CS 447 Networks and Data Communication

1. Network Protocols, Interfaces, and OSI 7-Layer Reference Model CS 447 Networks and Data Communication Department of Computer Science Southern Illinois University Edwardsville Fall, 2019 Dr. Hiroshi Fujinoki E-mail: hfujino@siue.edu

2. Computer A Computer B Application Program Application Program Network Protocol Network Protocol Wire (Computer Network) CS 447 Networks and Data Communication Organization of a Computer Connected to a Computer Network Network Protocol/001

3. Definitions Example CS 447 Networks and Data Communication A network protocol is:  a set of rules  that governs communication between two hosts  implemented as software - MS NetBEUI - TCP - IP - etc. - IPX/SPX Network Protocol/002

4. Interface: a set of rules that governs communication between two directly facing protocol layers Protocol and Interface Computer A Computer B Application Program Application Program Protocol TCP TCP IP IP MAC MAC Interface Protocol Stack Wire (Computer Network) CS 447 Networks and Data Communication Network Protocol/003

5. Summary CS 447 Networks and Data Communication • A network protocol is a set of rules that govern communication between • two host computers (in the same level) • An interface is a set of rules that govern communication between • two directly facing protocol layers (within a host computer) Network Protocol/004

6. “End-to-end” and “point-to-point” Point-to-point NIC Intermediate Routers Host A Host B End-to-end CS 447 Networks and Data Communication OSI_SevenLayer/001

7. OSI Seven Layer Model Application Program Purposes Interface to user programs Layer 7 Layer 6 Data filters (compression, encryption) Layer 5 Manage end-to-end connection Provide reliable end-to-end connection Layer 4 Manage point-to-point connection Layer 3 Layer 2 Provide reliable point-to-point connection Layer 1 Dealing with electric signals NIC signals Wire (Network Cable) CS 447 Networks and Data Communication Application Layer Presentation Layer Session Layer Transport Layer Network Layer Datalink Layer Physical Layer OSI_SevenLayer/002

8. Layer 1: Physical Layer • Manchester Signal Encoding • NRZI Signal Encoding • Bipolar-AMI Signal Encoding Define how the signals are represented CS 447 Networks and Data Communication Major Function: Dealing with electric signals Example: • Interpret electric signals, represent them as 1’s or 0’s OSI_SevenLayer/003

9. Layer 2: Data Link Layer  Star (=hub)  Bus  Ring CS 447 Networks and Data Communication Major Functions: • Try to detect and correct signal errors, if any • Forward the received signals to the network layer • If uncorrectable errors, gives an error warning to the network layer • Provide Media Access Control (MAC) - For “shared” network, control who can use the network first Examples of Shared Network: OSI_SevenLayer/004

10. - Establisha connection Layer 3: Network Layer - Keep track ofthe sequence number - Continue tocheck the statusof a connection - Delete a connection when it is done CS 447 Networks and Data Communication Major Function: • Maintain an point-to-point connection OSI_SevenLayer/005

11. Layer 4: Transport Layer - If the receiver wants to slow down, reduce transmission rate - If the network is congested, reduce the transmission rate Major Functions: • Establish/Manage/Delete (E2E) connections Layer 5: Session Layer • Full-Duplex/Half-Duplex Control • QoS (specify maximum tolerable delay) CS 447 Networks and Data Communication Major Functions: • Try to detect and correct packet errors (error control) for E2E • Perform flow control OSI_SevenLayer/006

12. Compression Encryption Encrypted Data Presentation Layer Presentation Layer Raw Data Raw Data Layer 6: Presentation Layer Layer 7: Application Layer Compressed Data CS 447 Networks and Data Communication Major Functions: Encryption, compression, etc Major Function: Interface to your application programs Example: Network API (Application Program Interface) OSI_SevenLayer/007

13. NFS (Network File Server) Telnet, FTP, SMTP, rlogin, DNS, HTTP, rcp, finger, etc. XDR (External Data Rep.)  RPC (Remote Proc. Call)  TCP UDP  IP ARP RARP Network Hardware  CS 447 Networks and Data Communication TCP/IP Protocol Suite: Application Layer Presentation Layer Session Layer Transport Layer Network Layer Datalink Layer Physical Layer OSI_SevenLayer/008

14. Full-Duplex Circuit NIC at host B Full-Duplex and Half-Duplex Transmitting Circuit Transmitting Circuit Receiving Circuit Receiving Circuit NIC at host A Multiplexer CS 447 Networks and Data Communication Full-duplex: a connection two host can talk simultaneously Half-duplex: a connection one of the two hosts can talk at a time OSI_SevenLayer/009

15. Half-Duplex Circuit Transmitting Circuit Receiving Circuit Switch CS 447 Networks and Data Communication NIC at host B Transmitting Circuit Receiving Circuit NIC at host A Half-duplex: One-way communication at a time OSI_SevenLayer/009