IEEE LAN STANDARD

IEEE LAN Standards

Institute of Electrical and Electronic Engineers (IEEE) has published a set of standards for LANs. The standards are collectively known as the IEEE 802.x standards. These standards have gained industry acceptance in the development and implementation of LANs.

The commonly used IEEE 802.x standards for LANs are:

1. IEEE 802.1
2. IEEE 802.2
3. IEEE 802.3
4. IEEE 802.4
5. IEEE 802.5

IEEE 802.1

The IEEE 802.1 LAN standard provides information about the prerequisites for the interface of LAN standards. This standard is also known as the Higher Layer Interface (HILI).
An interface is a set of services that a layer offers to the layer above it in the protocol suite.

IEEE 802.2

The IEEE 802.2 LAN standard is a part of the Logical Link Control (LLC) sublayer of the Data Link layer. LLC compensates for the difference between the various 802 networks by providing a single format and interface to the Network layer.

IEEE 802.3

The IEEE 802.3 LAN standard is used for 1-persistent Carrier Sense Multiple Access/ Collision Detection (CSMA/CD) LAN, which is commonly known as Ethernet. Using the CSMA protocol, a node transmits data packets when it finds the channel or the transmission media idle. Due to this, it is known as 1-persistent CSMA.

If the channel is free, the node transmits data; otherwise, the node waits for it to become idle. If there is a collision in the channel, all nodes terminate their transmission, wait for a random time, and retransmit the data.
The IEEE 802.3 LAN standard falls under the MAC sublayer of the Data Link layer and the OSI Physical layer.

IEEE 802.4

The IEEE 802.4 LAN standard, which is also known as the token bus, was developed to avoid collisions on a network.

The token bus comprises of nodes, which are physically arranged linearly but logically organized to form a ring. Each node on the ring knows the addresses of the nodes to its immediate left and right. The following figure shows a token bus.

Token Bus

The token bus is based on a principle of a calculated wait period for each node in the ring. If the token bus takes time t for each node to transmit a frame and there are y nodes in the ring, the wait period for each node would be at most t*y. Each node in the ring holds the token for an equal time, transmits its frames within that period, and then passes the token to its neighbor.

NB: A token is a special control frame required by a node to send the frames on the logical ring. A control frame carries the administrative information responsible for maintaining the ring or delivering data from the source to the destination.

IEEE 802.5

The IEEE 802.5 LAN standard is also known as the Token Ring. The standard defines the specification for ring networks.
When the ring is initially set up, all the nodes are idle and the token circulates in the ring. When a node needs to transmit data frames to the ring, it would need to acquire the token and remove it from the ring. There is only one token traversing the ring and only the token holder can transmit its frames to the ring.

   

NETWORK COMPONENTS OF A LAN

Network Components of a LAN

Any network requires four components so that the nodes within it can communicate with each other and exchange information. These components include the following:

1. The transmission medium over which the data is exchanged
2. Rules and standards or protocols that facilitate the communication on the network
3. Software components in the form of NOS and management applications
4. Hardware devices that make up the network

Transmission media and protocols have already been covered in the previous articless. This section consists of the hardware components that are used in a LAN. These components include the following devices:

• Media connectors
• Network Interface Cards
• Repeaters
• Hubs
• Bridges
• Switches

Media Connectors

Media connectors are devices that connect a node to the transmission medium. They correspond to the Physical layer of the OSI reference model.

The commonly used media connectors include the following:

• British Naval Connectors (BNCs): These connectors connect coaxial cables to the node. These connectors are commonly used to connect nodes in a bus topology.
• T-Connectors: These connectors connect a network card of a PC to a network through cables.
• RJ-45 connectors: These connectors connect a PC to the network socket in the wall.
• DB-9 connectors: These connectors are used with different interfaces, such as video interfaces.
• DB-25 connectors: These connectors are used in serial connections and parallel interfaces, such as printers.

Network Interface Cards

Network Interface Cards (NICs) are the internal components of nodes and connect each node to the network. NICs operate in the Data Link layer of the OSI model. As a result, they perform the functions corresponding to this layer. They supply the hardware or physical address to each node on the network.

Repeaters

The information traversing through the transmission media on a network is known as a signal. Each medium has a maximum range to carry data reliably. While traversing, the signal undergoes weakening, degradation, and distortion because the length of the network segment increases. As a result, the transmission media restricts the network segment's length.

