Network Models CCNA Instructor Training Course October 12

Network Models CCNA Instructor Training Course October 12 -17, 2009 Department of Computer Engineering Kasetsart University 1

Real World Example n Communication between managers of two companies Communicate 2

What Actually Happens n Communication takes place thru many layers Logical communication Secretary: types a letter Delivery boy: drops the letter Secretary: reads and reports the message Delivery boy: takes the letter Postal truck Post office: Processes and routes the letter 3

Internet Model n The Internet Protocol Stack User Application Layer Software Transport Layer Network Layer Data Link Layer Network Access Physical Layer Hardware Transmission Medium 4

Internet Model router sender router receiver Application Transport Network Data Link Physical Transmission medium 5

Application Layer Responsible for providing services to the user n The only layer to interact with user Data Application Layer SMTP FTP Data Logical communication HTTP H 5 to Transport SMTP Data FTP Data HTTP H 5 from Transport 6

Transport Layer Responsible for delivery of a message from one process to another n Duties/services Port addressing n Segmentation and reassembly n Connection control n Flow control (end-to-end) n Error control (end-to-end) n 7

Transport Layer Sending Host App-A App-B App-C Data Transport Layer Data 1 H 4 Data 2 H 4 Data 3 H 4 Receiving Host App-A App-B App-C Data 1 H 4 Data 2 H 4 Data 3 H 4 (segments) to Network from Network 8

Network Layer Responsible for the delivery of packets from the original source to the destination n Duties/services Logical addressing n Routing n 9

Network Layer from Transport to Transport Data Network Layer Data H 3 (packet) to Data Link from Data Link 10

Network Layer Data A 1 C 7 A 1, A 2, B 1, B 3, . . . are logical addresses A 2 Network A R 1 B 6 Network B B 3 R 2 Router C 2 D 3 C 7 D 8 Network C Network D 11

Data Link Layer Responsible for transmitting frames from one node to the next n Duties/services Framing n Physical addressing n Flow control (hop-to-hop) n Error control (hop-to-hop) n Access control n 12

Data Link Layer from Network to Network Data Link Layer T 2 Data H 2 (frame) to Physical from Physical 13

Data Link Layer 10, 35, 82, 97, . . . are physical addresses Data 97 T 2 Data 35 97 82 10 10 H 2 14

Data Link Layer Data A 1 C 7 A 1 97 A 2 32 Data A 1 C 7 97 25 Network A 25 R 1 B 1 79 12 Network B Data A 1 C 7 79 62 B 6 B 3 62 R 3 R 2 C 2 54 88 D 3 D 8 Network D Data A 1 C 7 54 74 C 7 74 Network C 15

Physical Layer Responsible for transmitting individual bits from one node to the next n Duties/services Physical characteristics of interfaces and media n Representation of bits n Data rate (transmission rate) n Synchronization of bits n 16

Physical Layer from Data Link Physical Layer to Data Link Data 01001011 (bits) Transmission medium 17

Internet Protocol Suite Layer Protocols Application HTTP, FTP, Telnet, SMTP, . . . Transport TCP, UDP, SCTP, . . . Network IP (IPv 4), IPv 6, ICMP, IGMP, . . . Data Link Ethernet, Wi-Fi, PPP, . . . Physical RS-232, DSL, 10 Base-T, . . . 18