Wired LANs Ethernet 13 1 Copyright The Mc

Wired LANs: Ethernet 13. 1 Copyright © The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display.

A Simple Network (LAN) 192. 168. 0. 10 Crossover UTP cable Internet 192. 168. 0. 1 140. 192. 40. 5 2

Typical LAN 9 th floor 2 nd floor 1 st floor Internet Data center 3

Campus Area Network (CAN) CDM Building De. Paul Center Administration Building Lewis Center 4

Metropolitan Area Network (MAN) Lake Forest Lincoln Park Rolling Meadow Loop Naperville 5

Wide Area Network (WAN) WAN 6

Success of Ethernet n n Easy to understand, implement, manage, and maintain Low-cost network implementations Extensive topological flexibility for network installation Interoperability and operation of standards -compliant products, regardless of manufacturer 7

LAN Services n n Users do not see the network, and they are interested in the services. What are the essential LAN services? n n n Printer sharing File sharing Application sharing Internet Surfing Intranet Web Database n n n Backup Fax Service Telephony Conferencing Management Miscellaneous 8

Network Components n n n Cables Network Interface Cards (NIC) Network hardware n n n n Hubs Switches Routers Gateways Printers Storage devices (NAS and SAN) Network Operating System (NOS) Software 9

Network Operating System Software programs that control resources shared over the network. Application Protocols Drivers Clients Network Server Example: Windows, Net. Ware, UNIX, Linux, Mac. OS 10

History of Ethernet Mc. Graw-Hill ©The Mc. Graw-Hill Companies, 11 Inc. , 2000

ALOHA Network (’ 68 -’ 72) Radio frequency w/ speed = 4. 8 -9. 6 K bps terminal IBM 360 Inventor: Norman Abramson Outbound channel: one-to-many transmission In-bound: same channel frequency with contention Slotted Aloha followed after Aloha. Throughput jumped from 18% to 37%. 12

First Ethernet at Xerox n n n Inventor: Bob Metcalfe Location: Xerox Palo Alto Research Lab Time: May 22, 1973, The first Local Area Network for personal computer (called ALTO) and printer (called EARS). Speed: 2. 94 Mbps Importance: carrier sense (listen first before transmitting) 13

Standardization of Ethernet n n n n Intel – Chip technology DEC – System engineering and hardware supplier Xerox – Ethernet technology 1980 - The Ethernet blue book (DIX) Speed – 10 Mbps 1981 – IEEE 802. 3 subcommittee 1983 – IEEE 10 Base 5 1989 – ISO 88023 14

Figure 13. 1 IEEE standard for LANs 13. 15

Figure 13. 2 HDLC frame compared with LLC and MAC frames 13. 16

Figure 13. 3 Ethernet evolution through four generations 13. 17

Figure 13. 4 802. 3 MAC frame 13. 18

Figure 13. 5 Minimum and maximum lengths 13. 19

Note Frame length: Minimum: 64 bytes (512 bits) Maximum: 1518 bytes (12, 144 bits) 13. 20

Figure 13. 6 Example of an Ethernet address in hexadecimal notation 13. 21

Figure 13. 7 Unicast and multicast addresses 13. 22

Note The least significant bit of the first byte defines the type of address. If the bit is 0, the address is unicast; otherwise, it is multicast. 13. 23

Note The broadcast destination address is a special case of the multicast address in which all bits are 1 s. 13. 24

Example 13. 1 Define the type of the following destination addresses: a. 4 A: 30: 10: 21: 10: 1 A b. 47: 20: 1 B: 2 E: 08: EE c. FF: FF: FF: FF Solution To find the type of the address, we need to look at the second hexadecimal digit from the left. If it is even, the address is unicast. If it is odd, the address is multicast. If all digits are F’s, the address is broadcast. Therefore, we have the following: a. This is a unicast address because A in binary is 1010. b. This is a multicast address because 7 in binary is 0111. c. This is a broadcast address because all digits are F’s. 13. 25

Example 13. 2 Show the address 47: 20: 1 B: 2 E: 08: EE is sent out on line. Solution The address is sent left-to-right, byte by byte; for each byte, it is sent right-to-left, bit by bit, as shown below: 13. 26

Figure 13. 8 Categories of Standard Ethernet 13. 27

Figure 13. 9 Encoding in a Standard Ethernet implementation 13. 28

Figure 13. 10 10 Base 5 implementation 13. 29

Figure 13. 11 10 Base 2 implementation 13. 30

Star. LAN (1 Base. T) n Problem with 10 Base 5 and 10 Base 2: poor cabling plant n n n What is the problem? Need: a cabling plant like telephone system 1983: AT&T and NCR, running Ethernet on UTP Speed: 1 M bps (This is the major issue) Importance: a market failure but a technology milestone n We have a structured cabling plant now 31

