This chapter describes the networking technologies and networking standards. It also examines various networking components such as repeater, hubs, bridges, switches, routers, gateways, CSU/DSU, Network Interface Card (NIC) and modems.
Ethernet is a Local Area Network (LAN) standard, which was designed by Digital Intel and Xerox (DIX). In an Ethernet network data sent by one station is received by another station. The data is passed to the upper layer for further processing with the help of frames. The frame header includes the destination address and the station whose destination address is included can only pick the frame and pass it further.
The LLC hides the fundamental differences in the physical network and provides a single interface to the next layer, which is the Network layer. It also acts as in interface between various network types such as Ring, Token and Ethernet and various network protocols such as Telnet, HTTP, TCP/IP and IPX.
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The older version was called IEEE 802.3 standard, version 1 and the newer version is called IEEE 802.3 standard, version 2. All the Ethernet LAN networks these days are based on IEEE 802.3 standard, version 2.
The MAC sub-layer and the physical layer are implemented using this standard. The variations of IEEE 802.3 standard, version 1 are 10Base2 and 10Base5 and variations of IEEE 802.3 standard, version 2 are the faster Ethernet such as Gigabit and 10Gigabit Ethernet.
2.1.1 Carrier Sense Multiple Access/Collision Detection (CSMA/CD)
CSMA/CD is an access method that describes accessing of wire and signals passing through Ethernet network.
Before sending data, a station in the CSMA/CD network checks if the network is busy or is it free. Station starts transmitting data only when the network is free. Sometimes, two stations might start sending simultaneous data after finding that the network is free and this is called collision. In case collision occurs, the backoff algorithm calculates the wait time and based on the wait time both the stations retransmit the data.
2.2 Ethernet Standards
Ethernet standards can again be classified as IEEE 802.2 and IEEE 802.3 standards. In this section, both these standards are explained in detail.
2.2.1 IEEE 802.2 Standards
Various 802.2 Standards are available. 10Base 2,10Base 5, 10BaseT (802.3i), 100BaseTX (Fast Ethernet, 802.3u), 10BaseFL (802.3j) and 100BaseFX (802.3u) standards are examined in this section.
10Base 2 standard is also called as Thinnet, this name is given based on the coaxial cable diameter that is uses. 10Base 2 offers a data transfer rates up to 10Mb/s, uses bus topology (Refer to Figure 2.1) and a 50-Ohm terminator is used to terminate both outer cable ends.
Figure 2.1: Bus Topology
The advantages of 10Base 2 are that it provides better protection against Electromagnetic Interference (EMI) and eavesdropping. Some features of 10Base 2 are as follows:
Type of cabling: Rigid
Maximum length:185 meters
Maximum nodes per segment:30
British Naval Connector (BNC) T connectors (Refer to Figure 2.2) are used to attach 10Base 2 stations.
Figure 2.2: BNC T Connector
10Base 5 standard is also called as Thicknet, this name is given based on the coaxial cable diameter that is uses. 10Base 5 uses bus topology, however, network nodes are attached to central cable in the bus using a different method.
Medium Attachment Unit (MAU), which is a transceiver (Refer to Figure 2.3a) attached the central cable is used to connect stations. Along with it AUI connectors (Refer to Figure 2.3b) are used to connect a cable, transceiver and the network interface.
Figure 2.3: (a) AUI connectors (b) MAU Transceiver
Some of the features of 100Base 5 are as follows:
Maximum data transfer rate: 10 Mb/s
Maximum length: 500 meters
Maximum length between a MAU and the AUI connector: 50 meter
Maximum number of nodes per segment: 100
10BaseT (802.3i) standard is also called as Ethernet. It denotes Ethernet against Cat 3, 4 and 5 UTP cabling and uses a star/hierarchical topology (Refer to Figure 2.4). Some of the features of 10BaseT (802.3i) are as follows:
Maximum data transfer rate: 10 Mb/s
Maximum cable length: 100 meters
Maximum number of attachments per segment: 2, a hub and a client
Figure 2.4: Star Topology
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It uses RJ-45 connectors (Refer to Figure 2.5) along with Cat 3, 4 and 5 Unshielded Twisted Pair (UTP). Sometimes, to employ cabling a transceiver is used with AUI interfaces of older network devices.
Figure: 2.5: RJ-45 Connectors
For attaching cable and RJ-45 connector a wire crimper tool (Refer to Figure 2.6a) is required. Also a punch down tool (Refer to Figure 2.6b) is essential to attach UTP cabling to a jacket.
