Local Area Networks: Ethernet

IEEE Background Institution of Electrical and Electronic Engineering (IEEE) A professional non-profit organization Project group 802 under IEEE Entrusted with the task of setting standards relating to physical and logical links of nodes in a network Standard mostly applies to the Physical and Data Link layers Example IEEE standard for the Ethernet bus network

IEEE 802 Focus OSI Reference Data Link layer Physical layer Areas of applications Network cards and cables WAN connectivity etc. Different subgroups under 802 that focus on different activities of the LAN

IEEE 802 Subgroups and their Responsibilities Internetworking Logical Link Control (LLC) CSMA/CD Token Bus LAN

IEEE 802 Subgroups and their Responsibilities (Cont.) Token Ring LAN Metropolitan Area Network Broadband Technical Advisory Group Fiber-Optic Technical Advisory Group

IEEE 802 Subgroups and their Responsibilities (Cont.) Integrated Voice/Data Networks Network Security Wireless Networks Demand Priority Access LANs Ex: 100BaseVG-AnyLAN

A Perspective of IEEE 802 Standards in Network Communication Logical Link Control (LLC) Media Access Control (MAC) applies to both.

802 Layers - Physical Encoding/decoding Preamble generation/removal Bit transmission/reception Transmission medium and topology

Logical Link Control Flow control, Error control,& part of the framing Transmission of link level PDUs between two stations Must support multiaccess, shared medium Relieved of some link access details by MAC layer LLC defines PDU similar to HDLC Addressing involves specifying source and destination LLC users Referred to as service access points (SAP) Typically higher level protocol

Three generations of Ethernet

802.3 MAC frame Preamble: Provides an alert & a timing pulse SFD: Signals the beginning of the frame,& also warns the stations that this is the last the chance for synchronization. Last 2 bits alerts the receiver that next field is the destination address DA & SA : Physical address of receiver & sender Length or type: Define the upper layer protocol using the MAC frame IEEE use as length field to define the number of bytes in the data field

Minimum and maximum length If 18 bytes of header and trailer(6 SA + 6 DA + 2 Length + 4 CRC) Then Minimum length of data from the upper layer is 64-18= 46 bytes If the upper-layer packet is less than 46 bytes, padding is added to make up the difference

Ethernet addresses in hexadecimal notation

Unicast and multicast addresses Source address is always a unicast address Destination address can be unicast, multicast,or broadcast LSB of the 1 st byte defines the type of address Broadcast DA is a special case of the multicast address in which all bits are 1s

Access method: standard ethernet uses 1- persistent CSMA/CD SLOT TIME: round trip time + time required to send the jam sequence Defined in bits,time required to send 512 bits Depends on the data rate For 10-Mbps ethernet it is 51.2 μs

Physical layer

PLS

Manchester encoding

Categories of traditional Ethernet 10Base5,thick Ethernet, thicknet, Max length 500 m (coaxial cable) 10 base2,Thin coaxial cable,185 m, bus topology 10base-T,twisted pair Ethernet, physical star topology,100 m max length 10base-F,fiber,2000m,star topology

Connection of a station to the medium using 10Base5

Connection of stations to the medium using 10Base2

Connection of stations to the medium using 10Base-T

Connection of stations to the medium using 10Base-FL

Sharing bandwidth

A network with and without a bridge

Collision domains in a nonbridged and bridged network

Switched Ethernet

Full-duplex switched Ethernet

Fast Ethernet MAC Sublayer Physical Layer Physical Layer Implementation IEEE 802.3u

Fast Ethernet physical layer

Goal of Fast Ethernet Upgrade the data rate to 100 Mbps Compatible with standard Ethernet Same 48-bit address Same frame format Same Min & Max frame lenths

MAC sublayer For full-duplex no need of CSMA/CD Autonegotiation - Allows station or a hub a range of capabilities - Allow to negotiate the mode or data rate of operation

MII

Fast Ethernet implementations

100Base-TX implementation

Encoding and decoding in 100Base-TX Four Binary/Five binary coding scheme Multiline Transmission(three levels) Use 2 pairs of twisted pair cable Use MLT-3,as it has good bandwidth performance

MLT-3 signal

100Base-FX implementation 2 pair fiber cable, 100 m,4B/5B block coding,NRZ-I line coding

Encoding and decoding in 100Base-FX

100Base-T4 implementation Cat 4 UTP,4 pair of wires,100 Mbps * Data elements are encoded as six signal elements

Using four wires in 100Base-T4

Gigabit Ethernet MAC Sublayer Physical Layer Physical Layer Implementation

Physical layer in Gigabit Ethernet

Three Methods for Gigabit ethernet Traditional: 512 bits,length of bit is 1/100 shorter,slot time=.512microsec Carrier extension: Min length of a frame is 512 bytes Frame bursting:

Gigabit Ethernet implementations 2 wire Short,longwave(sx,Lx), STP CX,NRZ line encoding 4 wire use Twiste pair category 5 4D-PAMS line encoding Block coding is 8B/10B

1000Base-X implementation

Encoding in 1000Base-X

1000Base-T implementation

Encoding in 1000Base-T

Ethernet Protocol Standards 10 Mbps IEEE Mbps IEEE 802.3u 1 Gbps IEEE 802.3ab Uses all 4 pairs of the RJ-45 cable ( ) 10 Gbps IEEE 820.3ae