Star. LAN Ethernet hub or repeater • Network topology: now a star topology • A structured cabling plant similar to telephone network. Q: Why is star topology better than bus topology? 32

Figure 13. 12 10 Base-T implementation 13. 33

Ethernet Encoding Schemes n Manchester (10 Base. T) n n 0 -bit = + voltage, - voltage 1 -bit = - voltage, + voltage

Figure 13. 13 10 Base-F implementation 13. 35

NRZ-I Encoding (100 Base-FX) 0: no change 1: inverse

CSMA/CD Basic Algorithm n n n 13. 37 Medium idle? Transmit. Not ready? Wait until it becomes ready then wait interframe gap (9. 6 microseconds) or use p-persistent algorithm Collision detected? Continue transmission until min packet time reached (jam signal) Increment retransmission counter

CSMA/CD Procedure Station is ready to send Sense Channel try again channel busy Wait (backoff strategy) Send jam signal Transmit data and sense channel collision detected successful transmission 38

802. 3 Parameters (Table 3. 2) 39 Slot time 512 bit times (51. 2 s) Inter. Frame. Gap 96 bit times (9. 6 s) Attempt. Limit 16 (tries) Backoff. Limit 10 (exponent) Jam. Size 32 bits Max. Frame. Size 1518 bytes Min. Frame. Size 64 bytes Address. Size 48 bits (6 bytes)

Ethernet Performance Why do large frames have better performance? 40

CSMA/CD Basic Algorithm n n n 13. 41 Collisions are the killer!! Network throughput typically 20 -30%, 40% was max! Need a way to eliminate collisions What about token ring and token bus? What about bridges and switches?

CSMA/CD Collisions n n n 13. 42 How long does it take to hear a collision? Signals travel at 2/3 speed of light thru copper Propagation time = distance / velocity How many bits can you transmit during that time? Data transfer time = length of frame (bits) / data rate (bps)

Table 13. 1 Summary of Standard Ethernet implementations 13. 43

13 -3 CHANGES IN THE STANDARD The 10 -Mbps Standard Ethernet has gone through several changes before moving to the higher data rates. These changes actually opened the road to the evolution of the Ethernet to become compatible with other high-data-rate LANs. Topics discussed in this section: Bridged Ethernet Switched Ethernet Full-Duplex Ethernet 13. 44

Figure 13. 14 Sharing bandwidth 13. 45

Figure 13. 15 A network with and without a bridge 13. 46

Figure 13. 16 Collision domains in an unbridged network and a bridged network 13. 47

Figure 13. 17 Switched Ethernet 13. 48

How Switches Learn Host Addresses and Locations MAC forwarding table A 0260. 8 c 01. 1111 C 0260. 8 c 01. 2222 B E 0 E 1 E 2 E 3 0260. 8 c 01. 3333 D 0260. 8 c 01. 4444 • Initial MAC forwarding table is empty

How Switches Learn Host Addresses and Locations MAC forwarding table E 0: 0260. 8 c 01. 1111 A 0260. 8 c 01. 1111 C B E 0 E 1 E 2 E 3 0260. 8 c 01. 2222 0260. 8 c 01. 3333 D 0260. 8 c 01. 4444 • Station A sends a frame to Station C • Switch caches station A MAC address to port E 0 by learning the source address of data frames • The frame from station A to station C is flooded out to all ports except port E 0 (unknown unicasts are flooded)

How Switches Filter Frames MAC forwarding table A 0260. 8 c 01. 1111 C 0260. 8 c 01. 2222 n n E 0: E 2: E 1: E 3: 0260. 8 c 01. 1111 0260. 8 c 01. 2222 0260. 8 c 01. 3333 0260. 8 c 01. 4444 E 0 E 1 E 2 E 3 B 0260. 8 c 01. 3333 D 0260. 8 c 01. 4444 Station A sends a frame to station C Destination is known, frame is not flooded

Broadcast Frames A 0260. 8 c 01. 1111 C E 0: E 2: E 1: E 3: 0260. 8 c 01. 1111 0260. 8 c 01. 2222 0260. 8 c 01. 3333 0260. 8 c 01. 4444 E 0 E 1 E 2 E 3 0260. 8 c 01. 2222 B 0260. 8 c 01. 3333 D 0260. 8 c 01. 4444 • Station D sends a broadcast frame • Broadcast frames are flooded to all ports other than the originating port

MAC Forwarding Table n n n Unlike IP address, MAC address is local. MAC forwarding table is also local, within the single broadcast domain (which is an IP subnet). MAC address learning stops at the router, and a switch does not learn the MAC addresses at the other side of the router. n The switch learns one MAC address of the router.

