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Networking in UNIX

Networking in UNIX. A brief review and frequently used commands. 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. Common Network Terminology. LAN

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Networking in UNIX

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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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