CS8601 4 MC NOTES.pdf

CS8601 4 MC NOTES.pdf

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  1 MOBILE COMPUTING Unit IV https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  2 UNIT IV MOBILE TRANSPORTLAYER AND APPLICATION LAYER Mobile TCP – WAP- Architecture – WDP – STLS – WTP- WSP- WAE- WTA Architecture - WML https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Overview of TCP/IP TCP/IPprotocol suite is a collection of a large number of protocols. The four layer of protocols are • Application layer • Transport layer • Internet layer • Network layer • TCP/IP allows any of the standard protocols to be used for network interface 3 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  4 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Architecture of TCP/IP TCP/IPprotocol consists of four layers. 1. Application layer, 2.Transport layer, 3.Internet layer and 4. Network access layer 5 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  1. Application layer: Establish communication with other applications which may be running on separate hosts.  Example http,ftp and telnet. 2. Transport layer:  The purpose of Transport layer is to permit devices on the source and destination hosts to carry on a conversation. Provides reliable end-to-end data transfer services.  Also referred as host-to-host protocol.  The main protocols included at Transport layer are I. TCP (Transmission Control Protocol) and II. UDP (User Datagram Protocol). 3. Internet layer  Internet layer pack data into data packets known as IP datagrams,  which contain source and destination address (logical address or IP address) information that is used to forward the datagrams between hosts and across networks. 6 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  4. Network accesslayer  The Network Access Layer of the TCP/IP model is associated with the Physical Layer (Layer 1) and the Data Link layer (Layer 2) of the OSI model.  The Network Access Layer's function is to move bits (0s and 1s) over the network medium such as coaxial cable, optical fiber, or twisted pair copper wire.  The OSI Physical layer is responsible for converting the frame into a stream of bits suitable for the transmission medium and synchronizes signals for the actual transmission.  On the destination device, the Physical layer reassembles these signals into a data frame.  The OSI Data Link layer is again subdivided into the following two sub layers according to their function:  Media Access Control (MAC) Sublayer :— MAC sublayer provides an interface with the network adapter.  Logical Link Control (LLC) Sublayer :— LLC sublayer is responsible for error-checking functions for frames delivered also responsible for managing links between communicating devices. 7 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Comparison of TCP/IPand OSI network models 8 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Comparison of TCP/IPand OSI network models 9 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Adaptation of TCPWindow  TCP deploys a flow control technique to control congestion in a network.  Traffic congestion occurs when the rate at which data is injected by a host into the network exceeds the rate at which data can be delivered to the network. I. Router buffer overflow. II. Receiver buffer overflow  A flow control technique by TCP helps adapt the rate at sending host end and to prevent overrun at the slow receiver.  The flow control mechanism by TCP called the sliding window protocol. 10 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Improvements of TCPPerformance Traditional networks  Transport protocols typically designed for  Fixed end-systems  Fixed, wired networks  TCP congestion control  Packet loss in fixed networks typically due to (temporary) overload situations  Routers discard packets as soon as the buffers are full  TCP recognizes congestion only indirectly via missing acknowledgements  Retransmissions unwise, they would only contribute to the congestion and make it even worse  Slow-start algorithm as reaction 11 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Classification of Schemes 12 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  TCP Slow Start Sender calculates a congestion window for a receiver  Start with a congestion window size equal to one segment  Exponential increase of the congestion window up to the congestion threshold, then linear increase  Missing acknowledgement causes the reduction of the congestion threshold to one half of the current congestion window  Congestion window starts again with one segment 6/27/2020 13 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Congestion avoidance  Itstarts where slow start stops.  Once congestion window reaches the congestion threshold level, then after that if an acknowledgement is received the window size is increased linearly ic the window size doubling is avoided.  The TCP increases its rate linearly by adding one additional picket to its window at each transmission time. If congestion is detected at any point the TCP is reduces its transmission rate to half the previous value. Makes to right transmission rate.  The is scheme is less aggressive than slow start phase. 6/27/2020 14 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Fast Retransmit/ FastRecovery  TCP sends an acknowledgement only after receiving a packet.  