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Networking in UNIX: A Brief Review and Frequently Used Commands

Gain a comprehensive understanding of networking concepts in UNIX, covering network terminology, Ethernet basics, routers, protocols, and application layers. Explore frequently used commands for user management, hostname, finger, write, talk, walk, and mail in UNIX.

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Networking in UNIX: A Brief Review and Frequently Used Commands

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  1. Networking in UNIX A brief review and frequently used commands

  2. 1.Overview of Network Concept • A network is an interconnected system of cooperating computers. • UNIX had a huge explosion of network applications in early 1990’s. • Example: Clients-server systems

  3. Common Network Terminology • LAN • WAN • INTERNET • WWW

  4. Different Topologies • BUS • RING • STAR

  5. Ethernet • First developed by Xerox Corporation. • It works like this: • 1. Each computer contains an Ethernet card, and each card has a unique Ethernet address. • 2. Every computer’s Ethernet card is connected to the same single piece wire (Ethernet cable).

  6. Ethernet… • 3. A computer broadcasts its message onto the Ethernet a particular Ethernet address along with Ethernet header and trailer information. Only that computer Ethernet card has the same address accepts the message. • 4. In case of collision-two or more computers broadcast to the Ethernet at the same time, they will wait a random period of time and then try again.

  7. Ethernet… Ethernet Cable • .

  8. Bridges • Because there is a length limit on how long an Ethernet cable can be, we need some special devices to connect different Ethernet network together when the limit is exceeded. • Ethernet Standard: IEEE 802.3 • See document: TechFest on my web site

  9. Cable Bus Length Limit • See Document: Cable Buses on my web site

  10. Diagram • .

  11. Routers • Routers are introduced to connect multi-LANs together in a more efficient way. • Example: Connect four LAN together.

  12. Gateways • To connect several LAN into a single large wide area network (WAN), we need several high-capacity routers, which we call gateways to realize this goal. • Example: Each corporation (a University can be considered as a corporation) tie their LAN through the nearest gateway.

  13. Protocols • TCP/IP • Transmission Control and Internet Protocols

  14. The Five-Layer TCP/IP Internet Protocol Hierarchy

  15. Physical Layer • Protocols govern the exchange of binary digits across a physical communication channel • Goal: create a “bit pipe” between two computers

  16. Data Link Layer • Protocols carry out • Error handling • Framing • Creates an error-free “message pipe” • Composed of two services • Layer 2a: medium access control • Layer 2b: logical link control

  17. Data Link Layer (continued) • Medium access control protocols • Determine how to arbitrate ownership of a shared line when multiple nodes want to send at the same time • Logical link control protocols • Ensure that a message traveling across a channel from source to destination arrives correctly

  18. Network Layer • Delivers a message from the site where it was created to its ultimate destination • Critical responsibilities • Creating a universal addressing scheme for all network nodes • Delivering messages between any two nodes in the network

  19. Network Layer (continued) • Provides a true “network delivery service” • Messages are delivered between any two nodes in the network, regardless of where they are located • IP (Internet Protocol) layer • Network layer in the Internet

  20. Transport Layer • Provides a high-quality, error-free, order preserving end-to-end delivery service • TCP (Transport Control Protocol) • Primary transport protocol on the Internet • Requires the source and destination programs to initially establish a connection

  21. Application Layer • Implements the end-user services provided by a network • There are many application protocols, including: • HTTP • SMTP • POP3 • IMAP • FTP

  22. Some Popular Application Protocols on the Internet

  23. Application Layer (continued) • Uniform Resource Locator (URL) • A symbolic string that identifies a Web page • Form protocol://host address/page • The most common Web page format is hypertext information • Accessed using the HTTP protocol

  24. Internet Address • An IP address is a 32-bits value that is written as four dot-separated numbers (4 dot-separated bytes) from 0-255 • Newer IPv6 will define 128-bit IP addresses.

  25. UNIX Utilities on Networking • 1. users

  26. Who And W • who – displays every user on your local host. • w – similar to who and it gives you a little more information on each user.

  27. hostname • hostname – displays the name of your local host

  28. finger • finger [userid] displays information about a list of users with more information. • Example: finger zhang • Pay attention about the extra information it displays.

  29. Write, talk, walk, and mail • write – sending a line a time • You already saw talk and walk briefly before. • mail is an old command we used a lot even before the WWW

  30. The mesg command • If one does not want be bothered with the public information (it almost like the pop-ups in the Internet), one can disable them by set the mesg n command. • Example: mesg n or mesg y

  31. ftp command

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