This problem is overcome by the use of a hardware device known as repeaters. Repeaters amplify and regenerate the signal from one node to another on a network. As a result, repeaters allow you to extend the effective length of the transmission media. A repeater does not filter or interpret the signal. It only repeats or regenerates the signal. The repeaters operate at the Physical layer of the OSI reference model. If the distance between the segments to be connected is very large, multiple repeaters may be required.

The following figure shows the extension of a network segment between two floors of the same building and two different buildings using repeaters.

Network Setup Using Repeaters

Hubs

Hubs are the central point of connection on a network because they allow multiple nodes and devices to be attached to them at the same time. The point where a node or a network device is attached to the hub is referred to as a port.
Based on the number of ports, hubs can be 8-port, 10-port, 16-port, 24-port, and 32-port. Hubs with a higher port capacity are also available in the market.

The following figure shows a hub:

Network Setup Using Hub

Hubs are of the following types:

• Passive hubs: These hubs do not regenerate the signals that they receive. In addition, the signals are sent to all devices that are connected to them.
• Active hubs: These hubs are capable of signal regeneration. However, they also forward the signals that they receive to all the nodes attached to them.
• Intelligent hubs: Apart from signal regeneration, these hubs are capable of basic management-related activities, such as gathering statistics about network traffic and collisions. In addition, the signal that passes through the hub goes to the destination node and the other nodes do not receive the signal. As a result, these hubs actively participate in reducing network traffic.

Bridges

Bridges are devices to connect network segments to each other. Bridges not only extend a network, but also filter unnecessary traffic on the network.

In a large bus setup, network traffic is very high because the data packets are sent to all the nodes attached to the bus. As a result, excessive traffic is generated, which results in the low performance of the setup. The network device, bridge, is used to overcome this problem. The bridge operates on the MAC sublayer of the OSI Data Link layer.

The bridge between the two segments examines each packet for its destination information and forwards only those data packets that are specific to other segments instead of sending all the data packets. This helps reduce the network traffic between the two segments and the overall network traffic. The segregation of the network into segments and their connectivity by bridges enables the smooth functioning of the network in the event of a breakdown of a particular segment. The following figure shows the use of bridges to manage network traffic.

Network Setup Using Bridge

Bridges cannot join dissimilar network segments because it needs the physical address of the device to send the data packet. The physical address is the function of the Data Link layer that uses different protocols on each type of network.

Switches

Switches are intelligent network devices that provide universal connectivity. At the same time, switches make efficient use of network resources, especially transmission media and their bandwidth.

On receiving data packets, instead of forwarding the packets to all connected nodes or segments, switches forward the packets only to the node that is the intended recipient of the packets. As a result, switches prevent network bandwidth from being wasted.

Switches are capable of basic network management activities, such as gathering statistics about network traffic and collisions. In addition, switches can also perform advanced management activities, such as selecting the optimal path for signal delivery within a network. As a result, switches play an active role in bringing down the overall network traffic.
Switches can operate at the Data Link layer, the Network layer, or both. The switches that operate at both the Data Link layer and the Network layer are known as multilayer switches. The switches perform both the switching and routing function.

NB: Bandwidth is the range of frequencies that a signal, such as analog or digital, can occupy over a specific transmission medium. Bandwidth is measured in bits of data per second (bps) for a digital signal, while it is measured in kilohertz (kHz) for an analog signal.




   

DLC & NETBEUI PROTOCOLS SUITES

DLC Protocol Suite  

The Data Link Control (DLC) protocol communicates between personal computers and mainframes (IBM Hosts). The DLC protocol provides services to the Data Link layer of the OSI reference model. It provides reliable data transfer across each connection on a network. The DLC protocol also defines frames and maintains flow control on the network.

NetBEUI Protocol Suite

NetBEUI stands for NetBIOS Extended User Interface. This protocol extends the functionality of the NetBIOS protocol. The NetBIOS protocol enables the transmission of data within a network. NetBEUI supplements this functionality of NetBIOS by formalizing the format of frames transmitted across the network. NetBEUI is best suited for small LANs because it is a nonroutable protocol that cannot route data packets across LANs.

