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

Real World Example Communication between managers of two companies Communicate

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

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

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

Responsible for providing services to the user Application Layer Responsible for providing services to the user The only layer to interact with user Data Data Logical communication Application Layer SMTP FTP HTTP SMTP FTP HTTP Data H5 Data H5 to Transport from Transport

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

Transport Layer Data Data Transport Layer (segments) to Network App-A App-B App-C Sending Host App-A App-B App-C Receiving Host Data Data Transport Layer Data1 H4 Data2 H4 Data3 H4 Data1 H4 Data2 H4 Data3 H4 (segments) to Network from Network

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

Network Layer from Transport to Transport Data Data Network Layer Data H3 Data H3 (packet) to Data Link from Data Link

Network Layer A1, A2, B1, B3, ... are logical addresses A1 A2 Data A1 C7 A1, A2, B1, B3, ... are logical addresses A1 A2 Network A R1 B1 Network B B6 B3 R3 R2 C2 Router D3 Network C C7 Network D D8

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

Data Link Layer from Network to Network Data Data Data Link Layer T2 H2 T2 Data H2 (frame) to Physical from Physical

Data Link Layer 10, 35, 82, 97, ... are physical addresses Data 97 35

Data Link Layer A1 A2 97 32 Network A 25 R1 B1 79 Network B B6 B3 62 C7 A1 A2 97 32 Network A 25 Data A1 C7 97 25 R1 B1 79 Network B Data A1 C7 79 62 B6 B3 62 12 R3 R2 C2 54 88 D3 Data A1 C7 54 74 Network C C7 74 Network D D8

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

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

Internet Protocol Suite Layer Protocols Application HTTP, FTP, Telnet, SMTP, ... Transport TCP, UDP, SCTP, ... Network IP (IPv4), IPv6, ICMP, IGMP, ... Data Link Ethernet, Wi-Fi, PPP, ... Physical RS-232, DSL, 10Base-T, ...