If a sender receives several acknowledgements for the same packet, this is due to a gap in received packets at the receiver.  However, the receiver got all packets up to the gap and is actually receiving packets  Therefore, packet loss is not due to congestion, continue with current congestion window (do not use slow-start) 6/27/2020 15 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  TCP in mobilenetworks TCP assumes congestion if packets are dropped  typically wrong in wireless networks, here we often have packet loss due to transmission errors  furthermore, mobility itself can cause packet loss, if e.g. a mobile node roams from one access point (e.g. foreign agent in Mobile IP) to another while there are still packets in transit to the wrong access point and forwarding is not possible The performance of an unchanged TCP degrades severely  however, TCP cannot be changed fundamentally due to the large base of installation in the fixed network, TCP for mobility has to remain compatible  the basic TCP mechanisms keep the whole Internet together 6/27/2020 16 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Indirect TCP (I-TCP)  Indirect TCP or I-TCP segments the connection  no changes to the TCP protocol for hosts connected to the wired Internet, millions of computers use (variants of) this protocol  optimized TCP protocol for mobile hosts  splitting of the TCP connection at, e.g., the foreign agent into 2 TCP connections, no real end-to-end connection any longer  hosts in the fixed part of the net do not notice the characteristics of the wireless part mobile host access point (foreign agent) wired Internet “wireless” TCP standard TCP 6/27/2020 17 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  I-TCP socket andstate migration mobile host access point2 Internet access point1 socket migration and state transfer 6/27/2020 18 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Indirect TCP II Advantages  no changes in the fixed network necessary, no changes for the hosts (TCP protocol) necessary, all current optimizations to TCP still work  transmission errors on the wireless link do not propagate into the fixed network  simple to control, mobile TCP is used only for one hop between, e.g., a foreign agent and mobile host  therefore, a very fast retransmission of packets is possible, the short delay on the mobile hop is known  Disadvantages  loss of end-to-end semantics, an acknowledgement to a sender does not any longer mean that a receiver really got a packet, foreign agents might crash  higher latency possible due to buffering of data within the foreign agent and forwarding to a new foreign agent 6/27/2020 19 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Snooping TCP (S-TCP) Transparent extension of TCP within the foreign agent  buffering of packets sent to the mobile host  lost packets on the wireless link (both directions!) will be retransmitted immediately by the mobile host or foreign agent, respectively (so called “local” retransmission)  the foreign agent therefore “snoops” the packet flow and recognizes acknowledgements in both directions, it also filters ACKs  changes of TCP only within the foreign agent (+min. MH change) „wired“ Internet buffering of data end-to-end TCP connection local retransmission correspondent host foreign agent mobile host snooping of ACKs 6/27/2020 20 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Snooping TCP II Data transfer to the mobile host  FA buffers data until it receives ACK of the MH, FA detects packet loss via duplicated ACKs or time-out  fast retransmission possible, transparent for the fixed network  Data transfer from the mobile host  FA detects packet loss on the wireless link via sequence numbers, FA answers directly with a NACK to the MH  MH can now retransmit data with only a very short delay  Advantages:  Maintain end-to-end semantics  No change to correspondent node  No major state transfer during handover  Problems  Snooping TCP does not isolate the wireless link well  May need change to MH to handle NACKs  Snooping might be useless depending on encryption schemes 6/27/2020 21 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Mobile TCP(M-TCP)  Specialhandling of lengthy and/or frequent disconnections  M-TCP splits as I-TCP does  unmodified TCP fixed network to supervisory host (SH)  optimized TCP SH to MH  Supervisory host  no caching, no retransmission  monitors all packets, if disconnection detected  set sender window size to 0  sender automatically goes into persistent mode  old or new SH reopen the window  Advantages  maintains semantics, supports disconnection, no buffer forwarding  Disadvantages  loss on wireless link propagated into fixed network  adapted TCP on wireless link 6/27/2020 22 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Mobile TCP(M-TCP) 23 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Fast retransmit/fast recovery Change of foreign agent often results in packet loss  TCP reacts with slow-start although there is no congestion  Forced fast retransmit  as soon as the mobile host has registered with a new foreign agent, the MH sends duplicated acknowledgements on purpose  this forces the fast retransmit mode at the communication partners  additionally, the TCP on the MH is forced to continue sending with the actual window