IST 201

1
IST 201

• Chapter 7

2
Repeater Classes

• Class I
• Between one Ethernet media and another of the
  same speed
• Any unlabeled repeater
• Class II
• Daisy-chaining is ok if cable length is less than
  5 meters.
• Repeaters cannot adapt between speeds.
• Bridges connect Ethernet segments of differing
  speeds.

3
Link Configuration

• Autonegotiate preferable
• Manual configuration is ok if autonegotiate fails.

4
1000 Mbps Ethernet

• 1000BaseT Twisted pair
• 1000Base-SX - short wave laser or LED on
  multimode
• 1000BaseLX long wave laser on single mode or
  multimode

5
1000-Mbps Parameters

• Bit time 1 nanoseconds
• Slot time 4096 bit-times
• Interframe spacing 96 bits
• Collision attempt limit 16
• Collision back-off limit 10
• Collision jam size 32 bits
• Max. frame size 1518 octets
• Min. frame size 512 bits/64 octets

6
Frame

• Same for all Ethernet.

7
Transmission

• Bits are sent faster
• Shorter duration
• Require more timing considerations
• Pushing bandwidth limits
• More susceptible to noise

8
Encoding

• Symbols used for data and controls
• Improves transmission of efficiency
• Improves synchronization
• Improves bandwidth efficiency
• Improves SNR characteristics

9
1000BaseT Encoding

• 8B1Q4

10
Line Encoding

• 4D-PAM5
• Cat5e or better
• Uses all 4 wire pairs in full duplex
  simultaneously
• Operates in permanent collision
• Send/receive on same pair
• Uses sophisticated hybrid circuits
• Uses a technique called echo cancellation
• Varied voltage levels
• Level 1 forward error correction (FEC)
• Careful cabling to standard prevents problems
  with
• Noise

11
Interoperability

• Gigabit Ethernet
• Fast Ethernet
• 10BaseT
• Bridge provides transfer from one speed to
  another
• Important for office desktop applications
• Wiring closets

12
Half Duplex 1000BaseT

• Works with CSMA/CD in half-duplex
• Not recommended

13
Timing

• Master clocking Mark time for
• Slave clocking transmissions
• Autonegotiate or manual configured for which
  device will act in which role.
• Usually a multiport device handles the master
  role when autonegotiate determines.

14
1000BaseSX LX

• Fiber
• Most recommended for backbones
• Group FastEthernet devices
• Good noise immunity
• No ground problems between floors/buildings
• New device options
• Excellent distance characteristics
• Not susceptible to dc drift (bias) that causes
  clocking errors (same digit represented
  sequentially)
• Not usually used for office desktop connections
• Copper 10/100/1000 network interfaces are common
• Copper is more user proof

15
Encoding

• 8B/10B

16
Line Encoding

• NRZ level driven not edge driven