, by adding routing information Below GTP, TCP/IP and IP are used as the GPRS backbone protocols Sridhar Iyer IIT Bombay
41 MS - state model In Idle State MS is not reachableWith GPRS Attach MS moves into ready state With Detach, it returns to Idle state: all PDP contexts are deleted Standby state is reached when MS does not send data for a long period and ready timer expires Sridhar Iyer IIT Bombay
42 GPRS – PDP context MS gets a packet temporary mobile subscriber identity (p-TMSI) during Attach MS requests for one or more addresses used in the packet data network, e.g. IP address GGSN creates a PDP context for each session PDP type (IPV4), PDP address (IP) of MS, requested quality of service (QoS) and address of GGSN PDP context is stored in MS, SGSN and GGSN Mapping between the two addresses, enables GGSN to transfer packets between MS and the PDN Sridhar Iyer IIT Bombay
43 GPRS - Routing Sridhar Iyer IIT Bombay
44 GPRS - Routing MS from PLMN-2 is visiting PLMN-1.IP address prefix of MS is the same as GGSN-2 Incoming packets to MS are routed to GGSN-2 GGSN-2 queries HLR and finds that MS is currently in PLMN-1 It encapsulates the IP packets and tunnels them through the GPRS backbone to the appropriate SGSN of PLMN-1 SGSN decapsulates and delivers to the MS Sridhar Iyer IIT Bombay
45 GPRS Summary Enables many users to share radio resources by dynamic, on-demand, multi-slot allocation Provides connectivity to external packet data networks Modification to the GSM air-interface Addition of new GPRS Support Nodes Assignment of PDP context to MS Enables volume-based charging as well as duration based charging Sridhar Iyer IIT Bombay
46 Outline Introduction and Overview Wireless LANs: IEEE 802.11Mobile IP routing TCP over wireless GSM air interface GPRS network architecture Wireless application protocol Mobile agents Mobile ad hoc networks Sridhar Iyer IIT Bombay
47 Variability of the mobile environmentMobility stationary nomadic (pedestrian speed) mobile (vehicular speed) roaming (mobile across networks) Connectivity connected semi-connected (asymmetric) disconnected Mobile Device Capability form factor GUI multimedia real-time multimedia Sridhar Iyer IIT Bombay
48 Wireless Application Protocol (WAP)HTTP/HTML have not been designed for mobile devices and applications WAP empowers mobile users with wireless devices to easily access and interact with information and services. A “standard” created by wireless and Internet companies to enable Internet access from a cellular phone Sridhar Iyer IIT Bombay
49 Why is HTTP/HTML not enough?Big pipe - small pipe syndrome Wireless network 50 WHY WAP? Wireless networks and phones WAPhave specific needs and requirements not addressed by existing Internet technologies WAP Enables any data transport TCP/IP, UDP/IP, GUTS (IS-135/6), SMS, or USSD. Optimizes the content and air-link protocols Utilizes plain Web HTTP 1.1 servers utilizes standard Internet markup language technology (XML) all WML content is accessed via HTTP 1.1 requests WML UI components map well onto existing mobile phone UI no re-education of the end-users leveraging market penetration of mobile devices Sridhar Iyer IIT Bombay 51 WAP: main features Browser Markup language Script language Gateway“Micro browser”, similar to existing web browsers Markup language Similar to HTML, adapted to mobile devices Script language Similar to Javascript, adapted to mobile devices Gateway Transition from wireless to wired world Server “Wap/Origin server”, similar to existing web servers Protocol layers Transport layer, security layer, session layer etc. Telephony application interface Access to telephony functions Sridhar Iyer IIT Bombay 52 Internet model HTML HTTP TLS/SSL TCP/IP Sridhar Iyer IIT Bombay 53 WAP architecture Web Server WAP Gateway Client HTTP WSP/WTPContent CGI Scripts etc. with WML-Script WML Decks WAP Gateway WML Encoder WMLScript Compiler Protocol Adapters Client WML WML-Script WTAI Etc. HTTP WSP/WTP Sridhar Iyer IIT Bombay Source: WAP Forum 54 WAP application serverClient WML