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TABLE OF CONTENTS.doc

  1. 1. Bilkent University Department of Computer Engineering - CS 491 - Senior Design Project 1 Analysis Report Group Members: Emrah Bayraktaroğlu 20200944 Berk Berker 20201826 S. Tuncer Erdoğan 20200854 Mustafa Ömer Kılavuz 20202180 Erkan Okuyan 20201633 Supervisor: Assistant Professor Dr. İbrahim Körpeoğlu October 22, 2005 This report is submitted to the Department of Computer Engineering of Bilkent University in partial fulfillment of the requirements of the Senior Projects course CS492.
  2. 2. Bilkent University – Department of Computer Engineering TABLE OF CONTENTS TABLE OF CONTENTS.....................................................................................................2 1. Introduction......................................................................................................................3 2. Current system.................................................................................................................4 2.1 IEEE 802.11...............................................................................................................4 2.1.1 802.11b................................................................................................................4 2.1.2 802.11a................................................................................................................5 2.1.3 802.11g................................................................................................................5 2.1.4 802.11n................................................................................................................6 2.2 Streaming Media........................................................................................................6 2.2.1 History.................................................................................................................6 2.2.2 Streaming bandwidth and storage.......................................................................7 2.2.3 Protocol Issues....................................................................................................8 2.2.4 Advantages of Streaming....................................................................................8 2.2.5 Real-time Streaming Versus Progressive Download..........................................9 3. Proposed system.............................................................................................................10 3.1 Overview..................................................................................................................10 3.1.1 Project Definition..............................................................................................10 3.2 Functional Requirements.........................................................................................10 3.3 Nonfunctional Requirements...................................................................................11 3.3.1 Response Time..................................................................................................11 3.3.2 Throughput........................................................................................................11 3.3.3 Resource Usage.................................................................................................11 3.3.4 Reliability..........................................................................................................11 3.3.5 Availability.......................................................................................................11 3.3.6 Recovery from Failure......................................................................................12 3.3.7 Platform.............................................................................................................12 3.4 Pseudo requirements................................................................................................12 3.5 System models.........................................................................................................12 3.5.1 Scenarios...........................................................................................................12 3.5.2 Use case model.................................................................................................13 3.5.3 Dynamic models...............................................................................................15 3.5.4 User interface - navigational paths and screen mock-ups.................................18 4. Glossary.........................................................................................................................19 5. References......................................................................................................................20 2