size and not to go into slow-start after registration  Advantage  simple changes result in significant higher performance  Disadvantage  further mix of IP and TCP (to know when there is a new registration), no transparent approach 6/27/2020 24 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Freeze-TCP Mobile hosts canbe disconnected for a longer time  no packet exchange possible, e.g., in a tunnel, disconnection due to overloaded cells or mux. with higher priority traffic  TCP disconnects after time-out completely TCP freezing  MAC layer is often able to detect interruption in advance  MAC can inform TCP layer of upcoming loss of connection  TCP stops sending, but does not assume a congested link  MAC layer signals again if reconnected Advantage  scheme is independent of data and TCP mechanisms (Ack,SN) => works even with IPsec Disadvantage  TCP on mobile host has to be changed, mechanism depends on MAC layer 6/27/2020 25 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Selective retransmission  TCPacknowledgements are often cumulative  ACK n acknowledges correct and in-sequence receipt of packets up to n  if single packets are missing quite often a whole packet sequence beginning at the gap has to be retransmitted (go-back-n), thus wasting bandwidth  Selective retransmission as one solution  RFC2018 allows for acknowledgements of single packets, not only acknowledgements of in- sequence packet streams without gaps  sender can now retransmit only the missing packets  Advantage: much higher efficiency  Disadvantage  more complex software in a receiver, more buffer needed at the receiver 6/27/2020 26 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Transaction oriented TCP TCPphases  connection setup, data transmission, connection release  using 3-way-handshake needs 3 packets for setup and release, respectively  thus, even short messages need a minimum of 7 packets! Transaction oriented TCP  RFC1644, T-TCP, describes a TCP version to avoid this overhead  connection setup, data transfer and connection release can be combined  thus, only 2 or 3 packets are needed Advantage  efficiency Disadvantage  requires changed TCP  mobility no longer transparent 6/27/2020 27 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  28 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  WAP 29 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Layers of WAPProtocol Application Layer Wireless Application Environment (WAE). This layer is of most interest to content developers because it contains among other things, device specifications, and the content development programming languages, WML, and WML Script. Session Layer Wireless Session Protocol (WSP). Unlike HTTP, WSP has been designed by the WAP Forum to provide fast connection suspension and reconnection. 30 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Transaction Layer Wireless TransactionProtocol (WTP). The WTP runs on top of a datagram service, such as User Datagram Protocol (UDP) and is part of the standard suite of TCP/IP protocols used to provide a simplified protocol suitable for low bandwidth wireless stations. Security Layer Wireless Transport Layer Security (WTLS). WTLS incorporates security features that are based upon the established Transport Layer Security (TLS) protocol standard. It includes data integrity checks, privacy, service denial, and authentication services. Transport Layer Wireless Datagram Protocol (WDP). The WDP allows WAP to be bearer-independent by adapting the transport layer of the underlying bearer. The WDP presents a consistent data format to the higher layers of the WAP protocol stack, thereby offering the advantage of bearer independence to application developers. Each of these layers provides a well-defined interface to the layer above it. This means that the internal workings of any layer are transparent or invisible to the layers above it. The layered architecture allows other applications and services to utilise the features provided by the WAP-stack as well. This makes it possible to use the WAP-stack for services and applications that currently are not specified by WAP. The WAP protocol architecture is shown below alongside a typical Internet Protocol stack. 31 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Wireless Application Protocol(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 wapforum.org:  co-founded by Ericsson, Motorola, Nokia, Phone.com  450 members in 2000, comprise of Handset manufacturers, Wireless service providers, ISPs, Software companies in the wireless industry  Goals  deliver Internet services to mobile devices  enable applications to scale across a variety of transport options and device types  independence from wireless network standards  GSM, CDMA IS-95, TDMA IS-136, 3G systems (UMTS, W-CDMA) https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  WAP: Main Features Browser “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 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Internet Model HTML HTTP TLS/SSL TCP/IP https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Web Server Content CGI Scripts etc. WML Decks with WML-Script WAP Gateway WMLEncoder WMLScript Compiler Protocol Adapters Client WML WML-Script WTAI Etc. HTTP WSP/WTP WAP Architecture Source: WAP Forum https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  