WML-Script WTAI Etc. WAP Application Server WML Encoder WMLScript Compiler Protocol Adapters Application Logic WSP/WTP with WML-Script WML Decks Content Sridhar Iyer IIT Bombay Source: WAP Forum 55 WAP specifies Wireless Application Environment Wireless Protocol StackWML Microbrowser WMLScript Virtual Machine WMLScript Standard Library Wireless Telephony Application Interface (WTAI) WAP content types Wireless Protocol Stack Wireless Session Protocol (WSP) Wireless Transport Layer Security (WTLS) Wireless Transaction Protocol (WTP) Wireless Datagram Protocol (WDP) Wireless network interface definitions Sridhar Iyer IIT Bombay 56 WAP stack WAE (Wireless Application Environment):Architecture: application model, browser, gateway, server WML: XML-Syntax, based on card stacks, variables, ... WTA: telephone services, such as call control, phone book etc. WSP (Wireless Session Protocol): Provides HTTP 1.1 functionality Supports session management, security, etc. Sridhar Iyer IIT Bombay 57 WAP stack (contd.) WTP (Wireless Transaction Protocol):Provides reliable message transfer mechanisms Based on ideas from TCP/RPC WTLS (Wireless Transport Layer Security): Provides data integrity, privacy, authentication functions Based on ideas from TLS/SSL WDP (Wireless Datagram Protocol): Provides transport layer functions Based on ideas from UDP Content encoding, optimized for low-bandwidth channels, simple devices Sridhar Iyer IIT Bombay 58 WDP: Wireless Datagram ProtocolGoals create a worldwide interoperable transport system by adapting WDP to the different underlying technologies transmission services, such as SMS in GSM might change, new services can replace the old ones WDP Transport layer protocol within the WAP architecture uses the Service Primitive T-UnitData.req .ind uses transport mechanisms of different bearer technologies offers a common interface for higher layer protocols allows for transparent communication despite different technologies addressing uses port numbers WDP over IP is UDP/IP Sridhar Iyer IIT Bombay 59 WDP: service primitivesT-SAP T-DUnitdata.req (DA, DP, SA, SP, UD) T-DUnitdata.ind (SA, SP, UD) T-DError.ind (EC) SAP: Service Access Point DA: Destination Address DP: Destination Port SA: Source Address SP: Source Port UD: User Data EC: Error Code Sridhar Iyer IIT Bombay Source: Schiller 60 Service, Protocol, Bearer: ExampleWAP Over GSM Circuit-Switched RAS - Remote Access Server IWF - InterWorking Function WSP WAE Subnetwork IP Apps on Other Servers WAP Proxy/Server CSD-RF PPP Mobile IWF PSTN Circuit ISP/RAS WTP UDP Any bearer which supports IP will be able to support WTP since WTP/T and in future WTP/C is defined for operation over UDP. The WTP/D service is UDP/IP. Note: UDP will require a new port number to be issued/reserved by IANA for WAP. After which the suite of WAP protocols will be distinguished by port numbers or protocol identifiers defined by the WAP Forum within the WAP UDP port number issued by IANA. Sridhar Iyer IIT Bombay Source: WAP Forum 61 Service, Protocol, Bearer: ExampleWAP Over GSM Short Message Service WAP Proxy/Server Mobile WAE WAE Apps on other servers WSP WSP SMSC WTP WTP WDP WDP SMS SMS WDP Tunnel Protocol WDP Tunnel Protocol Subnetwork Subnetwork Sridhar Iyer IIT Bombay Source: WAP Forum 62 WTLS:Wireless Transport Layer SecurityGoals Provide mechanisms for secure transfer of content, for applications needing privacy, identification, message integrity and non-repudiation WTLS is based on the TLS/SSL (Transport Layer Security) protocol optimized for low-bandwidth communication channels provides privacy (encryption) data integrity (MACs) authentication (public-key and symmetric) Employs special adapted mechanisms for wireless usage Long lived secure sessions Optimised handshake procedures Provides simple data reliability for operation over datagram bearers Sridhar Iyer IIT Bombay 63 WTLS: secure session, full handshakeSEC-Create.req (SA, SP, DA, DP, KES, CS, CM) SEC-Create.ind originator SEC-SAP peer SEC-Create.cnf (SNM, KR, SID, KES‘, CS‘, CM‘) SEC-Create.res