  3. 3. Bilkent University – Department of Computer Engineering 1. Introduction Wireless networking is the key feature of the technologic devices of the current century. The high-speed evolution and the expansion of the Internet and the development of smaller devices with highly sophisticated characteristics bring the end-user the chance to demand the advanced techniques from technology vendors. As a result of this wide demand for new technologies, technology vendors are pushing the limits further, improving hardware technologies and forcing the hardware to be used at full capacity by developing new aspects of software. Wireless LAN is expected to continue to be an important form of connection in many business areas. The market is expected to grow as the benefits of WLAN are recognized. Frost and Sullivan estimate the WLAN market to have been 0.3 billion US dollars in 1998 and 1.6 billion dollars in 2005. So far WLANs have been installed in universities, airports, and other major public places. Decreasing costs of WLAN equipment has also brought it to many homes. WLAN components are now cheap enough to be used in the home, with many being set-up so that one PC (a parent's PC, for example) can be used to share an internet connection with the whole family (whilst retaining access control at the parents' PC). (Wikipedia, WLAN) Multimedia streaming is one of the most important branches of this technological revolution. End-users demand to watch newest movie trailers, music videos, listen to new tracks, and even watch live TV shows&series, movies, news. On the other hand big vendors of the field want to sell their products, movies, mp3’s etc, even from wireless networks. Former technologies like infrared connection and bluetooth restricts the users to a low bandwidth connection without the ability to stream multimedia fluently. IEEE 802.11g standard, a newly developed technology announced in June 2003 provides a bandwidth up to 54 Mbit/s and provides the necessary bandwidth for multimedia streaming applications. 3
  4. 4. Bilkent University – Department of Computer Engineering 2. Current system 2.1 IEEE 802.11 IEEE 802.11 or Wi-Fi denotes a set of Wireless LAN standards developed by working group 11 of the IEEE LAN/MAN Standards Committee (IEEE 802). The term is also used to refer to the original 802.11, which is now sometimes called "802.11 legacy." The 802.11 family currently includes six over-the-air modulation techniques that all use the same protocol, the most popular (and prolific) techniques are those defined by the a, b, and g amendments to the original standard; security was originally included, and was later enhanced via the 802.11i amendment. Other standards in the family (c–f, h–j, n) are service enhancement and extensions, or corrections to previous specifications. 802.11b was the first widely accepted wireless networking standard, followed (somewhat counterintuitively) by 802.11a and 802.11g. 802.11b and 802.11g standards use the unlicensed 2.4 gigahertz (GHz) band. The 802.11a standard uses the 5 GHz band. Operating in an unregulated frequency band, 802.11b and 802.11g equipment can incur interference from microwave ovens, cordless phones, and other appliances using the same 2.4 GHz band. 2.1.1 802.11b The 802.11b amendment to the original standard was ratified in 1999. 802.11b has a maximum raw data rate of 11 Mbit/s and uses the same CSMA/CA media access method defined in the original standard. Due to the CSMA/CA protocol overhead, in practice the maximum 802.11b throughput that an application can achieve is about 5.9 Mbit/s over TCP and 7.1 Mbit/s over UDP. 802.11b is usually used in a point-to-multipoint configuration, wherein an access point communicates via an omni-directional antenna with one or more clients that are located in a coverage area around the access point. With high-gain external antennas, the protocol can also be used in fixed point-to-point arrangements, typically at ranges up to eight kilometers (km) although some report success at ranges up to 80–120 km where line of sight can be established. This is usually done in place of costly leased lines or very cumbersome microwave communications equipment. 802.11b cards can operate at 11 Mbit/s, but will scale back to 5.5, then 2, then 1 Mbit/s (a.k.a Adaptive Rate Selection), if signal quality becomes an issue. Since the lower data rates use less complex and more redundant methods of encoding the data, they are less susceptible to corruption due to interference and signal attenuation. Extensions have been made to the 802.11b protocol (e.g., channel bonding and burst transmission techniques) in order to increase speed to 22, 33, and 44 Mbit/s, but the extensions are proprietary and have not been endorsed by the IEEE. Many companies call enhanced versions "802.11b+". These extensions have been largely obviated by the development of 802.11g, which has data rates up to 54 Mbit/s and is backwards-compatible with 802.11b. 4
