ETHERNET

Network Architecture Covers issue like how data will flow between the computers on the network. Involves with: Logical design Physical design

Introduction to Ethernet IEEE Ethernet is commonly used Local Area Network(LAN) technology developed by Xerox in 1970’s. Ethernet is a non-proprietary industry standard that is widely accepted by network hardware manufacturers. Characteristics: Flexible technology Can run on variety of network media Excellent bandwidth Reasonable cost of bandwidth

Ethernet Features

FeatureDescription Traditional topologyLinear bus Other topologiesStar bus Type of architectureBaseband Access methodCSMA/CD SpecificationIEEE802.3 Transfer speed10 Mbps / 100 Mbps Cable typeThicknet, Thinnet, UTP

Traditional Ethernet (10Mbps) Ethernet has been proven to be inexpensive, reasonably fast & very popular LAN technology. Among 10Mbps Ethernet technologies are: 10Base2 10Base5 10BaseT

10Base2 Ethernet 10Base2 = Thin coaxial cable / thinnet cable can be used to connect 4 computers without any hub or switch with both end of the cable terminated by a BNC terminator. It relies on CSMA/CD access method to regulate the traffic. The ethernet media is passive = means it requires no power source of its own & will not fail unless its physically cut / improperly terminated. Limitation: 185meters cable length only, with minimum 0.5 meters between each station allowing maximum 30 computers.

10Base2 Ethernet specification CategoryNotes Max segment length185 meters (607 feet) Connection to NICBNC T connector Trunk segments & repeaters5 segments can be joined using 4 repeaters Computers per segment30 computers per segment by specification Segment that can have computers 3 of the 5 segments can be populated Max total network length925 meters (3035 feet)

Thinnet rule 5 segments, 4 repeaters and 3 populated segments.

10Base5 Ethernet Also known as thicknet & has distance limit of 1640feet without repeaters. 10base5 topology uses an external transceiver to attach to the network interface card. NIC attaches to the external transceiver by an AUI cable to the DIX connector on the card. Some external transceivers clamp to the thicknet using vampire taps, others use BNC or N-series barrel connector.

10Base5 Ethernet

10Base5 cabling components

10BaseT Ethernet 1990’s IEEE introduced Ethernet using twisted pair (unshielded) cable known as 10BaseT. At the end of the cable there is RJ45 connector which resembles RJ11(for telephone) connector but bigger in size. The hub/switch of 10BaseT network serves as multi-port repeater & always located in wiring closet of building. Most are configured in star topology but internally they use bus signaling system. Max cable length is 100m, but repeaters can be used to extend the max cable length, with min length between computers is 2.5m allowing total 1024 computers to be connected using 10BaseT network.

10BaseT Ethernet

Specification of 10BaseT CategoryNotes CableCategory ConnectorsRJ45 at cable ends TransceiverEach computer needs one, some have it built in Transceiver to hub distance100m (328 feet) Backbones for hubCoaxial or fiber optic cable to connect to larger LAN Total no of computers per LAN without connecting components 1024 by specification

Ethernet cables Most current popular cable is CAT5, but CAT 5e cable supports Gigabit Ethernet. There are distance limitations to ethernet cables, after which transmissions will likely fail due to line noise, reduced signal strength etc. NameSegment length (max) Cable 10Base5500m/1640ftRG-8 / RG-11 coaxial 10Base2200m/606ftRG-58 A/U or RG-58 C/U coaxial 10BaseT100m/328ftCAT 3 or better unshielded twisted pair

Switched Ethernet Traditional ethernet are also known as shared Ethernet. It provides a fixed bandwidth which must be shared by all devices on the network within collision domain. More than 2 computers cannot send & receive data simultaneously due to the reason that they share a segment/hub/repeater. Hub/repeater doesn’t have ability to divide collision domain.

Switched Ethernet a switch/router can separate a network segment, making each segment working as independent of other segments. It makes the collision domain smaller & overall network becomes efficient. Switched Ethernet enables multiple nodes to simultaneously transmit & receive data over different logical network segments. It is much faster as fewer workstations must compete for the same time on media.

Switched Ethernet hub Switch Collision domain

Fast Ethernet Fast Ethernet is a improved version of traditional Ethernet operating at the speed of 100Mbps. Fast Ethernet are: 100BaseX 100VG-AnyLAN

100BaseX Ethernet Also called Fast Ethernet & runs on UTP category 5 cable & uses CSMA/CD is a star wired star topology. Similar to 10BaseT where all cables are attached to hub. A traditional LAN is half duplex but fast Ethernet is full duplex & can operate at 200Mbps theoretically. 100BaseX incorporates 3 media specifications: 100BaseT4 (4 pair Cat3,4 or 5 UTP) 100BaseTX (2 pair Cat 5 UTP or STP) 100BaseFX (2 strand fiber optic cable)

100BaseX Ethernet ValueRepresentsActual meaning 100Transmission speed 100Mbps BaseSignal typeBaseband T4Cable typeIndicates UTP cable using 4 telephone grade pairs. TXCable typeIndicates UTP cable using 2 data grade pairs FXCable typeIndicates fiber optic links using 2 strands of fiber optic cable.

100VG-AnyLAN Network VG (Voice Grade) AnyLAN combines the feature of both Ethernet & Token Ring architectures. Originally developed by Hewlett-Packard. Both 100BaseVG-AnyLAN & Fast Ethernet are about 5 to 10 times faster than traditional Ethernet & compatible with existing 10BaseT cabling systems. It allows easy & inexpensive upgrades from existing 10BaseT installations. Different names of 100VG-AnyLAN; 100BaseVG VG AnyLAN

Gigabit Ethernet (1Gbps) Latest version of Ethernet which offers a bandwidth of 1000Mbps but the performance is still being in compatible with existing Ethernets & uses the same CSMA/CD & MAC protocols. It can be used to aggregate traffic between clients & server farms & for connecting Fast Ethernet switches. Can also be used for high bandwidth applications such as medical imaging & CAD.

Ethernet Frame Format Data frame is also called a frame is an organized structure into which the data is placed for transmission across network. Data frames defines how data is organized (relative position, length of fields, placement of control information) In Ethernet data is sent in streams one bit at a time, data frame breaks the stream up into discrete chunks so that it can be managed. If there is an error in transmission, only the affected frames need to be resent.

Ethernet Frame Format Preamble 8 bytes Destination address 6 bytes Source address 6 bytes Type 2 bytes Data bytes CRC 4 bytes Original Ethernet Frame Max size = 1,582 bytes)