WAPApplication Server Content Application Logic WML Decks with WML-Script WML Encoder WMLScript Compiler ProtocolAdapters Client WML WML-Script WTAI Etc. WSP/WTP WAP Application Server Source: WAP Forum https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  WAP Architecture Another look KeyComponents • Origin/Web Server • WAP Gateway/Proxy • WAP Protocol Stack • Micro Browser • WML/WML Script • Transcoders • WTA Source: WAP Forum https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  WAP: Network Elements wirelessnetwork fixed network WAP proxy WTA server filter/ WAP proxy web server filter PSTN Internet Binary WML: binary file format for clients Binary WML Binary WML Binary WML HTML HTML HTML WML WML HTML Source: Schiller https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  WAP Specifies Wireless ApplicationEnvironment  WML 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 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  WAP Stack MicroBrowser (WML,WMLScript, WTA, WTAI) Runs on top of WDP Provided lightweight X-oriented service • Unreliable 1-way request • Reliable 1-way/2-way req./response Lightweight SSL Uses WIM/PKI-Cards Datagram service on different bearers Convergence between bearer services Different Wireless Tech. Source: WAP Forum https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  WAP Stack WAE (WirelessApplication 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. 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 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  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 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  WAE Components Architecture  Applicationmodel, 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) https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Origin Servers WAE: LogicalModel web server other content server Gateway Client other WAE user agents WML user agent WTA user agent Push proxy encoded request request encoded response with content response with content push content encoded push content Method proxy encoders & decoders https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  WAP Microbrowser Optimized forwireless devices Minimal RAM, ROM, Display, CPU and keys Provides consistent service UI across devices Provides Internet compatibility Enables wide array of available content and applications https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  WML: Wireless MarkupLanguage Tag-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 XML-based language  describes 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 Content (XML) XSL Processor HTTP Browser HTML StyleSheet WML Browsers WML Stylesheet https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  WML The basic unitis a card. Cards are grouped together into Decks Document ~ Deck (unit of transfer) All decks must contain  Document prologue  XML & document type declaration  <WML> element  Must contain one or more cards <?xml version="1.0"?> <!DOCTYPE WML PUBLIC "-//WAPFORUM//DTD WML 1.0//EN" "http://www.wapforum.org/DTD/wml.xml"> <WML> ... </WML> WML File Structure https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  WML Example Input Elements Deck Card Navigation Variables <WML> <CARD> <DO TYPE=“ACCEPT”> <GOURL=“#eCard”/> </DO Welcome! </CARD> <CARD NAME=“eCard”> <DO TYPE=“ACCEPT”> <GO URL=“/submit?N=$(N)&S=$(S)”/> </DO> Enter name: <INPUT KEY=“N”/> Choose speed: <SELECT KEY=“S”> <OPTION VALUE=“0”>Fast</OPTION> <OPTION VALUE=“1”>Slow</OPTION> <SELECT> </CARD> </WML> https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Wireless Telephony Application (WTA) Collectionof telephony specific extensions  designed primarily for network operators Example  calling a number (WML) wtai://wp/mc;07216086415  calling a number (WMLScript) WTAPublic.makeCall("07216086415"); Implementation  Extension of basic WAE application model  Extensions added to standard WML/WMLScript browser  Exposes additional API (WTAI) https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  WTA Features Extension ofbasic WAE application model  network 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 WTAI includes:  Call control  Network text messaging  Phone book interface  Event processing Security model: segregation  Separate WTA browser  Separate WTA port https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Placing an outgoingcall with WTAI: Input Element WTAI Call <WML> <CARD> <DO TYPE=“ACCEPT”> <GO URL=“wtai:cc/mc;$(N)”/> </DO> Enter phone number: <INPUT TYPE=“TEXT” KEY=“N”/> </CARD> </WML> WTA Example (WML) Source: WAP Forum https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  Placing an outgoingcall with WTAI: WTAI Call function checkNumber(N) { if (Lang.isInt(N)) WTAI.makeCall(N); else Dialog.alert(“Bad phone number”); } WTA Example (WMLScript) Source: WAP Forum https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
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  WTA Logical Architecture otherWTA servers Client WAE services WTA user agent WAP Gateway encoders & decoders other telephone networks WTA Origin Server WTA & WML server WML Scripts WML decks WTA services mobile network firewall third party origin servers network operator trusted domain Source: Schiller https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 54.
