CH. 2 Network Models

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1 Islamic University of Gaza Faculty of Engineering Computer Engineering Department Data com. Discussion ECOM 4014 Lecture # 2 CH. 2 Network Models By Eng. Wafaa Audah Sep. 2013

OSI Model Open Systems Interconnection (7-Layers) الشكل المقابل يمثل توزيع ال layers وترتيبها باآللية التي يمثلها ال OSI - Every layer serve its upper layer.

2 OSI Model Open Systems Interconnection (7-Layers) الشكل المقابل يمثل توزيع ال layers وترتيبها باآللية التي يمثلها ال OSI - Every layer serve its upper layer. - Peer-peer process: كم layer ترع ف عه انذاذا - انهه واصهح نها ي ال layer انه فىقها header هادا انه ذر ت كى ت ذرى عذج شغالخ يه ح دسة ال layer انه ظافرى. آن ح االظافح تركى تانذزكح ي االعه نألسفم ع ذ ان زسم وي االسفم ان االعه ع ذ ان سرقثم ونك تاخرالف ا ى ع ذ ان سرقثم ت رى انذذف او االسانح نهادا ال header فثانران يذرىي انثاك د او انه واصم كم غثقح ع ذ ان زسم رح كى فسى ع ذ ان سرقثم ته ك ت كى انرىاصم وكأ ى صار ت كم غثقح ويث هرها ي ان اد ر تغط ان ظز شى صارتانطز ق ت هى. * بيكىن في الشبكة بيه المرسل والمستقبل intermediate nodes -عه سث م ان ثال router ت كى ذعايم هادا انزاوذز وانرىاصم يعى ي خالل انثالز غثقاخ االون ي االسفم وانه ت س هى انطثقاخ انذاع ح نهشثكح. ايا تان سثح ل switch فث ع م تس عاول غثقر ي االسفم. 2

3 اضافة الهيدرز مه الطبقات السفلية بيكىن كالتالي 3

4 The Physical Layer - The physical layer is responsible for ensuring that a stream of bits is transmitted between two nodes sharing a single link. - The physical layer coordinates all the functions required to transmit a bit stream over the physical medium. - Data rate: Transmission rate number of bits sent per second - Synchronization of bits. هذا ع ا ان زسم وان سرقثم جة ا سرع هى فس ال data rate ك ا أ عا جة ا رى قم انثراخ دسة ال clock ترشاي ت ان زسم وان سرقثم نع ا قم انثراخ تانرزذ ة وانىقد انصذ خ. The Data Link Layer - The data link layer is responsible for ensuring that a packet of data is successfully transmitted between two adjacent nodes in the network. - Flow control: Prevent overwhelming the receiver. - Error control: Detect and retransmit damaged or lost frames; Prevent duplication of frames; using trailer. Hop-to-hop (node-to-node) delivery: add physical address as a header, also add a tailor for error control. Network Layer The network layer is responsible for the delivery of packets from the original source to the final destination. The responsibilities of the network layer: - Logical addressing. - Routing: 4

5 Transport Layer The transport layer is responsible for delivery of a message from one process to another. Responsibilities of the transport layer - Port addressing - Flow control - Error control Session, presentation layers (according to the Dr s recommendations) are not important Application Layer The application layer is the interface between the user and the network (session, presentation and application layers are user support layers) Some of services - Network virtual terminal: Logon to a remote host. - File transfer, access, and management. - Mail services TCP/IP Protocol Suite (Internet Model) 5

6 Packet or Stream of bits The most important protocols according to the layers ADDRESSING There are four levels of addresses are used in an internet employing the TCP/IP protocols. 6

7 Physical Address (يرغ ز و ثم ع ىا انه ك انران ون س ان سرقثم ان هائ ( address Link Logical Address (ثاتد و ثم ان زسم وان سرقثم ان هائ ) Universal addressing Port Address Processes addresses Specific Address Text-Book Questions Review Questions 2. Which layers in the Internet model are the network support layers? The network support layers are the physical, data link, and network layers. 3. Which layer in the Internet model is the user support layer? The application layer supports the user. 7. What are headers and trailers, and how do they get added and removed? Headers and trailers are control data added at the beginning and the end of each data unit at each layer of the sender and removed at the corresponding layers of the receiver. They provide source and destination addresses, synchronization points, information for error detection, etc. 7

Exercises 16. Match the following to one or more layers of the OSI model: a. Route determination: Network Layer b. Flow control: Data link, Transport Layers c.

8 Exercises 16. Match the following to one or more layers of the OSI model: a. Route determination: Network Layer b. Flow control: Data link, Transport Layers c. Interface to transmission media: Physical Layer d. Provides access for the end user: Application Layer 20. In Figure 2.22, computer A sends a message to computer D via LANl, router Rl, and LAN2. Show the contents of the packets and frames at the network and data link layer for each hop interface. حسب الشرح السابق واضافة كل طبقة للهيدرز الخاصة بها الحل هى كالتالي: 8

ع كى 21. In Figure 2.22, assume that the communication is between a process running at computer A with port address i and a process running at computer D with port address j.

9 ع كى 21. In Figure 2.22, assume that the communication is between a process running at computer A with port address i and a process running at computer D with port address j. Show the contents of packets and frames at the network, data link, and transport layer for each hop. 22. Suppose a computer sends a frame to another computer on a bus topology LAN. The physical destination address of the frame is corrupted during the transmission. What happens to the frame? How can the sender be informed about the situation? If the corrupted destination address does not match any station address in the network, the packet is lost. If the corrupted destination address matches one of the stations, the frame is delivered to the wrong station. In this case, however, the error detection mechanism, available in most data link protocols, will find the error and discard the frame. In both cases, the source will somehow be informed using one of the data link control mechanisms discussed in Chapter 11. انع او ادذ ىافق انخهم ياصار تعذ انجذ ذ ان ىجىدج ع ا ادر ان ه ا ايا ا انع ىا تانران رح ذىصم انذاذا تس نهع ىا انغهػ!! ايا االدر ال ذع ع يا ىافق ا ى فهى انرا ع ىا ا ا انع ىا نسر ش يىجىدج تانران انثاك د ان زسهح detection تانذانر يفزوض كى ف ي ثىد خاصح ب error نهذاذا وذع ذ ارسانها تشكم صذ خ انغاء وذع م ا زور ا ى صار ذعزف السو See You at Next lecture Best Wishes 9

ES623 Networked Embedded Systems

ES623 Networked Embedded Systems Introduction to Network models & Data Communication 16 th April 2013 OSI Models An ISO standard that covers all aspects of network communication is the Open Systems Interconnection