  5. 5. Bilkent University – Department of Computer Engineering 2.1.2 802.11a The 802.11a amendment to the original standard was ratified in 1999. The 802.11a standard uses the same core protocol as the original standard, operates in 5 GHz band, and uses a 52-subcarrier orthogonal frequency-division multiplexing (OFDM) with a maximum raw data rate of 54 Mbit/s, which yields realistic net achievable throughput in the mid-20 Mbit/s. The data rate is reduced to 48, 36, 24, 18, 12, 9 then 6 Mbit/s if required. 802.11a has 12 non-overlapping channels, 8 dedicated to indoor and 4 to point to point. It is not interoperable with 802.11b, except if using equipment that implements both standards. Since the 2.4 GHz band is heavily used, using the 5 GHz band gives 802.11a the advantage of less interference. However, this high carrier frequency also brings disadvantages. It restricts the use of 802.11a to almost line of sight, necessitating the use of more access points; it also means that 802.11a cannot penetrate as far as 802.11b since it is absorbed more readily, other things (such as power) being equal. 802.11a products started shipping in 2001, lagging 802.11b products due to the slow availability of the 5 GHz components needed to implement products. 802.11a was not widely adopted overall because 802.11b was already widely adopted, because of 802.11a's disadvantages, because of poor initial product implementations, making its range even shorter, and because of regulations. Manufacturers of 802.11a equipment responded to the lack of market success by improving the implementations (current- generation 802.11a technology has range characteristics much closer to those of 802.11b), and by making technology that can use more than one 802.11 standard. There are dual-band, or dual-mode or tri-mode cards that can automatically handle 802.11a and b, or a, b and g, as available. Similarly, there are mobile adapters and access points which can support all these standards simultaneously 2.1.3 802.11g In June 2003, a third modulation standard was ratified: 802.11g. This flavor works in the 2.4 GHz band (like 802.11b) but operates at a maximum raw data rate of 54 Mbit/s, or about 24.7 Mbit/s net throughput like 802.11a. It is fully backwards compatible with b and uses the same frequencies. Details of making b and g work well together occupied much of the lingering technical process. In older networks, however, the presence of an 802.11b participant significantly reduces the speed of an 802.11g network. The 802.11g standard swept the consumer world of early adopters starting in January 2003, well before ratification. The corporate users held back and Cisco and other big equipment makers waited until ratification. By summer 2003, announcements were flourishing. Most of the dual-band 802.11a/b products became dual-band/tri-mode, supporting a, b, and g in a single mobile adaptor card or access point. While 802.11g held the promise of higher throughput, actual results were mitigated by a number of factors: conflict with 802.11b-only devices, exposure to the same interference sources as 802.11b, limited channelization (only 3 fully non- overlapping channels like 802.11b) and the fact that the higher data rates of 802.11g are often more susceptible to interference than 802.11b, causing the 802.11g device to reduce the data rate to effectively the same rates used by 802.11b. The move to dual-mode/tri- 5
  6. 6. Bilkent University – Department of Computer Engineering mode products also carries with it economies of scale (e.g. single chip manufacturing). For the consumer, dual-band/tri-mode products ensure the best possible throughput in any given environment. The first major manufacturer to use 802.11g was Apple, under the trademark AirPort Extreme. Cisco joined the game by buying up Linksys, an early adopter, and also offers its own wireless mobile adaptors under the name Aironet. 2.1.4 802.11n In January 2004 IEEE announced that it had formed a new 802.11 Task Group (TGn) to develop a new amendment to the 802.11 standard for local-area wireless networks. The real data throughput is estimated to reach a theoretical 540 Mbit/s (which may require an even higher raw data rate at the physical layer), and should be up to 10 times faster than 802.11a or 802.11g, and near 40 times faster than 802.11b. It is projected that 802.11n will also offer a better operating distance than current networks. There are two competing proposals of the 802.11n standard, expected to be ratified: WWiSE (World-Wide Spectrum Efficiency), backed by companies including Broadcom, and TGnSync backed by Intel and Philips. Previous competitors TGnSync, WWiSE and a third group, MITMOT said late July 2005 they will merge their respective proposals as a draft which will be sent to the IEEE in September and a final version will be submitted in November. The standardization process is expected to be completed by the second half of 2006. 802.11n builds upon previous 802.11 standards by adding MIMO (multiple-input multiple-output) and orthogonal frequency-division multiplexing (OFDM). MIMO uses multiple transmitter and receiver antennas to allow for increased data throughput through spatial multiplexing and increased range by exploiting the spatial diversity, perhaps through coding schemes like Alamouti coding. 