SEC-Exchange.req SEC-Exchange.ind SEC-Exchange.res (CC) SEC-Commit.req SEC-Exchange.cnf SEC-Commit.ind SEC-Commit.cnf KES: Key Exchange Suite CS: Cipher Suite CM: Compression Mode SNM: Sequence Number Mode KR: Key Refresh Cycle SID: Session Identifier CC: Client Certificate Sridhar Iyer IIT Bombay Source: Schiller 64 WTP: Wireless Transaction ProtocolGoals different transaction services that enable applications to select reliability, efficiency levels low memory requirements, suited to simple devices (< 10kbyte ) efficiency for wireless transmission WTP supports peer-to-peer, client/server and multicast applications efficient for wireless transmission support for different communication scenarios Sridhar Iyer IIT Bombay 65 WTP transactions class 0: unreliable message transferunconfirmed Invoke message with no Result message a datagram that can be sent within the context of an existing Session class 1: reliable message transfer without result message confirmed Invoke message with no Result message used for data push, where no response from the destination is expected class 2: reliable message transfer with exactly one reliable result message confirmed Invoke message with one confirmed Result message a single request produces a single reply Sridhar Iyer IIT Bombay 66 WTP: services and protocolsWTP (Transaction) provides reliable data transfer based on request/reply paradigm no explicit connection setup or tear down optimized setup (data carried in first packet of protocol exchange) seeks to reduce 3-way handshake on initial request supports header compression segmentation /re-assembly retransmission of lost packets selective-retransmission port number addressing (UDP ports numbers) flow control Sridhar Iyer IIT Bombay 67 WTP services message oriented (not stream)supports an Abort function for outstanding requests supports concatenation of PDUs supports two acknowledgement options User acknowledgement acks may be forced from the WTP user (upper layer) Stack acknowledgement: default Sridhar Iyer IIT Bombay 68 WTP Class 0 Transaction initiator TR-SAP responder TR-SAPTR-Invoke.req (SA, SP, DA, DP, A, UD, C=0, H) TR-Invoke.ind (SA, SP, DA, DP, A, UD, C=0, H‘) Invoke PDU A: Acknowledgement Type (WTP/User) C: Class (0,1,2) H: Handle (socket alias) Sridhar Iyer IIT Bombay Source: Schiller 69 WTP Class 1 Transaction, no user ack & user ackTR-Invoke.req (SA, SP, DA, DP, A, UD, C=1, H) Invoke PDU TR-Invoke.ind (SA, SP, DA, DP, A, UD, C=1, H‘) initiator TR-SAP responder Ack PDU TR-Invoke.cnf (H) TR-Invoke.req (SA, SP, DA, DP, A, UD, C=1, H) Invoke PDU TR-Invoke.ind (SA, SP, DA, DP, A, UD, C=1, H‘) initiator TR-SAP responder Ack PDU TR-Invoke.res (H‘) TR-Invoke.cnf (H) Sridhar Iyer IIT Bombay Source: Schiller 70 WTP Class 2 Transaction, no user ack, no hold onTR-Invoke.req (SA, SP, DA, DP, A, UD, C=2, H) Invoke PDU TR-Invoke.ind (SA, SP, DA, DP, A, UD, C=2, H‘) initiator TR-SAP responder Result PDU TR-Result.req (UD*, H‘) TR-Result.ind (UD*, H) Ack PDU TR-Invoke.cnf (H) TR-Result.res TR-Result.cnf (H‘) Sridhar Iyer IIT Bombay Source: Schiller 71 WTP Class 2 Transaction, user ackTR-Invoke.req (SA, SP, DA, DP, A, UD, C=2, H) Invoke PDU TR-Invoke.ind (SA, SP, DA, DP, A, UD, C=2, H‘) initiator TR-SAP responder Result PDU TR-Result.ind (UD*, H) Ack PDU TR-Invoke.res (H‘) TR-Invoke.cnf (H) TR-Result.req (UD*, H‘) TR-Result.res TR-Result.cnf Sridhar Iyer IIT Bombay Source: Schiller 72 WSP - Wireless Session ProtocolGoals HTTP 1.1 functionality Request/reply, content type negotiation, ... support of client/server transactions, push technology key management, authentication, Internet security services WSP Services provides shared state between client and server, optimizes content transfer session management (establish, release, suspend, resume) efficient capability negotiation content encoding Push Sridhar Iyer IIT Bombay 73 WSP overview Header Encoding Capabilities (are defined for):compact binary encoding of headers, content type identifiers and other well-known textual or structured values