Ethernet Structured Wiring ITL

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman2 Transmission Media Guided Media –Twisted Pair –Coaxial Cable –Optical Fiber Unguided Media –“Broadcast”-type radio transmission Wireless LANs, Cell Phones, PCS –Satellite –Point-to-Point Microwave

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman3 Transmission Systems Basic multiplexing –DS-n (T1, DS3) –SONET (OC-3, OC-12, etc) –WDM Multiplexing and Other Functions –Ethernet –Frame Relay –ATM

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman4 Ethernet Designed as a broadcast medium; each transmission is received by every station Based on a bus architecture Manchester Encoding Several Media Types –10Base5 –10Base2 –10Base-T –10Base-F

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman5 10Base-T Simulates the Ethernet bus using an active star topology. Uses unshielded twisted pair wiring. “4-pair” (8 conductor) wiring is normally used, but only 2 pairs are used – 1 transmit pair one receive pair Each station connects to a central hub. –Cables are wired “straight through” –Hub ports are “crossed” (transmit/receive are reversed)

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman6 Fast Ethernet All use a star topology 100Base-TX –Two pair copper wire (Cat 5) –Same pin-out at 10Base-T, better wire 100Base-FX –Two fibers 100Base-T4 –Rarely used; 4 pair lower quality (cat 3) wires 1000Base-X (4 pair Cat 5 or 5E)

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman7 Ethernet Logic Ethernet is a CSMA/CD network – Carrier Sense Before sending a signal, listen to see if anyone else is transmitting –Multiple Access... because there can be many devices on the same wire trying to send –Collision Detection If, while transmitting a signal, you detect another signal Yours was “probably” lost You should “wait a while” and then send it again

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman8 Ethernet Frames To facilitate sharing, we bound the length of a message –Upper bound ensures that a single device can’t use the channel for too long bytes maximum –Lower bound helps make guarantees about collision detection 54 bytes minimum –These individual messages traveling on physical hardware are called “Frames” –Same term used for most network technologies

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman9 Frame Format Ethernet uses a fairly simple framing format –Initial pattern of bits referred to as a preamble 64 bits ( ) –Addressing information –The data we’re trying to send –Error detection data 32-byte “Cyclic Redundancy Check” (CRC) Also called FCS (Frame Check Sequence)

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman10 Ethernet Frame Types Type II SNAP “802.3 raw” from

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman11 Physical Address Each machine attached to a packet switch network is assigned a unique physical address –Sender must supply destination address when transmitting a packet –In most technologies, sender supplies source address as well Each technology defines its own address scheme –Ethernet in particular 48-bit address obtained when device is manufactured All 1s address reserved for broadcast One-half of the addresses reserved for multicast (a restricted form of broadcast); assigned by customer

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman12 Ethernet Hub aka Repeater Hardware device that connects two Ethernet cable segments and makes them appear to be a single cable –Repeats all packets from one cable to the other and vice versa –Performs the service one bit at a time –Introduces delay of 1 bit-time –Called “level 1” interconnect –Generalized to form a star rather than a bus –Can be very inexpensive, ≈ $20

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman13 Ethernet Bridge aka Switch Similar purpose as a repeater, but generally much smarter –Repeats at the packet level Introduces delay of 1 packet-time Does not forward collisions or noise –Does forward all broadcast packets –Adaptively “learns” source addresses and forwards only as needed –Called “level 2” interconnect –Can be very inexpensive, ≈ $40

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman14 Network Interface Cards Sends frames –Adds the preamble and CRC –Performs all of the collision detection and backoff Receives frames –Sees all frames on the wire Knows its address (often on ROM on the card May also answer to other addresses (multicast Only interrupts the CPU when a packet for the local computer arrive – Can generally be put in promiscuous mode Forwards all frames to the CPU –Useful for debugging/monitoring(/stealing)

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman15 Structured Wiring Main Cross-Connect (Main Distribution Frame) –Riser Cable(“Backbone”) Intermediate Cross-Connect (Int. Dist. Frame) –Horizontal Wiring Jack Field –Drop Cable Workstation

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman16 Why use Hierarchical Wiring? Flexibility = Lower Cost From Bates, Voice and Data Communications Handbook: –Estimated Cost for 50 single wire pulls: $15,568 –Estimated Cost for 50 dual wire pulls: $16,935

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman17 Wiring Standards Building Wiring Standards –Electronic Industries Association –Telecommunications Industry Association –EIA/TIA 568 Commercial Building Wiring Standard “Outside Plant” –Bell Labs technical publications –Now maintained by Telcordia (formerly Bellcore)

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman18 RJ-What? As an aside for the eternally curious: The RJxx nomenclature appears in the legal documents used by the FCC to identify permitted methods to connect telecom equipment to the network For the really, really curious: Title 47 CFR, Part 68, Subpart F, Section 502

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman19 Wiring Standards Level/CAT 11Mbps Level/ CAT 24Mbps Level/ CAT 316Mbps Level/ CAT 420Mbps Level/ CAT 5100Mbps 1000 Mbps (4 pair) 100m max distance Level/ CAT 5E100Mbps 1000 Mbps (4 pair) Level/ CAT MHzNot yet a standard

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman20 Applications Source: Lucent Technologies

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman21 FDDI 100 Mbps Ring Usually based on optical fiber Based on the Token Ring Standard Provides capacity pre-allocation Economics: –Ethernet is cheaper than token ring and does almost as good a job – so it wins –Fast Ethernet is cheaper than FDDI and does almost as good a job – so it wins

ITL: © Hans Kruse, Shawn Ostermann, Carl Bruggeman22 FDDI Details Ring: –Everything you send eventually comes back to you –A sender looks at the data coming back to ensure that it wasn’t “garbled” –Contention for the wire is handled by a circulating “token” –To send, a station waits for the token Grab the token Send your data Re-insert the token