1. Chapter 15 Network Hardware Unix System Administration

2. If VirtualRatings.Com Had Student Ratings, You’d Get a 10 Network technologies & topologies –Ethernet - bus, star –Token-Ring –FDDI - ring –ATM - star Networking Devices –Hubs –Bridges/switches –Routers

3. You’ve Got Some Nice Toplogies Ethernet –Bus technology –Can be wired in a bus or physical star topology –The Polite Dinner Party - CSMA/CD Carrier sense Multiple access Collision detection –Hubs, switches, bridges and routers

4. Wirez Wire Thicknet –10Base5 - 50 ohm RG-11 –Vampire Taps connect drop cable to thicknet –Max length = 117m with 2.5m between devices Thinnet –10Base2 - 50 ohm RG-58 –BNC T connectors –Max length = 185m

5. Twisting The Au Pairs Star configs using hubs or switches Wires are twisted to compensate for cross- talk - Don’t use a regular phone cable Two pairs (4-wires) are used even though four pair cable is usually installed RJ-45 connector pins 1,2,3 & 6 are used Cabling is rated in levels –Level III (3) is for up to 10Mbps –Level V is for up to 100Mbps

6. How About More Fiber In Your Diet? Fiber cable is basically a piece of glass covered with a reflective cladding Fiber devices are always configured in a star (point-to-point) Fiber is either multi-mode or single-mode I wouldn’t waste fiber on anything less than 100Mbps. Currently Gigabit Ethernet is only available using fiber. SX-short wave, LX-long wave

7. Do It Yourself Laser Eye Surgery Fiber-optic safety –Be Careful not to stick yourself with a broken fiber –Two types of signal source, LED and LASER –NEVER look into a fiber cable if you don’t know what’s connected to the other end

8. Is That a Token In Your Ring, or Are You Just Happy To See Me? Token-Ring use a token passing scheme that guarantees each device gets a chance to transmit data FDDI works similar to token-ring but uses fiber-optics in a 100Mbps dual counter- rotating ring configuration –Good at surviving a single ring cut –Expensive

9. ATM, Your PIN # Please Asynchronous Transfer Mode For voice, video and data transmissions Uses 53-byte cells instead of packets in a switching network similar to a telephone system. Never really took off in a LAN environment but is very popular in the WAN or backbone Feature QoS and RSVP Big learning curve over Ethernet technologies

10. Hubs and Switches and Routers, Oh My! Hubs –Basically a multi-port repeater –Ethernet limits repeaters to 4 per segment –Each hub counts as a single repeater –Modern hubs usually have a way to connect them without incurring a repeater hop –Hubs being replaced by inexpensive switches –I wouldn’t suggest a hub except in the most trivial network setup

11. Bridges, Switches. What’s The Difference? Bridge connects multiple segments of a network together Bridges can also connect differing topologies (e.g. token-ring & Ethernet) Switches are fast bridges Bridges and switches work at layer 2 of the OSI model (data link) which means decisions are based on MAC addresses

12. Routers Schmouters Routers connect networks/IP subnetworks together. Routers work at Layer 3 of the OSI model (Network) Routers are smart and can make decisions based on IP (or IPX) addresses and can filter based on TCP/UDP port numbers

13. Trans-topological Devices Layer 3 Switches –a.k.a. fast routers –Routes IP/IPX/Appletalk only –VLANS (port, protocol or network-based) Layer 4 Switches/Routers –Makes decisions based on protocol content, e.g. URL

14. If You Slept Through Everything Else, Pay Attention Now

15. 10- Pure Perfection!.. When would you pick a switch over a bridge? When would you pick fiber over copper? When would you want to use ATM’s RSVP and QoS?