  WTA Framework Components Source:Heijden https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 55.
  WTA User Agent WTAUser Agent  WML 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 WTA User Agent Context  Abstraction of execution space  Holds 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 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 56.
  WTA Events andRepository 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 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 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 57.
  WTA Channels andResources Source: Heijden https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 58.
  WAP: Protocol Stack Source:Schiller Bearers (GSM, CDPD, ...) Security Layer (WTLS) Session Layer (WSP) Application Layer (WAE) Transport Layer (WDP) TCP/IP, UDP/IP, media SSL/TLS HTML, Java HTTP Internet WAP WAE comprises WML (Wireless Markup Language), WML Script, WTAI etc. Transaction Layer (WTP) additional services and applications WCMP A-SAP S-SAP TR-SAP SEC-SAP T-SAP https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 59.
  WDP: Wireless DatagramProtocol Goals  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 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 60.
  WDP: Service Primitives T-SAPT-SAP T-DUnitdata.req (DA, DP, SA, SP, UD) T-DUnitdata.ind (SA, SP, UD) T-DUnitdata.req (DA, DP, 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 Source: Schiller https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 61.
  WAP Over GSMCircuit-Switched RAS - Remote Access Server IWF - InterWorking Function WSP WAE Subnetwork IP WSP WAE Apps on Other Servers WAP Proxy/Server CSD-RF PPP IP Mobile IWF PSTN Circuit CSD-RF ISP/RAS Subnetwork PSTN Circuit PPP IP WTP UDP WTP UDP Service, Protocol, and Bearer Example Source: WAP Forum https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 62.
  WAP Over GSMShort Message Service SMS WDP WTP WSP WAE SMS Subnetwork WDP WDP Tunnel Protocol Subnetwork WDP Tunnel Protocol WTP WSP WAE Apps on other servers SMSC WAP Proxy/Server Mobile under development Service, Protocol, and Bearer Example Source: WAP Forum https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 63.
  WTLS:Wireless Transport Layer Security Goals Provide mechanisms for secure transfer of content, for applications needing privacy, identification, message integrity and non-repudiation  Provide support for protection against denial-of-service attacks 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 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 64.
  Record Protocol Handshake Protocol Alert ProtocolApplication Protocol Change Cipher Spec Protocol Transaction Protocol (WTP) Datagram Protocol (WDP/UDP) Bearer networks WTLS Record protocol WTLS Internal Architecture Source: WAP Forum https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 65.
  WTLS: Secure session,Full handshake SEC-Create.req (SA, SP, DA, DP, KES, CS, CM) SEC-Create.ind (SA, SP, DA, DP, KES, CS, CM) originator SEC-SAP peer SEC-SAP SEC-Create.cnf (SNM, KR, SID, KES‘, CS‘, CM‘) SEC-Create.res (SNM, KR, SID, KES‘, CS‘, CM‘) SEC-Exchange.req SEC-Exchange.ind SEC-Exchange.res (CC) SEC-Commit.req SEC-Exchange.cnf (CC) SEC-Commit.ind SEC-Commit.cnf Source: Schiller KES: Key Exchange Suite CS: Cipher Suite CM: Compression Mode SNM: Sequence Number Mode KR: Key Refresh Cycle SID: Session Identifier CC: Client Certificate https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 66.