Figure 2.6: (a) Wire Crimper (b) Punch Down Tool
100BaseTX (Fast Ethernet, 802.3u)
100BaseTX, Fast Ethernet, is similar to 10BaseT. The similarity with 10BaseT is that it uses of only four out of the eight wires in the cable. However, the cabling it requires is either Category 5 UTP or Category 1 Shielded Twisted Pair (STP). Some of its features are as follows:
Maximum data transfer rate: 100 Mb/s
Maximum cable segment distance: 100 meters
10BaseFL describes Ethernet against fiber optic cabling. It is the descendant of the Fiber Optic Inter-Repeater Link (FOIRL) specification, which permits a point-to-point link between two repeaters up to 1000 meters apart.
10BaseFL uses Multimode Fiber (MMF) optic cable. A MMF fiber optic cable is a relatively thick single strand of fiber core surrounded by a glass or plastic cladding, which is primarily used in LAN. The other cable available is Single Mode Fiber (SMF), which has a single strand of fiber and allows only one transmission mode. It is particularly apt for long-distance network, telephony and television broadcast systems.
10BaseFL is similar to 10BaseT. However, it operates over two strands of
MMF cabling. It uses one strand for sending and the other for collision detection and receiving. It can also work with existing FOIRL hardware and uses ST connector (Refer to Figure 2.7a) and SC connectors (Refer to Figure 2.7b). Some of its features are as follows:
Maximum cable segment: 2000 meters
Maximum data transfer rate: 10 Mb/s
Figure 2.7: (a) SC Connectors (b) ST Connectors
100BaseFX is similar to 100BaseTX that is it specifies operation over two strands of multimode fiber cabling. It operates in two modes namely half-duplex and full-duplex modes. Some of its features are as follows:
Maximum length in half-duplex mode: 400 meters
Maximum length in full-duplex mode: 2000 meters
Note: A few non-standard 100BaseFX based solutions permit distances up to 75 km for single-mode fiber optic cabling.
100BaseFX specifies SC to ST (Refer to Figure 2.8a) and MIC (Refer to Figure 2.8b) connectors. However, Mechanical Transfer Registered Jack (MT-RJ) (Refer to Figure 2.8c) connectors are also used in 100BaseFX-based product.
Figure 2.8: (a) SC to ST Connector (b) MIC Connector (c) MT-RJ Connector
MT-RJ connectors are a part of Small Form Factor (SFF) adapters. They are compressed in size compared SC and ST adapter types and increase the fiber density per rack unit in data closets.
2.2.2 IEEE 802.3 Standards
The 1000Base and 10Base Gigabit Ethernet standards are examined in this section. The major difference with the Ethernet standards discussed earlier is that it uses a different encoding type namely 8B/10B with simple Non Return to Zero (NRZ). The result is that 10 bits are sent instead of 8 and the maximum data transfer rate is 1 Gb/s with 20% overhead because of running 1250 MHz pulses.
1000Base Gigabit Ethernet Standards
Table 2.1 describes the 1000Base Gigabit Ethernet standards in detail.
It describes Gigabit Ethernet above CAT 5e UTP cable and transmission happens through all four pairs of cable wires. It supports maximum data transfer rate: 1000 Mb/s and maximum cable length of 100 meters.
Note: 1000BaseTX describes Gigabit Ethernet above CAT 6 UTP cable. However, it is not part of the IEEE 802.3 standard.
It covers two namely 1000BaseSX and 1000BaseLX Physical layer specifications for fiber optic media and one for shielded copper media namely 1000BaseCX.
It can make use of both multimode fiber and single mode fiber. Multimode supports a maximum of 550 meters length. Whereas, single mode fiber supports a maximum cable length of 5 km. It uses SC or the latest Local Connectors (LC) connectors.
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Note: LC connectors are half the size of SC connectors and are available in single and multi mode versions.
It uses multimode fiber with a maximum cable length up to 500 meters and IEEE standard specified SC connectors or LC connectors.
It is a special 150-Ohm secured coaxial cable, also called as Twinax and supports a maximum cable length of 25 meters. It has DB-9 connectors and is designed for short cable runs such as server-to-server connections.
Table 2.1: 1000Base Gigabit Ethernet Standards
10Base Gigabit Ethernet Standards
10Gigabit Ethernet standards are described by IEEE 802.3ae. It is also referred as 10GbE. It uses both multimode and single-mode fiber optics and the maximum cable length is enhanced up to 40 kilometers.
10 Gigabit Ethernet uses the same frame format and size as original Ethernet standard. However, CSMA/CD access method protocol is not required as it is a full-duplex and employs only fiber optic cabling. It uses encoding type 64B/66B, which are far more efficient and result in data transfer rate of 10.3 Gb/s.
The following are the three types of 10Base Gigabit Ethernet standards, which use SC or LC connectors:
10GBaseSR: It uses multimode fiber and supports maximum cable length up to 300 meters.
10GBaseLR: It uses single-mode fiber and supports maximum cable length up to 10 km.
10GBaseER: It uses single-mode fiber and supports maximum cable length up to 40 km.