       

SNA PROTOCOL SUITE

SNA Protocol Suite

IBM invented Systems Network Architecture (SNA) in the 1970s. The SNA protocol suite consists of the following:


Document Interchange Architecture (DIA): This specification controls file services, such as the storage and retrieval of files and file transfers among heterogeneous systems.

SNA Distribution Services (SNADS): This service controls the distribution of documents and messages.

Distributed Data Management (DDM): This service coordinates the execution of file requests locally or on a server. When DDM receives file requests, it executes them locally, if required resources are available. However, if required resources are not available on the node on which the request originated, the execution takes place at the server end, which can support the requirements.

Advanced Program-to-Program Communication (APPC): This service allows peer-to-peer communication among clients.

Information Management Systems (IMS): This service provides information management capabilities by scheduling priority transactions.

Customer Information Control Systems (CICS): This service provides multitasking capabilities, security, storage management, transaction management, and restart capabilities.


Advanced Peer-to-Peer Networking (APPN): This specification facilitates peer-to-peer communication among SNA-based networks.

Network Control Program (NCP): This specification provides routing and gateway functionality on SNA-based networks.

Virtual Telecommunication Access Methods (VTAM): This specification works with the NCP protocol to control network resources. In addition, it provides domain support on SNA-based networks.

Synchronous Data Link Control (SDLC): This specification supports remote connections through leased or dial-up connections. It provides point-to-point, multipoint, half duplex, and full duplex transactions.
Token Ring: This is the LAN specification for IBM Token Ring networks.

      

APPLE TALK PROTOCOL SUITE

AppleTalk Protocol Suite

Apple Computer, Inc. developed the AppleTalk protocol suite in the early 1980s. This protocol suite allows the integration of Macintosh computers on a network. It also provides interconnectivity between Apple computers and other networking technologies, such as IBM mainframes and VAX computers.
The following figure shows the AppleTalk protocol suite mapped to the seven layers of the OSI reference model:

In the preceding figure, the AppleTalk protocol suite consists of the following protocols:


AppleShare: This protocol is subdivided into three applications, AppleShare File Server (AFS), AppleShare Print Server (APS), and AppleShare PC (APC). AFS allows users to interact with a file server while APS allows users to send print commands to the print server. APC provides interconnectivity with MS-DOS-based nodes.

AppleTalk Filing Protocol (AFP): This protocol facilitates file sharing between network nodes.

AppleTalk Data Stream Protocol (ADSP): This protocol provides the services of the Session layer of the OSI reference model.

Zone Information Protocol (ZIP): This protocol divides an internetwork into zones and coordinates the interaction of these zones. In addition, ZIP assigns service providers to zones.

Printer Access Protocols (PAP): This protocol establishes connections between network nodes and various servers, such as print and file.

AppleTalk Session Protocol (ASP): This protocol optimises file service functions.

AppleTalk Transaction Protocol (ATP): This protocol provides a reliable delivery service for connection-oriented operations.

Name Binding Protocol (NBP): This protocol maps the names of nodes to their addresses.


Routing Table Maintenance Protocol (RTMP): This protocol manages routing information.

Datagram Delivery Protocol (DDP): This protocol provides routing services.

AppleTalk Address Resolution Protocol (AARP): This protocol maps the physical addresses of devices to their logical addresses.

         

IPX/SPX PROTOCOL SUITE

IPX/SPX Protocol Suite

Novell Inc. developed this protocol suite in early 1980s. Although, officially this protocol is referred as the Netware protocol suite, but due to the immense popularity of two protocols, Internetwork Packet Exchange (IPX) and Sequential Packet Exchange (SPX), this protocol suite is commonly referred to as the IPX/SPX protocol suite.

The following figure shows the IPX/SPX protocol suite mapped to the seven layers of the OSI reference model:

In the preceding figure, the IPX/SPX protocol suite consists of the following protocols:


Service Advertisement Protocol (SAP): This protocol is used by various servers, such as file and print servers, to publicize their IPX addresses and services.
Netware Core Protocol (NCP): This protocol is used to make server functions, such as file and print sharing, available to clients.
Internetwork Packet Exchange (IPX): This protocol provides fast but connectionless communication service. For this purpose, it uses datagrams, which are not acknowledged. In addition to providing logical addressing on the network, IPX also provides routing services.
Sequential Packet Exchange (SPX): This protocol is connection-oriented and guarantees the error-free delivery of data packets.
Netware Link Service Protocol (NLSP): This protocol works with the IPX protocol to find the appropriate route between communicating networks.
Routing Information Protocol (RIP): This protocol provides routing-related information to the Network layer.
Link Support Layer (LSL): This protocol provides the interface between network cards and upper layer protocols.
Multiple Link Interface Driver (MLID): This protocol enables the integration of network cards with upper layer protocols.
       