reduces the data actually sent over the network Capabilities (are defined for): message size, client and server protocol options: Confirmed Push Facility, Push Facility, Session Suspend Facility, Acknowledgement headers maximum outstanding requests extended methods Suspend and Resume server knows when client can accept a push multi-bearer devices dynamic addressing allows the release of underlying bearer resources Sridhar Iyer IIT Bombay 74 WSP/B session establishmentclient S-SAP server S-SAP S-Connect.req (SA, CA, CH, RC) S-Connect.ind (SA, CA, CH, RC) Connect PDU S-Connect.res (SH, NC) S-Connect.cnf (SH, NC) ConnReply PDU CH: Client Header RC: Requested Capabilities SH: Server Header NC: Negotiated Capabilities WTP Class 2 transaction Sridhar Iyer IIT Bombay Source: Schiller 75 WSP/B session suspend/resumeclient S-SAP server S-SAP S-Suspend.req S-Suspend.ind (R) Suspend PDU S-Suspend.ind (R) WTP Class 0 transaction ~ ~ R: Reason for disconnection S-Resume.req (SA, CA) S-Resume.ind (SA, CA) Resume PDU S-Resume.res Reply PDU S-Resume.cnf WTP Class 2 transaction Sridhar Iyer IIT Bombay Source: Schiller 76 WSP/B session terminationclient S-SAP server S-SAP S-Disconnect.req (R) S-Disconnect.ind (R) Disconnect PDU S-Disconnect.ind (R) WTP Class 0 transaction Sridhar Iyer IIT Bombay Source: Schiller 77 confirmed/non-confirmed pushclient S-SAP server S-SAP S-Push.req (PH, PB) S-Push.ind (PH, PB) Push PDU WTP Class 0 transaction PH: Push Header PB: Push Body SPID: Server Push ID CPID: Client Push ID client S-SAP server S-SAP S-ConfirmedPush.req (SPID, PH, PB) S-ConfirmedPush.ind (CPID, PH, PB) ConfPush PDU S-ConfirmedPush.res (CPID) S-ConfirmedPush.cnf (SPID) WTP Class 1 transaction Sridhar Iyer IIT Bombay Source: Schiller 78 WAP Stack Summary WDP WTLS WTP WSPfunctionality similar to UDP in IP networks WTLS functionality similar to SSL/TLS (optimized for wireless) WTP Class 0: analogous to UDP Class 1: analogous to TCP (without connection setup overheads) Class 2: analogous to RPC (optimized for wireless) features of “user acknowledgement”, “hold on” WSP WSP/B: analogous to http 1.1 (add features of suspend/resume) method: analogous to RPC/RMI features of asynchronous invocations, push (confirmed/unconfirmed) Sridhar Iyer IIT Bombay 79 Wireless Application Environment (WAE)Goals device and network independent application environment for low-bandwidth, wireless devices considerations of slow links, limited memory, low computing power, small display, simple user interface (compared to desktops) integrated Internet/WWW programming model high interoperability Sridhar Iyer IIT Bombay 80 WAE components Architecture User Agents WML WMLScript WTAApplication model, Microbrowser, Gateway, Server User Agents WML/WTA/Others content formats: vCard, vCalendar, Wireless Bitmap, WML.. WML XML-Syntax, based on card stacks, variables, ... WMLScript procedural, loops, conditions, ... (similar to JavaScript) WTA telephone services, such as call control, text messages, phone book, ... (accessible from WML/WMLScript) Proxy (Method/Push) Sridhar Iyer IIT Bombay 81 WAE: logical model Origin Servers Gateway Client Method proxy WTAuser agent web server response with content encoded response with content Push proxy WML user agent other content server push content encoded push content encoders & decoders other WAE user agents request encoded request Sridhar Iyer IIT Bombay 82 WAP microbrowser Optimized for wireless devicesMinimal RAM, ROM, Display, CPU and keys Provides consistent service UI across devices Provides Internet compatibility Enables wide array of available content and applications Sridhar Iyer IIT Bombay 83 WML: Wireless Markup LanguageTag-based browsing language: Screen management (text, images) Data input (text, selection lists, etc.) Hyperlinks & navigation support Takes into account limited display, navigation capabilities of devices Content (XML) XSL Processor WML Browsers WML Stylesheet HTTP Browser HTML StyleSheet Sridhar Iyer IIT Bombay 84 WML XML-based language Cards and Decksdescribes only