Networking Media

1. Networking Media Chapter 1 All Material Taken from Faster Smarter Network+ Certification by Melissa Craft

2. Topologies • Physical Topologies • Point-to-point connections • Multipoint connections • Logical Topologies • How does the data flow?

3. Physical Star Topology • A central hub connects to each device • Central hub can also be a switch, multipoint repeater, or Multi-station Access Unit (MAU or MSAU) • Most common topology

4. Physical Bus Topology • Single cable used to connect multiple devices with termination at both ends

5. Physical Mesh Topology • All devices are connected to each other Full mesh topology

6. Hierarchical Mesh Topology • Devices are not connected directly to every other device, but a connection path can be made.

7. Physical Ring Topology • Closed loop of cabling connecting each device in a ring. • Data can flow in either direction, depending on configuration.

8. Wireless Topology • Areas capable of transmitting data arranged in cells • Access points are used

9. Logical Ring Topology • Physically a star, but data flows in one direction, thus creating a circular path for data

10. Cellular Topology • Basically a logical bus topology • Devices can seamlessly move between cells • See P. 16 in text

11. Accessing the Media • Contention • CSMA/CD • CSMA/CA

12. CSMA/CD • Carrier Sense Multiple Access/Collision Detection • Walking in without ringing the bell! • Just make sure the door is open, even if someone else is in the doorway. • When a collision occurs, each sending device must resend the message.

13. CSMA/CD (cont.) • Advantages • Easy to implement • Requires few resources • Very fast when traffic is light • Disadvantages • Speed can decrease significantly in high traffic • Only detects collisions…doesn’t avoid them • All data is treated equally

14. CSMA/CA • Carrier Sense Multiple Access/Collision Avoidance • Ring the bell before entering! • If someone is in the doorway, wait for them to get out of the way. • Uses special contention protocols and time slices

15. CSMA/CA (cont.) • Advantages • Less administrative overhead than CSMA/CD • Allows more messages to be seemingly sent simultaneously by using time slices • Significantly reduces collisions, increases data throughput • Disadvantages • Collisions still occur • All data still treated equally

16. Token Passing • If you don’t have it, you can’t get in! • A special data packet (token) is passed around the network • Only the device which has the token can transfer data

17. Token Passing (cont.) • Advantages • No data collisions! • Highest amount of data throughput in high traffic networks • Utilizes demand priority (not all data is treated equally)

18. Token Passing (cont.) • Disadvantages • Much more expensive to implement • Requires more processing power to deal with the token • Each device must be aware of its neighboring devices so that the token can be received & passed along • Low data throughput in low traffic networks • Low priority data can have trouble being sent

19. Media Types • Unshielded Twisted Pair (UTP) • Uses twisted pairs of wires • Subject to crosstalk • See table on p. 21 • Shielded Twisted Pair (STP) • Heavy outer covering (shield) • Much more resistant to noise • More expensive • Difficult to install due to lack of flexibility

20. Coaxial Cable • Standard Cable TV cable • Copper conductor surrounded by insulation • Braided or mesh outer cover surrounds the insulation (also a conductor) • PVC plastic jacket encases cover

21. ThickNet (RG-8) • Older type of coaxial cable • Physical bus topology • Very thick shielding • Difficult to work with because it is so rigid • 50 ohm terminators at both ends of bus • Uses vampire tap connectors

22. ThinNet (RG-58) • Much more flexible than ThickNet • Physical bus • Maximum of 30 devices on 185 meter length of cable • BNC connectors are crimped onto the cable for connectivity • Terminators at both ends

23. Fiber Optic Cable • Thin strand of glass enclosed in a glass tube • Shielded with PVC plastic • Very brittle, not very flexible • Immune to crosstalk • Supports very long distances • Requires specialized installation • More expensive option

24. Wireless Media • IEEE 802.11 specification • Radio frequency (RF) 2.4 gigahertz range for wireless data transmissions • Data rate depends upon type of protocol implemented. (802.11-B, 802.11-G) • No cables, easy to install & configure • Poor security • Distance can be limited

25. Media Connectors • RJ-11 • Common telephone connector • RJ-45 • Most common network connection type • Looks like a “fat” telephone connector

26. Media Connectors • AUI (Attachment Unit Interface) • Used in ThickNet and ThinNet cables • 15 pins on the end that connects to the network interface card. (NIC) • Other end connects to a short cable which connects to a transceiver, which connects to the main cable. Transceiver AUI

27. Media Connectors • BNC (British Naval Connectors) • Used in ThinNet 10Base2 Ethernet • Resemble cable TV connectors

28. Media Connectors • ST • Used in duplex fiber optic connections

29. Media Connectors • SC • Used in simplex fiber optic connections

30. Media Connectors • RS-232 • 9 or 25 pins connectors • Used only in serial communications with analog modems

31. IEEE Specifications • 802.2 (LLC) • Logical Link Control • Protocol Specification used by all 802 standards

32. IEEE Specifications • 802.3 (Ethernet) • 10BaseT • 10Base2 • 10Base5

33. IEEE Specifications • 802.3u (Fast Ethernet) • 100BaseT

34. IEEE Specifications • 802.4 • Token Bus • 802.5 • Token Ring

35. IEEE Specifications • 802.6 • Metropolitan Area Networks (MAN) based on bidirectional fiber optic bus

36. IEEE Specifications • 802.11(a & b) • Wireless networks

37. FDDI • Fiber Distributed Data Interface • Dual ring topology (uses token passing) • If one ring fails, the other takes over • Good for long distances • Large data capacity