NETWORK PROTOCOL SUITES: TCP/IP SUITE

Network Protocol Suites

A protocol suite is a hierarchical collection of protocols. Similar to individual protocols, protocol suites can either be developed by a standards organization or a vendor.
Some of the protocol suites are:

• TCP/IP protocol suite
• IPX/SPX protocol suite
• NetBEUI protocol suite
• AppleTalk protocol suite
• DLC protocol suite
• SNA protocol suite

TCP/IP Protocol Suite

Department of Defense (DOD) developed this protocol suite in collaboration with a number of research organizations and universities in the 1970s. Initially, this protocol suite was referred to as the Internet protocol suite because it evolved with the Internet. However, with the emergence of two of its protocols, TCP and IP, this suite is better known as the TCP/IP protocol suite.

The following figure shows the TCP/IP protocol suite mapped to the seven layers of the OSI reference model:

In the preceding figure, the TCP/IP protocol suite consists of the following protocols:


File Transfer Protocol (FTP): This protocol enables the transfer of files from one computer or node to another.
Telnet: This terminal emulation protocol enables access to remote nodes and works on the node as if you were working on it locally.
Simple Mail Transfer Protocol (SMTP): This protocol enables the exchange of electronic mails (e-mails) between two nodes.
Routing Information Protocol (RIP): This protocol provides routing-related information to the Network layer.
Open Shortest Path First (OSPF): This protocol helps the Network layer to discover the shortest available path across networks between two communicating nodes.
Transmission Control Protocol (TCP): This protocol enables reliable, connection-oriented data transfers between two nodes.

User Datagram Protocol (UDP): This protocol enables fast but unreliable connectionless data transfers between two nodes.
Internet Protocol (IP): This protocol moves data between the intermediate networks that lie between the source and destination nodes.
Domain Name Service (DNS): This protocol resolves the names of hosts to their corresponding logical addresses, known as IP addresses.
Internet Control Message Protocol (ICMP): This protocol generates control messages related to any error in connection or flow control.
Address Resolution Protocol (ARP): This protocol resolves the MAC address of a node given its logical address.

     

OSI LAYERS INTERACTIONS

OSI Layer Interactions

Various protocols are implemented at each of the seven layers defined in the OSI reference model. The protocols function based on the guidelines defined for each layer.
In the OSI model, a layer at one end of the communication can interact with a peer layer at the other end. The message travels down the layer of the sending end through the transmission medium to the peer layer of the receiving end.
The following figure shows the communication between the Transport layers of two peers:

Communication Between Transport Layers Of Two Peers

In case two peers need to communicate with each other, the Application layer initiates the message for the recipient end. However, the two Application layers cannot communicate directly. As a result, the message is passed to the Presentation layer at the sender end, which adds its own header to the message and passes it to the Session layer. The Session layer, in turn, adds its own header and passes it to the next lower layer, the Transport layer. In this manner, each layer at the sender end receives the message, adds its own header, and passes the message to the next lower layer. This is because the message is converted into bits and placed on the transmission medium at the Physical layer. The Physical layer does not append any header.
When the recipient's Physical layer receives the message, it passes the message to the Data Link layer. The header added by the peer Data Link layer is stripped and passed to the Network layer, which, in turn, strips its own header. In this manner, each time the message is passed to the upper layer, the corresponding header is stripped off. When the message reaches the Application layer, it is read and interpreted.
The following figure shows the communication between the layers of two communicating ends:

     

OPEN SYSTEM INTERCONNECTION REFERENCE MODEL

The Open System Interconnection (OSI)  Reference Model

The International Standards Organization Open System Interconnection (ISO OSI) reference model first achieved the International standardization of the protocols. ISO developed the standards for connecting systems that are open to communication with other systems.
The OSI reference model has seven layers. The following figure shows the seven-layer OSI reference model:

OSI Seven Layers

The seven layers of the model are listed as follows in the bottom-to-top approach:

• Physical Layer
• Data Link Layer
• Network Layer
• Transport Layer
• Session Layer
• Presentation Layer
• Application Layer

Physical Layer
The Physical layer is responsible for the transmission of data over a communication channel or the transmission medium. This transmission medium is the physical path over which the data is transmitted in the form of signals. During a transmission, the Physical layer converts the data into series of bits and places these bits on the transmission medium. This layer is also responsible for specifying the physical structure or topology of the network. Although the Physical layer deals with transmission media, the transmission medium is not specified.