intent of interaction in an abstract manner presentation depends upon device capabilities Cards and Decks document consists of many cards User interactions are split into cards Explicit navigation between cards cards are grouped to decks deck is similar to HTML page, unit of content transmission Events, variables and state mgmt Sridhar Iyer IIT Bombay 85 WML The basic unit is a card. Cards are grouped together into Decks Document ~ Deck (unit of transfer) All decks must contain Document prologue XML & document type declaration 86 WML cards Deck Card Navigation Variables Input Elements 87 Wireless Telephony Application (WTA)Collection of telephony specific extensions designed primarily for network operators Example calling a number (WML) wtai://wp/mc; calling a number (WMLScript) WTAPublic.makeCall(" "); Implementation Extension of basic WAE application model Extensions added to standard WML/WMLScript browser Exposes additional API (WTAI) Sridhar Iyer IIT Bombay 88 WTA features Extension of basic WAE application modelnetwork model for interaction client requests to server event signaling: server can push content to the client event handling table indicating how to react on certain events from the network client may now be able to handle unknown events telephony functions some application on the client may access telephony functions Sridhar Iyer IIT Bombay 89 WTA Interface generic, high-level interface to mobile’s telephony functions setting up calls, reading and writing entries in phonebook WTA API includes Call control Network text messaging Phone book interface Event processing Security model: segregation Separate WTA browser Separate WTA port Sridhar Iyer IIT Bombay 90 WTA Example (WML) Placing an outgoing call with WTAI: WTAI Call 91 WTA Logical Architectureother telephone networks WTA Origin Server WTA & WML server WML Scripts WML decks WTA services Client WAE services WTA user agent mobile network WAP Gateway encoders & decoders network operator trusted domain other WTA servers third party origin servers firewall Sridhar Iyer IIT Bombay Source: Schiller 92 WTA Framework ComponentsSridhar Iyer IIT Bombay Source: Heijden 93 WTA User Agent WTA User AgentWML User agent with extended functionality can access mobile device’s telephony functions through WTAI can store WTA service content persistently in a repository handles events originating in the mobile network Sridhar Iyer IIT Bombay 94 WTA User Agent Context Abstraction of execution spaceHolds current parameters, navigation history, state of user agent Similar to activation record in a process address space Uses connection-mode and connectionless services offered by WSP Specific, secure WDP ports on the WAP gateway Sridhar Iyer IIT Bombay 95 WTA Events Network notifies device of event (such as incoming call)WTA events map to device’s native events WTA services are aware of and able to act on these events example: incoming call indication, call cleared, call connected Sridhar Iyer IIT Bombay 96 WTA Repository local store for content related to WTA services (minimize network traffic) Channels: define the service content format defining a WTA service stored in repository XML document specifying eventid, title, abstract, and resources that implement a service Resources: execution scripts for a service could be WML decks, WML Scripts, WBMP images.. downloaded from WTA server and stored in repository before service is referenced Server can also initiate download of a channel Sridhar Iyer IIT Bombay 97 WTA Channels and ResourcesSridhar Iyer IIT Bombay Source: Heijden 98 WTA Interface (public)for third party WML content providers restricted set of telephony functions available to any WAE User Agent library functions make call: allows application to setup call to a valid tel number send DTMF tones: send DTMF tones through the setup call user notified to grant permission for service execution cannot be triggered by network events example: Yellow pages service with “make call” feature Sridhar Iyer IIT Bombay 99 WTA Interface (network)Network