Chapter 2 The OSI Model and TCPIP Protocol

Chapter 2 The OSI Model and TCP/IP Protocol Suite Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

CONTENTS • THE OSI MODEL • LAYERS IN THE OSI MODEL • TCP/IP PROTOCOL SUITE • ADDRESSING • TCP/IP VERSIONS Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

2. 1 THE OSI MODEL Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

ISO is the organization. OSI is the model. Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -1 OSI Model Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -2 Mc. Graw-Hill OSI layers ©The Mc. Graw-Hill Companies, Inc. , 2000

Headers are added to the data at layers 6, 5, 4, 3, and 2. Trailers are usually added only at layer 2. Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -3 Mc. Graw-Hill An exchange using the OSI model ©The Mc. Graw-Hill Companies, Inc. , 2000

2. 2 Mc. Graw-Hill LAYERS IN THE OSI MODEL ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -4 Physical Layer Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Physical layer • • 1. 2. 3. 4. 5. 6. 7. Mc. Graw-Hill responsible for movements of individual bits from one hop to the next The physical layer also concern with the following: Physical characteristics of interface and medium. Representation of bit: define the type of encoding. Data rate : the number of bit sent each second. Synchronization of bits: it must be synchronized at the bit level Line configurations : concerned with the connection of devices to the media. Physical topology: how device can connected to make a network. Transmission mode: define the direction of transmission ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -5 Data Link Layer Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Data link • • 1. 2. 3. 4. Mc. Graw-Hill responsible for moving frame from one node to the next. Other responsibilities to the data link layer : Framing. Physical addressing. Flow control. Error control. ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -6 Node-to-node delivery Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -7 Network Layer Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Network layer • The network layer is responsible for the delivery of individual packets from the source host to the destination host. • other responsibilities of the network layer include the following : 1. Logical addressing 2. routing Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -8 Mc. Graw-Hill End-to-end delivery ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -9 Mc. Graw-Hill Transport Layer ©The Mc. Graw-Hill Companies, Inc. , 2000

Transport layer • • 1. 2. 3. 4. 5. Mc. Graw-Hill the transport layer is responsible for the delivery of the message from one process to another. Other responsibilities of the transport layer: Service- point addressing. Segmentations and reassembly. Connection control. Flow control. Error control. ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -10 Reliable end-to-end delivery of a message Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -11 Session Layer Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Session layer • The session layer is the network dialog controller • It establishes, maintains and synchronizes the interaction between communicating system. Specific responsibilities of the session layer: 1. dialog control : allows two system to enter a dialog. 2. synchronization point. Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -12 Presentation Layer Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Presentation layer • concerned with the syntax and semantics of the information exchanged between two systems. • Specific responsibilities of the presentation layer: 1. Translation 2. Encryptions 3. Compression Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -13 Application Layer Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Application layer • • 1. 2. 3. 4. Mc. Graw-Hill Enable the user , whether human or software to access the network. Specific services provided by the application layer network virtual terminal File transfer , access and management Mail services directory services ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -14 Summary of layers Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

2. 3 Mc. Graw-Hill TCP/IP PROTOCOL SUITE ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -15 Mc. Graw-Hill TCP/IP and OSI model ©The Mc. Graw-Hill Companies, Inc. , 2000

2. 4 ADDRESSING Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -16 Addresses in TCP/IP Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -17 Mc. Graw-Hill Relationship of layers and addresses in TCP/IP ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -18 Physical addresses Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Example 2 Most local area networks use a 48 -bit (6 bytes) physical address written as 12 hexadecimal digits, with every 2 bytes separated by a hyphen as shown below: 07 -01 -02 -01 -2 C-4 B A 6 -byte (12 hexadecimal digits) physical address Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -19 IP addresses Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Example 4 As we will see in Chapter 4, an Internet address (in IPv 4) is 32 bits in length, normally written as four decimal numbers, with each number representing 1 byte. The numbers are separated by a dot. Below is an example of such an address. 132. 24. 75. 9 Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

Figure 2 -20 Mc. Graw-Hill Port addresses ©The Mc. Graw-Hill Companies, Inc. , 2000

Example 6 As we will see in Chapters 11 and 12, a port address is a 16 -bit address represented by one decimal number as shown below. 753 Mc. Graw-Hill A 16 -bit port address ©The Mc. Graw-Hill Companies, Inc. , 2000

2. 5 TCP/IP VERSIONS Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000

IP Versions: • Version 4 (current) The primary problem is that the Internet address is only 32 bits • Version 6 (future) Use 128 bit addresses Mc. Graw-Hill ©The Mc. Graw-Hill Companies, Inc. , 2000