Data Link Layer
The Data Link layer is responsible for the following aspects of communication:

1. Providing unique identification to each node on the network
2. Transforming data bits from the Physical layer into groups called frames
3. Detecting errors that occur during a transmission
4. Managing the flow of data packets or frames

The Data Link layer provides unique identity to each node on the network. It uses the network address, which is hard-coded into the network card of each node for this purpose. Although the Data Link layer is responsible for the detection of transmission errors, it is not responsible for the correction of errors.

The Data Link layer is divided into two sublayers. These are:

1. Media Access Control (MAC): This sublayer helps the nodes on a network to communicate with each other as it provides information about physical address of the node or the MAC address.
   
2. Logical Link Control (LLC): This sublayer establishes and manages a logical link between two communicating devices on the network. It provides error control and flow control within a network

Network Layer
The Network layer is responsible for the following functions:

1. Providing a unique network address to each node on the network
2. Transmitting data across networks
3. Controlling network traffic

The Network layer provides a unique address to each node on a network. The addresses are different from Data Link layer addresses because Data Link layer addresses can only be used for communication within a single local network. However, if a node on a network A, needs to communicate with a node on network B, it would not be able to do so using Data Link layer addresses.

For communication among different networks, a special Network layer-addressing scheme known as logical addressing is used. When two nodes that are located on two separate networks need to communicate with each other, they need the logical address provided by the Network layer.

The Network layer is also responsible for determining all the possible routes to the destination network and selecting the best path to the network where the destination node is located. This process is known as routing.


Transport Layer
The Transport layer is responsible for the following functions:

1. Organizing messages into segments or breaking large segments into smaller segments 
2. Delivering segments to recipients
3. Providing error control

The Transport layer segments and reassembles data. In case the upper layers generate large data packets, the Transport layer breaks the large packets into smaller segments that can be handled by lower layers. Similarly, when lower layers pass small segments to the Transport layer, it combines multiple segments to form large packets. Because the Transport layer deals with segmentation and reassembly, it is also responsible for correctly sequencing the segments so that the entire data can be reconstructed correctly.

The Transport layer is also responsible for the unreliable or reliable delivery of segments with the help of connectionless or connection-oriented services, respectively. The recipient acknowledges a transmission in connection-oriented services. If the sender does not receive an acknowledgement from the recipient within a specific interval, it retransmits the unacknowledged packets. In connectionless services, the sender continues to transmit packets without receiving acknowledgements.

The Transport layer also provides error control services. When a packet is lost during transmission, the Transport layer retransmits it after a specific interval. In addition, the Transport layer adds checksums to the segments before transmission. The recipients use these checksums to determine whether the segment was corrupted during the transmission or not. If the segment is corrupted, the Transport layer retransmits the appropriate segments.


Session Layer
The Session layer establishes, manages, and synchronizes the communication between two communicating nodes. The two nodes can exchange information only after a session has been established between them. In this case, session is defined as a logical connection between the two nodes.

The Session layer can also control the direction in which data flows. Based on this direction of data flow, a session can be any one of the following:

1. Simplex: Only one node can transmit data at a time.
2. Half duplex: One node can transmit while the other node can receive data. However, both nodes cannot transmit data at the same time.
3. Duplex: Both nodes can transmit as well as receive data at the same time.

Presentation Layer
The Presentation layer encodes and decodes data in a mutually agreeable format. As a result, this layer plays an important role in facilitating data exchange between heterogeneous hardware and software platforms that use different data formats. For example, if one node uses one byte to represent a character and the other node uses two bytes to represent a character, the Presentation layer plays a significant role in facilitating successful data exchange between the two nodes.