Common WTAI WTA service provider is in operator’s domain all WTAI features are accessible, including the interface to WTA events library functions Voice-call control: setup call, accept, release, send DTMF tones Network text: send text, read text, remove text (SMS) Phonebook: write, read, remove phonebook entry Call logs: last dialed numbers, missed calls, received calls Miscellaneous: terminate WTA user agent, protect context user can give blanket permission to invoke a function example: Voice mail service Sridhar Iyer IIT Bombay 100 WTAI (network) Network Specific WTAIspecific to type of bearer network example: GSM: call reject, call hold, call transfer, join multiparty, send USSD Sridhar Iyer IIT Bombay 101 WTA: event handling Event occurrence Event handlingWTA user agent could be executing and expecting the event WTA user agent could be executing and a different event occurs No service is executing Event handling channel for each event defines the content to be processed upon reception of that event Sridhar Iyer IIT Bombay 102 WTA: event binding association of an event with the corresponding handler (channel) Global binding: channel corresponding to the event is stored in the repository event causes execution of resources defined by the channel example: voice mail service Temporary binding: resources to be executed are defined by the already executing service example: yellow pages lookup and call establishment Sridhar Iyer IIT Bombay 103 Event Handling (no service in execution)Sridhar Iyer IIT Bombay Source: Heijden 104 Event Handling (service already execution)1: Temporary binding exists 2. No temporary binding and context is protected 3: No temporary binding and context is not protected Sridhar Iyer IIT Bombay Source: Heijden 105 WAP Push Services Web push Wireless push WAP pushScheduled pull by client (browser) example: Active Channels no real-time alerting/response example: stock quotes Wireless push accomplished by using the network itself example: SMS limited to simple text, cannot be used as starting point for service example: if SMS contains news, user cannot request specific news item WAP push Network supported push of WML content example: Alerts or service indications Pre-caching of data (channels/resources) Sridhar Iyer IIT Bombay 106 WAP push framework Sridhar Iyer IIT Bombay Source: Heijden 107 Push Access Protocol Based on request/response modelPush initiator is the client Push proxy is the server Initiator uses HTTP POST to send push message to proxy Initiator sends control information as an XML document, and content for mobile (as WML) Proxy sends XML entity in response indicating submission status Initiator can cancel previous push query status of push query status/capabilities of device Sridhar Iyer IIT Bombay 108 Push Proxy Gateway WAP stack (communication with mobile device)TCP/IP stack (communication with Internet push initiator) Proxy layer does control information parsing content transformation session management client capabilities store and forward prioritization address resolution management function Sridhar Iyer IIT Bombay 109 Over the Air (OTA) ProtocolExtends WSP with push-specific functionality Application ID uniquely identifies a particular application in the client (referenced as a URI) Connection-oriented mode client informs proxy of application IDs in a session Connectionless mode well known ports, one for secure and other for non-secure push Session Initiation Application (SIA) unconfirmed push from proxy to client request to create a session for a specific user agent and bearer Sridhar Iyer IIT Bombay 110 WAE Summary WML and WML Script WTA Pushanalogous to HTML and JavaScript (optimized for wireless) microbrowser user agent; compiler in the network WTA WTAI: different access rights for different applications/agents WTA User Agent (analogy with operating systems) Context – Activation Record Channel – Interrupt Handler Resource – Shared routines invoked by interrupt handlers Repository – Library of interrupt handlers feature of dynamically