IST 201

1
IST 201

• Chapter 7

2
Legacy Ethernet

• 10Base5
• 10Base2
• 10BaseT
• Common Characteristics
• Timing parameters
• Frame format
• Transmission process
• Basic design rule

3
Parameters

• Bit time 100 nanoseconds
• Slot time 512 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

4
Ethernet Frame

• Must be between 64 1518 bytes
• Octets 7 1 6 6
  2 46-1500 4

S F D
Length Type
Preamble
Destination
Source
Data
FCS
5
Encoding

• Describes how bits are represented by voltages.

6
Manchester Encoding

• Used in 10 Mbps Ethernet
• Direction of the edge transition indicates
  whether it is a one or zero.
• Low to High transition 01 represents 1
• High to Low transition 10 represents 0
• Self-clocking each bit is transmitted over a
  predetermined time period

Called Biphase code
7
Shared Ethernet

• Share collision domain
• Multiple types of media can co-exist
• 10BaseT
• 10Base2
• 10Base5

8
Design Rule 5-4-3 Rule

• No more than 5 segments
• Separated by no more than 4 repeaters
• Coax no more than 3 segments can have hosts
• This rule prevents a 10 Mbps network from having
  propagation delay problems.

9
100 Mbps Ethernet (Fast Ethernet)

• 100BaseTx copper
• 100BaseFx fiber-multimode
• Common characteristics
• Timing parameters
• Frame format
• Parts of the transmission process

10
Timing Parameters 100 Mbps

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

11
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.

12
Link Configuration

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

13
1000 Mbps Ethernet

• 1000BaseT Twisted pair
• 1000Base-SX - short wave laser or LED on
  multimode
• 1000BaseLX long wave laser on single mode or
  multimode (recommended for Backbones)

14
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

15
Interoperability

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

16
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.

17
1000BaseSX LX

• Fiber
• Most often 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