  WTLS: Transferring Datagrams SEC-Unitdata.req (SA,SP, DA, DP, UD) SEC-Unitdata.ind (SA, SP, DA, DP, UD) sender SEC-SAP receiver SEC-SAP Source: Schiller https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 67.
  WTP: Wireless Transaction Protocol Goals 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  class 0: unreliable message transfer  unconfirmed 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 https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 68.
  WTP Services andProtocols WTP (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  message oriented (not stream)  supports an Abort function for outstanding requests  supports concatenation of PDUs  supports User acknowledgement or Stack acknowledgement option  acks may be forced from the WTP user (upper layer)  default is stack ack https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 69.
  WTP Class 0Transaction TR-Invoke.req (SA, SP, DA, DP, A, UD, C=0, H) TR-Invoke.ind (SA, SP, DA, DP, A, UD, C=0, H‘) initiator TR-SAP responder TR-SAP Source: Schiller A: Acknowledgement Type (WTP/User) C: Class (0,1,2) H: Handle (socket alias) https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 70.
  WTP Class 1Transaction, no user ack & user ack TR-Invoke.req (SA, SP, DA, DP, A, UD, C=1, H) TR-Invoke.ind (SA, SP, DA, DP, A, UD, C=1, H‘) initiator TR-SAP responder TR-SAP TR-Invoke.res (H‘) TR-Invoke.cnf (H) TR-Invoke.req (SA, SP, DA, DP, A, UD, C=1, H) TR-Invoke.ind (SA, SP, DA, DP, A, UD, C=1, H‘) initiator TR-SAP responder TR-SAP TR-Invoke.cnf (H) Source: Schiller https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 71.
  WTP Class 2Transaction, no user ack, no hold on TR-Invoke.req (SA, SP, DA, DP, A, UD, C=2, H) TR-Invoke.ind (SA, SP, DA, DP, A, UD, C=2, H‘) initiator TR-SAP responder TR-SAP TR-Result.req (UD*, H‘) TR-Result.ind (UD*, H) TR-Invoke.cnf (H) TR-Result.res (H) TR-Result.cnf (H‘) Source: Schiller https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 72.
  WTP Class 2Transaction, user ack TR-Invoke.req (SA, SP, DA, DP, A, UD, C=2, H) TR-Invoke.ind (SA, SP, DA, DP, A, UD, C=2, H‘) initiator TR-SAP responder TR-SAP TR-Result.ind (UD*, H) TR-Invoke.res (H‘) TR-Invoke.cnf (H) TR-Result.req (UD*, H‘) TR-Result.res (H) TR-Result.cnf (H‘) Source: Schiller https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 73.
  WTP Class 2Transaction, hold on, no user ack TR-Invoke.req (SA, SP, DA, DP, A, UD, C=2, H) TR-Invoke.ind (SA, SP, DA, DP, A, UD, C=2, H‘) initiator TR-SAP responder TR-SAP TR-Result.req (UD*, H‘) TR-Result.ind (UD*, H) TR-Invoke.cnf (H) TR-Result.res (H) TR-Result.cnf (H‘) Source: Schiller https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 74.
  WSP - WirelessSession Protocol Goals  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 WSP/B (Browsing)  HTTP/1.1 functionality - but binary encoded  exchange of session headers  push and pull data transfer  asynchronous requests https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 75.
  WSP Overview Header Encoding 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  header code pages Suspend and Resume  server knows when client can accept a push  multi-bearer devices  dynamic addressing  allows the release of underlying bearer resources https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 76.
  WSP Sessions Session Contextand Push  push can take advantage of session headers  server knows when client can accept a push Connection-mode  long-lived communication, benefits of the session state, reliability Connectionless-mode  stateless applications, no session creation overhead, no reliability overhead https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 77.
