Ethernet%20Standards

1
Ethernet Standards

• Ethernet concepts origin
• DIX consortium 1979
• 10Mbps Ethernet 1st Blue book 1980
• IEEE group takes over Project 802
• 802.1 High Level Interface HLI
• Focused on high level inter-network protocols
  management
• 802.2 Logic Link Control
• 802.3 Data Link Medium Access Control
• DLMAC

2
Ethernet Standards

• 1982 DLMAC 3 groups
• 802.3 CSMA/CD driven by DIX
• 802.4 Token Bus burroughs, concorde,
• 802.5 Token Ring - IBM
• 1982 DIX IEEE merges
• 1st version of 802.3 Ethernet standard

3
Ethernet Standards

• IEEE 802.3 series of specifications for 10Mbps
• Thick coaxial thicknet 10Base5
• Thin coaxial thinnet- cheapernet 10Base2
• UTP XBaseT
• Fibre XBaseF
• Broadband version XBroad36

4
Ethernet Standards

• Other specifications
• 100 Mbs fast Ethernet
• 1000 Mbps gigabit Ethernet
• Switched Ethernet
• Proposal for 100MBps 1982
• IEEE 802 focused on 1- 20 MBps
• ANSI took up 100 Mbps - led to FDDI

5
Ethernet Popularity

• Low network management requirements
• Open standards
• Reasonable prices
• Easy to license
• 1990 10Mpbs Ethernet on UTP
• 10BASE-T inexpensive twisted pair
• Massive surge in Ethernet installations

6
Ethernet Popularity

• Coincides with distributed high-performance
  computing to the desktop
• Result
• Large networks many systems
• More network aware applications
• Massive increase in BW needs

7
Ethernet Popularity

• Result
• Need for higher bit rates fast Ethernet (1995
  100BaseT)
• Shift in Ethernet shared access to switched
  Ethernet
• High bit rate interconnectivity requirement
• Gigabit Ethernet 109 bits per second
• (Ethernet frame format maintained)

8
First Generation Ethernet 10Mbps
9
Network Connection

• Network Interface Card NIC
• Attachment Unit Interface AUI
• Medium Attachment Unit MAU
• PHY MAC HW
• LLC - SW

10
Network Connection

• PLS resides in DTE
• Data o/p
• Data I/p
• Carries Sense
• Error Sense
• MAC
• Data output in NRZ format

11
Network Connection

• MAC
• Data output in NRZ format
• PLS Manchester encoding differential
• AUI cable 3 different signal pairs
• DO
• DI
• CI (control input)

12
Network Connection

• AUI cable 3 different signal pairs
• Max length 50m
• 15 pin connectors
• Female on the DTE side
• Male on the MAU side

13
Network Connection

• MAU Transceiver
• Transmit data
• Receive data
• Loopback
• Collision detection
• SQE test
• Jabber protection

14
Bus Technologies

• 10BASE5 Thicknet coaxial
• 10BASE2 Thinnet, coaxial cheapernet
• 10BASE-T Twisted Pair

15
10BASE5 Thicknet

• Early 80s standard
• Tapped Bus topology 50 ohm coax cable
• Maximum 500 m segment length
• 100 users per segment
• Max 4 repeaters

16
10BASE5 Thicknet

• Transceivers separated by 2.5m
• AUI- NIC to transceiver max 50 m

17
10BASE5 Thicknet
18
10BASE2 Thinnet

• 1989 standard BNC ( British Navel Connector)
• Less expensive cable flexible to the desktop
• Max segment size 185m, max nodes 30
• Max length with repeaters 925 m
• Min distance between MAU 0.5m

19
10BASE-T Twisted Pair

• Uses standard voice grade telephone cable
• 1990 IEEE 802.3i UTP standard
• 4 twisted pairs
• Star topology logically bus
• Hub repeater at the centre
• Signal restoration
• Repeated incoming signal in all output ports

20
10BASE-T Twisted Pair

• Advantages of star
• Cable distance 100m to repeater
• MAUs can be connected via AUI
• MAU AUI can be part of DTE or repeater

21
10BASE-FL

• Runs over 2 strands of single/multimode fibre
• Fibre distance between MAU 2000m
• Point-to-point links

22
Functions of a NIC

• Create and Check CRC - error detection
• Physical Addressing
• Medium Access
• Framing - encapsulate decapsulate data
• Encoding Data
• Connection to Physical Medium
• Transceiver - translates signal to medium
  specific signal

23
Physical MAC addresses

• Unique Addresses
• assigned by the IEEE
• 48 bit address in two parts
• First 24 bits specify the vendor (block number)
• ex. AA-00-00 is a DEC NIC board
• ex. 08-20-00 is SUN
• Next 24 bits are a unique serial number

24
MAC addressing

• Static
• Most common
• Vendor guaranteed uniqueness
• Configurable
• SW assigned MAC address
• Dynamic
• Random pick and check for uniqueness

25
Types of addresses

• Broadcast
• Multicast
• Unicast

26
Broadcast addresses

• A MAC address of all ones
• All NICs on a network accept broadcast addressed
  messages

27
Multicast addresses

• A specific MAC address that only certain NIC are
  programmed to accept
• the first bit of the destination address is set
  to 1

28
Unicast addresses

• A unique MAC address assigned to each NIC which
  is used to send messages to that specific host.
• the first bit of the destination address is set
  to 0

29
Ethernet II Frame Format
30
Ethernet Operation

• Broadcast/half duplex network
• On a bus topology
• Listen first then transmit if clear
• What to do if you collide
• Backoff and try again

31
CSMA/CD

• LAN transmissions operate on the idea of a bit
  period
• For 10baseT this is 100ns (10,000,000 bits/sec)
• 3 times to keep track of
• Slot time
• Interframe gap
• Jam period

32
Timings

• Slot time min time transmitter needs to access
  media to transmit smallest frame
• All nodes must listen for 1 slot time before
  transmitting
• 512 bit periods or 51.2 µsec
• Interframe Gap (dead time) space between
  transmissions of 96 bit periods or 9.6 µsec

33
Timings

• On collision
• All stations involved stop transmitting and
  transmit 32 bit time (3.2 µsec) jam signal
• All attached stations hear the jam signal
• Back-off algorithm used to determine when another
  attempt will be made
• This is done up to 16 times

34
Ethernet Operations

• Min frame size 64 bytes (72 counting preamble
  and SFD)
• 64 bytes incl CRC, control, addresses and data
  fields (64 x 8 x 100ns 51.2 µsec)
• Max size is 1526 bytes