Figure 13. 18 Full-duplex switched Ethernet 13. 54

5 -4 -3 Rule (10 Base. X) 5 segments, 4 repeaters, 3 populated segments hub/repeater 55

13 -4 FAST ETHERNET Fast Ethernet was designed to compete with LAN protocols such as FDDI or Fiber Channel. IEEE created Fast Ethernet under the name 802. 3 u. Fast Ethernet is backward-compatible with Standard Ethernet, but it can transmit data 10 times faster at a rate of 100 Mbps. Topics discussed in this section: MAC Sublayer Physical Layer 13. 56

Figure 13. 19 Fast Ethernet topology 13. 57

Figure 13. 20 Fast Ethernet implementations 13. 58

Figure 13. 21 Encoding for Fast Ethernet implementation 13. 59

MLT-3 Signal (100 Base-TX) three levels: +1, 0, -1 transition (at 1’s only): +1 => 0 = -1 => 0 => +1

Table 13. 2 Summary of Fast Ethernet implementations 13. 61

13 -5 GIGABIT ETHERNET The need for an even higher data rate resulted in the design of the Gigabit Ethernet protocol (1000 Mbps). The IEEE committee calls the standard 802. 3 z. Topics discussed in this section: MAC Sublayer Physical Layer Ten-Gigabit Ethernet 13. 62

Note In the full-duplex mode of Gigabit Ethernet, there is no collision; the maximum length of the cable is determined by the signal attenuation in the cable. 13. 63

Figure 13. 22 Topologies of Gigabit Ethernet 13. 64

Figure 13. 23 Gigabit Ethernet implementations 13. 65

Figure 13. 24 Encoding in Gigabit Ethernet implementations 13. 66

Table 13. 3 Summary of Gigabit Ethernet implementations 13. 67

1 G to 10 G (802. 3 ae)

10 Gb. E n n Full-duplex only (no CSMA/CD) Fiber only (802. 3 ae) WAN (SONET-friendly) PHY Mapping to OC-192 carrier n n n New line coding (64 b/66 b) Standard for copper 10 GBase-CX (802. 3 ak) - 2004 n n n Rate adaptation to SONET payload capacity dual coax cable <20 m (for data center use only) Standard for copper 10 GBase-T (802. 3 an) - 2006 n UTP cable (~50 m for Cat-6 and ~100 m for Cat-6 a)

IEEE P 802. 3 ba 100 G physical layer specifications for operation up to: n 40 km on single-mode fiber (SMF) using wavelength division multiplexing (WDM) n 10 km on SMF using WDM n 100 m on parallel OM 3 multimode fiber (MMF) n 10 m over a copper cable assembly 40 G physical layer specifications for operation up to: n 10 km on SMF using WDM n 100 m on parallel OM 3 MMF n 10 m over a copper cable assembly 70

Other High Speed LAN Technologies n n Token Ring Fiber Distributed Data Interface (FDDI) 100 VG-Any. LAN ATM LAN 71

Continuous Improvement n n n 10 M => 100 M (802. 3 u) => 1 G (802. 3 z and 802. 3 ab) 10 G (802. 3 ae, 802. 3 ak, 802. 3 an) Now 40 G and 100 G (approved in 2010) Virtual LAN (802. 1 Q) Quality of Service (802. 1 p) Fault tolerance n n n Spanning Tree Algorithm and Protocol 802. 1 D Rapid STP 802. 1 w and per VLAN STP 802. 1 s Link aggregation 802. 1 ad Port based network access control: 802. 1 X Wireless LAN: 802. 11 72

Power Over Ethernet (Po. E) Power over Ethernet (Po. E) Po. E delivers low-voltage power over Cat 5 cable. Ideal for applications such as wireless access points, access-card readers, IP telephones, IP video cameras, and may even be useful with cell phones, PDAs, and laptops. Once a proprietary technology, now it is an IEEE standard 802. 3 af. For small scale systems, installing Po. E may be as simple as installing a new line card in a switch or hub. 13. 73

Power Over Ethernet (Po. E) Power over Ethernet (Po. E) Installing Po. E in a large network may create physical power infrastructure problems. For example, each powered device (PD) can draw up to 15 watts from the switch/hub (power sourcing equipment, or PSE). If you have a 100 -port hub, that’s 1500 watts to support the PDs, plus another 1000 watts normally needed to drive the switch. The total is 2500 watts, or roughly 25 amps. Does your wiring closet have a 25 amp circuit? What if the switch has 300 ports? Po. E can deliver this 48 volt 15 watt power over the unused spare pair of wires in an Ethernet connection, or over the transmit/receive pairs. 13. 74