2.2 Streaming Media Streaming media is media that is consumed (read, heard, viewed) while it is being delivered. Although it is generally used in the context of certain content types ("streaming audio", "streaming video", etc), streaming is more a property of the delivery systems employed to distribute that content. The distinction is usually applied to media that are distributed over computer networks; most other delivery systems are either inherently streaming (radio, television) or inherently non-streaming (books, video cassettes, audio CDs). 2.2.1 History Attempts to display media on computers date back to the earliest days of computing, in the mid-20th century. However, little progress was made for several decades, due primarily to the high cost and limited capabilities of computer hardware. Academic experiments in the 1970s proved out the basic concepts and feasibility of streaming media on computers. During the late 1980s, consumer-grade computers became powerful enough to display various media. The primary technical issues with streaming were: 6
  7. 7. Bilkent University – Department of Computer Engineering • having enough CPU power and bus bandwidth to support the required data rates • creating low-latency interrupt paths in the OS to prevent buffer underrun However, computer networks were still limited, and media were usually delivered over non-streaming channels. In the 1990s, CD-ROMs became the most prevalent method of media distribution to computers. The late 1990s saw: • greater network bandwidth, especially in the last mile • increased access to networks, especially the Internet • use of standard protocols and formats, such as TCP/IP, HTTP, and HTML • commercialization of the Internet These advances in computer networking combined with powerful home computers and modern operating systems to make streaming media practical and affordable for ordinary consumers. In general, multimedia content is large, such that media storage and transmission costs are still significant; to offset this somewhat, media are generally compressed for both storage and streaming. A media stream can be on demand or live. On demand streams are stored on a server for a long period of time, and are available to be transmitted at a user's request. Live streams are only available at one particular time, as in a video stream of a live sporting event. 2.2.2 Streaming bandwidth and storage Streaming media storage size (in the common file system measurements mebibytes, gibibytes, tebibytes, and so on) is calculated from streaming bandwidth and length of the media with the following formula (for a single user and file): storage size (in mebibytes) = length (in seconds) · bit rate (in kbit/s) / 8,388.608 (since 1 mebibyte = 8 * 1,048,576 bits = 8,388.608 kilobits) Real world example: One hour of video encoded at 300 kbit/s (this is a typical broadband video for 2005 and its usually encoded in a 320×240 pixels window size) will be: (3,600 s · 300 kbit/s) / 8,388.608 = 128.7 MiB of storage if the file is stored on a server for on-demand streaming. If this stream is viewed by 1,000 people, you would need 300 kbit/s · 1,000 = 300,000 kbit/s = 300 Mbit/s of bandwidth This is equivalent to 128.7 MiB per hour. 7
  8. 8. Bilkent University – Department of Computer Engineering 2.2.3 Protocol Issues Datagram protocols, such as the User Datagram Protocol (UDP), send the media stream as a series of small packets, called datagrams. This is simple and efficient; however, packets are liable to be lost or corrupted in transit. Depending on the protocol and the extent of the loss, the client may be able to recover the data with error correction techniques, may interpolate over the missing data, or may suffer a dropout. The Real-time Transport Protocol (RTP), the Real Time Streaming Protocol (RTSP) and the Real Time Control Protocol (RTCP) were specifically designed to stream media over the network. They are all built on top of UDP. Reliable protocols, such as the Transmission Control Protocol (TCP), guarantee correct delivery of each bit in the media stream. However, they accomplish this with a system of timeouts and retries, which makes them more complex to implement. It also means that when there is data loss on the network, the media stream stalls while the protocol handlers detect the loss and retransmit the missing data. Clients can minimize the effect of this by buffering data for display. Another issue is that firewalls are more likely to block UDP-based protocols than TCP-based protocols. Unicast protocols send a separate copy of the media stream from the server to each client. This is simple, but can lead to massive duplication of data on the network. Multicast protocols undertake to send only one copy of the media stream over any given network connection, i.e. along the path between any two network routers. This is a more efficient use of network capacity, but it is much more complex to implement. Furthermore, multicast protocols must be implemented in the network routers, as well as the servers. As of 2005, most routers on the Internet do not support multicast protocols, and many firewalls block them. Multicast is most practical for organizations that run their own networks, such as universities and corporations. Since they buy their own routers and run their own network links, they can decide if the cost and effort of supporting a multicast protocol is justified by the resulting bandwidth savings. Peer-to-peer (P2P) protocols arrange for media to be sent from clients that already have them to clients that do not. This prevents the server and its network connections from becoming a bottleneck. However, it raises technical, performance, quality, business, and legal issues. 