pushing the interrupt handler before the event Push no analogy in Internet Sridhar Iyer IIT Bombay 111 Outline Introduction and Overview Wireless LANs: IEEE 802.11Mobile IP routing TCP over wireless GSM air interface GPRS network architecture Wireless application protocol Mobile agents Mobile ad hoc networks Sridhar Iyer IIT Bombay 112 Call to server procedureStructuring Distributed Applications Call to server procedure Data Client Server results Procedure Client Server Procedure Client Server Data results Remote Evaluation Client Server Data Procedure Code on Demand Sridhar Iyer IIT Bombay 113 Mobile Agents Client Data Server Server Data Data Server Data ServerProcedure + State Client Data Server Procedure + State Procedure + State Server Data Procedure + State Procedure + State Data Server Data Server Mobile Agents Sridhar Iyer IIT Bombay 114 Client/server communication Mobile agent communicationInteraction Model Request Server Client Response Client/server communication Mobile agent Request Server Client Response Mobile agent communication Sridhar Iyer IIT Bombay 115 A generic Mobile Agent FrameworkEvent notification Agent collaboration support Event Manager Execution environment Communication (agent dispatching) Agent life cycle (creation, destruction) User identification Protection (agent, server) Authentication Mobile Agent Agent state Agent checkpoint (fault tolerance) Agent Manager Security Manager Sridhar Iyer IIT Bombay Persistent Manager 116 Example: Student Examination ScenarioPaper Assembler To Distribution Center Cloning = Paper Setter Nodes = Install Agent = Fetch Agent 1 6 4 2 5 Partial Question Paper 3 Comprehensive Question Paper Sridhar Iyer IIT Bombay 117 Dynamic Upgrade Sridhar Iyer IIT Bombay 118 List of Students enrolledExample: Distribution and Testing List of Students enrolled … Single copy of paper Distribution Server Exam Center Distribution Server 1 2 c 5 Each copy returned Separate Copy per user 4 Answered and Returned 3 Each Candidate get a Copy Sridhar Iyer IIT Bombay 119 Example: Evaluation and Resultsc Objective Questions Evaluator Distributor Examiner B Distribution Server Examiner A Examiner C Examiner D Results … Sridhar Iyer IIT Bombay Agents collaborate to produce the final result 120 Mobile Agents Summary Appears to be a useful mechanism for applications on mobile and wireless devices Reduce the network load Help in overcoming latency Execute asynchronously and autonomously Several issues yet to be addressed Heavy frameworks Interoperability Security concerns Sridhar Iyer IIT Bombay 121 Outline Introduction and Overview Wireless LANs: IEEE 802.11Mobile IP routing TCP over wireless GSM air interface GPRS network architecture Wireless application protocol Mobile agents Mobile ad hoc networks Sridhar Iyer IIT Bombay 122 Multi-Hop Wireless May need to traverse multiple links to reach destination Mobility causes route changes Sridhar Iyer IIT Bombay 123 Mobile Ad Hoc Networks (MANET)Host movement frequent Topology change frequent No cellular infrastructure. Multi-hop wireless links. Data must be routed via intermediate nodes. A B Sridhar Iyer IIT Bombay 124 Many Applications Ad hoc networks: Applications:Do not need backbone infrastructure support Are easy to deploy Useful when infrastructure is absent, destroyed or impractical Infrastructure may not be present in a disaster area or war zone Applications: Military environments Emergency operations Civilian environments taxi cab network meeting rooms sports stadiums Sridhar Iyer IIT Bombay 125 MAC in Ad hoc Networks IEEE 802.11 DCF is most popular 802.11 DCF:Easy availability DCF: Uses RTS-CTS to avoid hidden terminal problem Uses ACK to achieve reliability was designed for single-hop wireless Does not do well for multi-hop ad hoc scenarios Reduced throughput Exposed terminal problem Sridhar Iyer IIT Bombay 126 Exposed Terminal ProblemC D A starts sending to B. C senses carrier, finds medium in use and has to wait for A->B to end. D is outside the range of A, therefore waiting is not necessary. A