Ethernet Standards

• 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

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

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

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

Ethernet Popularity

• Result– Shift in Ethernet shared access – to switched

Ethernet– Subsequent – Fast Ethernet – 100BASE-T

(1995)– High bit rate interconnectivity requirement

• Gigabit Ethernet 109 bits per second

– (Ethernet frame format maintained)

Network Connection

• Network Interface Card – NIC

• Attachment Unit Interface – AUI

• Medium Attachment Unit – MAU

• PHY + MAC – HW

• LLC - SW

Network Connection

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

10BASE5 Thicknet

• Early 80s standard

• Tapped Bus topology – 50 ohm coax cable

• Maximum 500 m segment length

• 100/200 users per segment

• Max 4 repeaters

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

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

10BASE-FL

• Runs over 2 strands of single/multimode fibre

• Fibre distance between MAU – 2000m

• Point-to-point links

Functions of a NIC

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

signal

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

MAC addressing

• Methods– Static– Configurable– Dynamic

Types of addresses

• Broadcast

• Multicast

• Unicast

Ethernet Frame Format

FrameHeader

FrameData Area

8 6 6 2 46-1500 4

Preamble/ SYNCH

Dest. Address

Source Address

Frame Type CRC Data in Frame

Header

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

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