2.2.4 Advantages of Streaming • Instant play • Deliver long form media • Deliver live broadcasts • Multicasts (one stream to many viewers) • Eliminates the need to download files to the hard drive • Distribution control • Can stream individual tracks into a movie from any streaming server anywhere 8
  9. 9. Bilkent University – Department of Computer Engineering 2.2.5 Real-time Streaming Versus Progressive Download Progressive download allows users to watch or listen to media as it is being downloaded from a standard web server (such as Apache, Microsoft IIS) to their hard drive. This method works best for short-form media where file size is limited. Progressive download ensures high-quality playback regardless of users' Internet connection speed, although users with slower connections will wait longer before media starts to play. Real-time streaming using QuickTime, RealSystem, Windows Media, Helix, ShoutCast Streaming Servers delivers media in real time over the Internet, from modem to broadband rates. With the open standard Real-Time Transport Protocol/Real-Time Streaming Protocol (RTP/RTSP), no file is ever downloaded to a viewer's hard drive. Media is played, but not stored, by the client software as it is delivered. Real-time streaming is often preferable to progressive download for webcasts of live events, delivery of long-form video and 24/7 Internet radio and TV channels. 9
  10. 10. Bilkent University – Department of Computer Engineering 3. Proposed system 3.1 Overview 3.1.1 Project Definition The wireless multimedia streaming over the wireless networks project is constructed to satisfy the following goals: 1) First of all, designing a system to provide multimedia streaming from a non-wireless local server to a laptop supporting wireless connectivity over an access point. 2) Expanding this wireless streaming process to small wireless devices such as PDAs by limiting the third party library usage. 3) Providing a connection layer between two wireless devices, so enabling the ability to stream directly between two wireless devices, PDAs, laptops, etc. 4) Future Work: Building up an ad-hoc network to expand the access area of the streaming network. The first part of the project is the fundamental part of the remaining work. Building up the connection between two devices over the wireless network layer is the first key point. The existing problems of wireless connection process and new techniques to provide better connection mechanism will be discovered. On the other hand, multimedia streaming is the second key point to be explored. After building up the first part, the second part of the project comes into existence. Deploying project into small wireless devices segment, removing the unsupported features, libraries from the project and altering them with other libraries and code segments will be the challenge of the second part. Third part is the expansion of the wireless connectivity level code. Direct connection will be established between two wireless devices at this phase and even small devices such as PDAs will gain the ability to act as a server for the other wireless devices. Fourth part is thought as an extra work for the project, and if the necessary time is left for this part, second expansion to the wireless connectivity level code will be applied. By the help of intelligent routing algorithms, two wireless devices which are out of their connection ranges will be connected over the other wireless devices. Rapidly chancing, dynamic network topology must be explorer instantly and the connection between the devices must be supplied in a very healthy, effective and responsive manner. This is the last challenge of the project. 3.2 Functional Requirements Firstly, the main area of our system is usually away from user interaction, and is mostly in the background on the network layer. Since our system’s major objective is providing a successful multimedia streaming over a network with restricted resources, the functional goal will be supplying a clean user interaction on the user end of the system. The functional requirements will be: 10