and C are “exposed” terminals Sridhar Iyer IIT Bombay 127 Routing Protocols Proactive protocols Reactive protocolsTraditional distributed shortest-path protocols Maintain routes between every host pair at all times Based on periodic updates; High routing overhead Example: DSDV (destination sequenced distance vector) Reactive protocols Determine route if and when needed Source initiates route discovery Example: DSR (dynamic source routing) Hybrid protocols Adaptive; Combination of proactive and reactive Example : ZRP (zone routing protocol) Sridhar Iyer IIT Bombay 128 Dynamic Source Routing (DSR)Route Discovery Phase: Initiated by source node S that wants to send packet to destination node D Route Request (RREQ) floods through the network Each node appends own identifier when forwarding RREQ Route Reply Phase: D on receiving the first RREQ, sends a Route Reply (RREP) RREP is sent on a route obtained by reversing the route appended to received RREQ RREP includes the route from S to D on which RREQ was received by node D Data Forwarding Phase: S sends data to D by source routing through intermediate nodes Sridhar Iyer IIT Bombay 129 Route Discovery in DSR Y Z S E F B C M L J A G H D K I NRepresents a node that has received RREQ for D from S Sridhar Iyer IIT Bombay 130 Broadcast transmissionRoute Discovery in DSR Y Broadcast transmission Z [S] S E F B C M L J A G H D K I N Represents transmission of RREQ [X,Y] Represents list of identifiers appended to RREQ Sridhar Iyer IIT Bombay 131 Route Discovery in DSR Y Z S [S,E] E F B C M L J A G [S,C] H D K I NNode H receives packet RREQ from two neighbors: potential for collision Sridhar Iyer IIT Bombay 132 Route Discovery in DSR Y Z S E F B [S,E,F] C M L J A G H D K [S,C,G] INode C receives RREQ from G and H, but does not forward it again, because node C has already forwarded RREQ once Sridhar Iyer IIT Bombay 133 Route Discovery in DSR Y Z S E F [S,E,F,J] B C M L J A G H D K I N[S,C,G,K] Nodes J and K both broadcast RREQ to node D Since nodes J and K are hidden from each other, their transmissions may collide Sridhar Iyer IIT Bombay 134 Route Discovery in DSR Y Z S E [S,E,F,J,M] F B C M L J A G H D K I NNode D does not forward RREQ, because node D is the intended target of the route discovery Sridhar Iyer IIT Bombay 135 Route Reply in DSR Y Z S RREP [S,E,F,J,D] E F B C M L J A G H D K I NRepresents RREP control message Sridhar Iyer IIT Bombay 136 Data Delivery in DSR Y Z DATA [S,E,F,J,D] S E F B C M L J A G H D K IPacket header size grows with route length Sridhar Iyer IIT Bombay 137 TCP in MANET Several factors affect TCP in MANET:Wireless transmission errors reducing congestion window in response to errors is unnecessary Multi-hop routes on shared wireless medium Longer connections are at a disadvantage compared to shorter connections, because they have to contend for wireless access at each hop Route failures due to mobility Sridhar Iyer IIT Bombay 138 MANET Summary Routing is the most studied problemInterplay of layers is being researched Large number of simulation based expts Small number of field trials Very few reported deployments Fertile area for imaginative applications Standardizing protocols does not seem to be a very good idea Scope for proprietary solutions with limited interop Sridhar Iyer IIT Bombay 139 References J. Schiller, “Mobile Communications”, Addison Wesley, 2000Wireless LAN, IEEE standards, Mobile IP, RFC 2002, RFC 334, TCP over wireless, RFC 3150, RFC 3155, RFC 3449 A. Mehrotra, “GSM system engineering”, Artech House, 1997 Bettstetter, Vogel and Eberspacher, “GPRS: Architecture, Protocols and Air Interface”, IEEE Communications Survey 1999, 3(3). M.v.d. Heijden, M. Taylor. “Understanding WAP”, Artech House, 2000 Mobile Ad hoc networks, RFC 2501 Others websites: Sridhar Iyer IIT Bombay 140 Thank You Other Tutorials at: www.it.iitb.ac.in/~sri Contact Details:Sridhar Iyer School of Information Technology IIT Bombay, Powai, Mumbai Phone: Sridhar Iyer IIT Bombay
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