1. Chapter 14 Local Area Networks
Prof. Choong Seon HONG

2. Introduction
Three Generations of Ethernet

3. 14.1 Traditional Ethernet Physical Layer Physical Layer Implementation
Mac Sublayer
Physical Layer
Physical Layer Implementation
Bridged Ethernet
Switched Ethernet
Full-Duplex Ethernet

4. Designed to operate at 10 Mbps
Traditional Ethernet
Designed to operate at 10 Mbps
Access through CSMA/CD
Media shared between all stations

5. 802.3 MAC frame
Preamble – 7 bytes of alternating 0s and 1s to alert the receiver and allow it to synchronize
Start Frame Delimiter (SFD) – 1 byte – signals the beginning of a frame, last chance for synchronization – last 2 bits are 11
Destination address (DA) – 6 bytes – contains the physical address of the destination station or stations
Source address (SA) – 6 bytes – contains the physical address of the sender
Length/type – if less than 1518 then it defines the length of the data field – if more than 1536 then it defines the type of the PDU packet that is encapsulated
Data – data encapsulated from upper-layer protocols : 46 ~ 1500 bytes
CRC – CRC-32

6. Minimum and maximum length of a Frame

7. Addressing Ethernet addresses in hexadecimal notation
Each station on an Ethernet network has its own network interface card (NIC)
NIC provides the station with a 6-byte physical address

8. Unicast and Multicast and Broadcast Address
Source address is always unicast
Destination can be unicast, multicast, or broadcast
Unicast specifies one recipient
Multicast specifies multiple recipients
Broadcast sends to all stations on the network – destination address is forty-eight 1s

9. Physical Layer
Physical layer for 10-Mbps Ethernet

10. Physical Layer Signalling(PLS)
PLS sublayer encodes and decodes data
Using Manchester Encoding
Data rate of 10 Mbps

11. Attachment Unit Interface (AUI)
A Specification that defines the interface between the PLS and MAU.
Developed to create a kind of medium-independent interface interface.

12. Medium Attachment Unit (MAU)
MAU (transceiver) : transmitter and receiver
Transmitting signals over the medium; receiving signals over the medium; detecting collisions
Medium dependent
Transceiver is a transmitter and receiver, can be external or internal
Position and Functions
of a Transceiver

13. Medium Dependent Interface (MDI)
To connect the transceiver (internal, external) to medium, we need a MDI.
For an external transceiver, it can be a tap or a tee connector.
For an internal transceiver, it can be a jack.

14. Physical Layer Implementation
Categories of traditional Ethernet

15. 10Base5 : Thick Ethernet thick Ethernet or Thicknet
bus topology, external transceiver
Connection of a station to the medium using 10Base5

16. 10Base2 : Thin Ethernet
Connection if stations to the medium using 10Base2
Thin Ethernet or Cheapernet
bus topology, internal transceiver or a point-to-point connection via an external transceiver

17. 10Base-T : Twisted Pair Ethernet
physical star topology
stations connected to a hub with internal or external transceiver

18. 10Base-FL : Fiber Link Ethernet
uses star topology to connect stations to a hub
normally implemented with external transceiver having two pairs of fiber-optic cables connecting it to the hub

19. Bridged Ethernet
Raising the bandwidth
Separating collision domains

20. Sharing Bandwidth

21. Raising the Bandwidth A Network with and without a Bridge
10/6 Mbps vs 10/12 Mbps in case that traffic is not going through the bridge

22. Separating Collision Domains

23. Switched Ethernet
Bandwidth is shared only between the station and the switch (5 Mbps each)
N-port switch; Switched Ethernet

24. Full-Duplex Ethernet 10Base-T is always Full-duplex.
A Limitation of 10Base5 and 10Base2 half-duplex.
Evolution : switched Ethernet  full duplex Switched Ethenet
10Base-T is always Full-duplex.
Full duplex mode increases the capacity of each domain from 10 to 20 Mpbs.

25. Full-Duplex Ethernet
No need for CSMA/CD, this functionality can be turned off.
Each link is a point-to-point dedicated path between the station and the switch.
For flow and error control
Adding a sublayer called MAC Control between MAC sublayer and LLC sublayer

26. 14.2 Fast Ethernet
Evolution from 10 to 100 Mpbs doesn’t change the MAC sublayer.
Access method is CSMA/CD, which is kept for backward compatibility.
Frame format, minimum and maximum frame lengths, and addressing are the same.

27. Autonegotiation
Allowing two devices to negotiate the mode or data rate of operation.
To allow incompatible devices to connect to one another. For example, between 10 Mbps-device and 100 Mbps-device
To allow one device to have multiple capabilities
To allow a station to check a hub’s capabilities

28. Physical Layer

29. Reconciliation Replacing PLS sublayer in 10 Mbps Ethernet
But, encoding and decoding, which were performed by the PLS, are moved to the PHY sublayer (transceiver), because encoding in Fast Ethernet is medium-dependent.
Is responsible for passing of data in 4-bit format (nibble) to the MII.

30. MII The AUI is replaced with the medium-independent interface (MII)
Can be used with both a 10-and 100Mbps data rate
Features a parallel data (4 bit at a time) path between the PHY sublayer and the reconciliation sublayer

31. PHY (Transceiver) and MDI
Transceiver is responsible for encoding and decoding.
MDI is need to connect the transceiver to the medium.

32. Physical Layer Implementation

33. 100Base-TX Implementation
Uses two pairs of twisted-pair cable
Physical star topology
Internal or external transceiver
Transceiver – responsible for transmitting, receiving, detecting collisions, and encoding/decoding data

34. Encoding and decoding in 100Base-TX
Encoding/decoding – first performs block encoding using 4B/5B, then encoded using MLT-3 (multiline transmission, three level)

35. 100Base-T4 uses category 3 (voice-grade twisted pair) or higher UTP
uses 4 pairs
Encoding/Decoding – 8B/6T

36. Transmission Using Four Wires

37. Giga-bit Ethernet
No longer possible to keep the MAC sublayer untouched
Two distinctive approaches: half-duplex using CSMA/CD or full-duplex with no need for CSMA/CD

38. Physical Layer in Gigabit Ethenet

39. Physical Layer in Gigabit Ethenet
RS – reconciliation sublayer – sends 8-bit parallel data to the PHY sublayer via GMII interface
GMII – gigabit medium-independent interface) defines how reconciliation sublayer is to be connected to the PHY sublayer (transceiver)
does not exist outside the NIC
operates only at 1 Gbps
no connecter or cable
PHY (transceiver) – medium-dependent – encodes and decodes – can only be internal
MDI medium-dependent interface – connects transceiver to the medium – RJ-45 AND fiber-optic connectors

40. Gigabit Ethernet Implementation

41. 1000Base-X implementation
uses two fiber-optic cables
internal transceiver
encoding – 8B/10B then NRZ

42. Encoding in 1000Base-X

43. 1000Base-T implementation
designed to use category 5 UTP
four twisted pairs
encoding – 4D-PAM5 (4-dimensional, 5-level pulse amplitude modulation)

44. Encoding in 1000Base-T

45. Questions !