  11. 11. Bilkent University – Department of Computer Engineering • The main user interface will be a common multimedia player interface. • The user will be able to connect a wireless device using its IP, if the device supports. (possible laptops and PCs in the system) • The user will be able to connect a wireless device by searching the accessible area around his/her device. Also the user will be able to search a multimedia file within the wireless network. • Once the user connects a device and selects a file, he/she will be able to stream it. • The status of the streaming will be shown on the screen. • The user will be authoritative on connections to his/her device. He/she will be able to allow or stop streaming from his/her device. • The user will be able to allow or forbid streaming, refuse to be a server. • The user will be able to share his/her multimedia files to be streamed. 3.3 Nonfunctional Requirements 3.3.1 Response Time While user starts streaming he/she should not wait much longer for connecting or buffering. These delays should be shortened with proper algorithms or techniques. Also, the response time of the functionalities of the controls should not annoy the user. 3.3.2 Throughput The sender should estimate the capacity correctly. According to estimation it should serve efficiently and should share the capacity fairly and smartly to the receivers. On the other hand, the receivers should arrange the play/buffer balance well to show a smooth performance. 3.3.3 Resource Usage The applications will need memory, CPU and connection bandwidth. Memory usage will be determined according to the buffer size. CPU usage will be determined by the media streaming algorithms. The connection bandwidth usage will be determined by the capacity itself and the desired performance and quality of the media. The applications should use them all efficiently. 3.3.4 Reliability Because of the main purpose is basically streaming media over wireless network, reliability is not so important. On the other hand, for a smooth, in quality and successful streaming the reliability of the algorithms, connection and performing should be considered. 3.3.5 Availability The server should run continuously and flawless during when idle or while streaming. Some technical problems like changes in signal strength may cause problems. So, the tools, algorithms and techniques should be chosen appropriate to the environment to minimize the occurrences of crashes and some exceptions should be handled to behave according to the instant capacity. 11
  12. 12. Bilkent University – Department of Computer Engineering 3.3.6 Recovery from Failure The system should recover from failure. Streaming is a continuous process, so, recovery should be as fast as it can be. To recover some fatal errors may not be possible, but small problems such as lost or damaged packets can be recovered in time. In the case of unsuccessful recovery the continuity of the process should not be interrupted. 3.3.7 Platform The system should work on desktop PCs, laptops and Palms as domain. So, it should be able to adapt for common operating systems that work on these machines. The domain may be extended with more platforms such as cell phones or any other device that has a sufficient display and wireless network connection. And it may also be available for other operating systems that work on these devices especially on PCs. 3.4 Pseudo requirements Our system will target PDAs and PCs with wireless networking capability (desktops or laptops). The server version and the client version of the program will run on the same device, which would use Windows NT ™ or Windows CE ™ as operating system. For multimedia operations and for the player interface, Windows Media Player 9 Series ™‘s SDK will be used along with .NET environment and C# programming language of Microsoft. 3.5 System models 3.5.1 Scenarios Scenario1 (Server Side): • The user starts the server application. • Enters the settings menu and adjusts the maximum number of connections to 5. • Puts two files in “C:Media” folder to the sharing list. • Starts the server. • 3 client users connect to the server and start streaming. • The user realizes some problem of the third client user. • Cancels third client user’s streaming and adds him to block list. Scenario 2: • The user starts the client application. • Searches for the waiting servers in the connection range. • Sees that there are three servers that are ready for streaming. • Decides to use the first server named “Tuncer” and requests the media shared by that server. • Finds 3 mpg videos. 12
  13. 13. Bilkent University – Department of Computer Engineering • Selects “The best goal ever.mpg” from the list. • Starts to watch from the beginning. • When it was at the middle of the video he decides to pause the streaming video. • Seeks a few seconds backwards. • Presses play button to continue playing. • After watching the video closes the application. Scenario 3: • The user starts the client application. • Enters the IP address of the specific server called “Emrah”. • Sees that there are 5 mpg and 3 mp3 media files in the list. • Selects “Kurtlar Vadisi - Cendere.mp3” from the list under audio folder. • Presses stop button when 2:45 minutes past. • Closes the application. 3.5.2 Use case model Figure 3.5.2.1: Client side streaming media use case model 13
  14. 14. Bilkent University – Department of Computer Engineering Figure 3.5.2.2: Server side use case model Figure 3.5.2.3: Client side server connection/settings use case model 14