  WSP/B session establishment S-Connect.req (SA,CA, CH, RC) S-Connect.ind (SA, CA, CH, RC) client S-SAP server S-SAP S-Connect.res (SH, NC) S-Connect.cnf (SH, NC) WTP Class 2 transaction Source: Schiller CH: Client Header RC: Requested Capabilities SH: Server Header NC: Negotiated Capabilities https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 78.
  WSP/B session suspend/resume S-Suspend.reqS-Suspend.ind (R) client S-SAP server S-SAP S-Resume.res WTP Class 2 transaction S-Suspend.ind (R) ~ ~ S-Resume.req (SA, CA) S-Resume.ind (SA, CA) S-Resume.cnf WTP Class 0 transaction Source: Schiller R: Reason for disconnection https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 79.
  WSP/B session termination S-Disconnect.ind (R) client S-SAP server S-SAP S-Disconnect.ind (R)WTP Class 0 transaction S-Disconnect.req (R) Source: Schiller https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 80.
  WSP/B method invoke S-MethodInvoke.req (CTID,M, RU) S-MethodInvoke.ind (STID, M, RU) client S-SAP server S-SAP S-MethodInvoke.res (STID) S-MethodInvoke.cnf (CTID) WTP Class 2 transaction S-MethodResult.req (STID, S, RH, RB) S-MethodResult.ind (CTID, S, RH, RB) S-MethodResult.res (CTID) S-MethodResult.cnf (STID) CTID: Client Transaction ID M: Method Invoked RU: Request URI STID: Server Transaction ID S: Response Status RH: Response Header RB: Response Body Source: Schiller https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 81.
  WSP/B over WTP- method invocation S-MethodInvoke.req S-MethodInvoke.ind client S-SAP server S-SAP S-MethodInvoke.res S-MethodInvoke.cnf S-MethodResult.req S-MethodResult.ind S-MethodResult.res S-MethodResult.cnf TR-Invoke.req initiator TR-SAP TR-Result.ind TR-Invoke.cnf TR-Result.res TR-Invoke.ind responder TR-SAP TR-Invoke.res TR-Result.req TR-Result.cnf Source: Schiller https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 82.
  WSP/B over WTP- asynchronous, unordered requests S-MethodInvoke_1.req S-MethodInvoke_1.ind client S-SAP server S-SAP S-MethodInvoke_2.req S-MethodInvoke_3.req S-MethodResult_1.ind S-MethodInvoke_4.req S-MethodResult_3.ind S-MethodResult_4.ind S-MethodResult_2.ind S-MethodInvoke_3.ind S-MethodInvoke_2.ind S-MethodResult_1.req S-MethodResult_2.req S-MethodResult_3.req S-MethodResult_4.req S-MethodInvoke_4.ind Source: Schiller https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 83.
  WSP/B - confirmed/non-confirmed pushS-Push.req (PH, PB) client S-SAP server S-SAP WTP Class 1 transaction S-Push.ind (PH, PB) S-ConfirmedPush.res (CPID) S-ConfirmedPush.ind (CPID, PH, PB) WTP Class 0 transaction S-ConfirmedPush.req (SPID, PH, PB) client S-SAP server S-SAP S-ConfirmedPush.cnf (SPID) Source: Schiller PH: Push Header PB: Push Body SPID: Server Push ID CPID: Client Push ID https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com
• 84.
  WSP/B over WDP S-Unit-MethodInvoke.req (SA,CA, TID, M, RU) client S-SAP server S-SAP S-Unit-MethodResult.ind (CA, SA, TID, S, RH, RB) S-Unit-Push.ind (CA, SA, PID, PH, PB) S-Unit-MethodInvoke.ind (SA, CA, TID, M, RU) S-Unit-MethodResult.req (CA, SA, TID, S, RH, RB) S-Unit-Push.req (CA, SA, PID, PH, PB) WDP Unitdata service Source: Schiller https://play.google.com/store/apps/details?id=com.sss.edubuzz360 www.edubuzz360.com