  15. 15. Bilkent University – Department of Computer Engineering 3.5.3 Dynamic models Figure 3.5.3.1: Server side model 15
  16. 16. Bilkent University – Department of Computer Engineering Figure 3.5.3.2: Client side server search model 16
  17. 17. Bilkent University – Department of Computer Engineering Figure 3.5.3.3: Client side media streaming control model When user starts streaming of the media, the streaming component is set to Buffering state. After enough data received from the server the state is set to Playing and the application starts playing the media. If user presses stop button in Playing or Buffering state, the state will be set to Stop and streaming stops immediately. If user presses pause button in Playing or Buffering states the state is set to Pause, streaming pauses, and the frame of the current stream is preserved. If user presses play button in stop state or Pause state the state is set to Buffering. Throughout playing process if data can not be received as fast as needed, the state is set to Buffering again or if no data comes or connection is lost, Stop state is set. While playing if user seeks on the seeking bar the state is set to Buffering. If user closes stream at any state in any way, stating mechanism ends. 17
  18. 18. Bilkent University – Department of Computer Engineering 3.5.4 User interface - navigational paths and screen mock-ups Figure 3.5.4.1: Client side connection options Figure 3.5.4.2: Client side contents page Figure 3.5.4.3: Client side streaming media frame 18
  19. 19. Bilkent University – Department of Computer Engineering 4. Glossary Bandwidth: In computer networks, bandwidth is often used as a synonym for data transfer rate - the amount of data that can be carried from one point to another in a given time period (usually a second). This kind of bandwidth is usually expressed in bits (of data) per second (bps). IEEE 802.11: 802.11 is an evolving family of specifications for wireless local area networks (WLANs) developed by a working group of the Institute of Electrical and Electronics Engineers (IEEE) RTP: The Real-Time Transport Protocol (RTP) is an Internet protocol standard that specifies a way for programs to manage the real-time transmission of multimedia data over either unicast or multicast network services. Originally specified in Internet Engineering Task Force (IETF) Request for Comments (RFC) 1889, RTP was designed by the IETF's Audio-Video Transport Working Group to support video conferences with multiple, geographically dispersed participants. RTP is commonly used in Internet telephony applications. RTP does not in itself guarantee real-time delivery of multimedia data (since this is dependent on network characteristics); it does, however, provide the wherewithal to manage the data as it arrives to best effect. Streaming Media: Streaming media is sound (audio) and pictures (video) that are transmitted on the Internet in a streaming or continuous fashion, using data packets. The most effective reception of streaming media requires some form of broadband technology such as cable modem or DSL. UDP: UDP (User Datagram Protocol) is a communications protocol that offers a limited amount of service when messages are exchanged between computers in a network that uses the Internet Protocol. Like the Transmission Control Protocol, UDP uses the Internet Protocol to actually get a data unit (called a datagram) from one computer to another. Unlike TCP, however, UDP does not provide the service of dividing a message into packets (datagram) and reassembling it at the other end. Specifically, UDP doesn't provide sequencing of the packets that the data arrives in. This means that the application program that uses UDP must be able to make sure that the entire message has arrived and is in the right order. TCP: TCP (Transmission Control Protocol) is a set of rules (protocol) used along with the Internet Protocol (IP) to send data in the form of message units between computers over the Internet. While IP takes care of handling the actual delivery of the data, TCP takes care of keeping track of the individual units of data (called packets) that a message is divided into for efficient routing through the Internet. Wireless: Wireless is a term used to describe telecommunications in which electromagnetic waves (rather than some form of wire) carry the signal over part or the entire communication path. 19
  20. 20. Bilkent University – Department of Computer Engineering 5. References 1. http://grouper.ieee.org/groups/802/11/index.html 2. http://en.wikipedia.org/wiki/Main_Page 3. http://whatis.techtarget.com/ 4. http://msdn.microsoft.com/vcsharp/ 5. http://www.apple.com/quicktime/technologies/streaming/ 6. http://www.microsoft.com/windows/windowsmedia/forpros/streaming.aspx 7. http://www.microsoft.com/windows/windowsmedia/forpros/mobilemedia.aspx 8. http://www.microsoft.com/windows/windowsmedia/mp10/sdk.aspx 9. https://helixcommunity.org/ 10. http://www.shoutcast.com/ 20

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