If required, the Presentation layer also compresses and decompresses data packets. As a result, the network traffic is less, preventing congestion. The Presentation layer also plays an important role in the encryption and decryption of data. This ensures high data security during transmission.


Application Layer
The Application layer provides an interface between the user and the network. It supports a number of software programs and end-user processes that act as a link between the user and the network. As a result, all network applications and protocols reside on this layer. This is the reason for the name Application layer. Some of the common applications and protocols that operate on this layer include e-mail, FTP, and Telnet.

      

COLLABORATIVE NETWORK COMPUTING MODEL

Network Computing Models

A network can be designed for processing information by either the client or the server. The network model can also be structured in a way that both the client and the server can process information. Depending on this flexibility, network computing models can be of three types:

Centralized network computing model

Distributed network computing model

Collaborative network computing model

Collaborative Network Computing Model

The collaborative network computing model is an advanced distributed computing model. In this model, nodes also share processing capabilities apart from sharing data, resources, and other services. In other words, processes can run on two or more computers. The following figure shows the collaborative network computing model:

Advantages
The advantage of the collaborative network computing model is:
Increased processing speed: The nodes on the collaborative network share the task of processing the request. This reduces the processing time and increases the overall network performance.
      

DISTRIBUTED NETWORK COMPUTING MODEL

Network Computing Models

A network can be designed for processing information by either the client or the server. The network model can also be structured in a way that both the client and the server can process information. Depending on this flexibility, network computing models can be of three types:

Centralized network computing model

Distributed network computing model

Collaborative network computing model

Distributed Network Computing Model

The distributed network computing model allows all network computers to take part in processing but at their respective ends, separately. This model allows sharing data and services but does not help the other network computers in processing.

In this network model, a processing-intensive task is broken into a subset of tasks and distributed among multiple nodes. The nodes work on their individual subsets of tasks. The following figure shows the distributed network computing model:

Advantages

Some of the advantages of the distributed network computing model are:

• Faster data access: The distributed network model allows a node to store the information locally. As a result, data can be accessed faster than in the centralized network model.
• High reliability: In the distributed network model, no single point of failure exists because the network does not entirely depend on a single node. This ensures lower network downtime.
• Customized network setup: The distributed network model offers the flexibility of treating different computers as clients and servers. It allows the optimized use of resources because the roles of the server and the client are interchangeable.

    

CENTRALIZED NETWORK COMPUTING MODELS

Network Computing Models

A network can be designed for processing information by either the client or the server. The network model can also be structured in a way that both the client and the server can process information. Depending on this flexibility, network computing models can be of three types:
Centralized network computing model
Distributed network computing model
Collaborative network computing model

Centralized Network Computing Model

In the centralized network computing model, the clients use the resources of high-capacity servers to process information. In this model, the clients are also referred to as dumb terminals with very low or no processing capability. The clients only connect to the server and not to each other. The following figure shows the centralized network computing model:

Advantages
Some of the advantages of the centralized network computing model are:

• Centralized data management: In a centralized network computing model, data is stored on the server. This increases the reliability of data because all data modifications are stored at a central location.
  
• High level of security: The centralized network computing model is a highly secure network model. This is because network security can be implemented and monitored centrally from the server.
  
• Cost effectiveness: High-end investment is required for establishing a high-capacity and secure server. On the other hand, clients require very low investment. This reduces the overall cost of setting up a centralized network.

Limitations
The centralized network computing model is a conventional model that is used only by a few network setups due to the following limitations:

• Low performance and network speed: The centralized network computing model consists of a server that manages numerous requests, simultaneously. This increases network traffic, consequently reducing the speed and performance of the network.
  
• Central point of failure: The server is the central place for storing data and processing all client requests. If the server fails, the functioning of the entire network is disrupted.

     

NETWORK TRANSMISSION MEDIA: Part2

Coaxial Cables

Coaxial cables commonly referred to as coax cables, derive their name from their structure. The structure is designed in a way that the two conductors share a common axis.
The following figure shows the structure of a coaxial cable.

In the preceding figure, the structure of the coaxial cable consists of a center conductor responsible for transmitting data. The outer conductor or shield protects this center conductor from EMI, ensuring that data transmission is not disrupted. The insulator provides a uniform space between the two conductors. A plastic jacket covers the cable and protects it from damage.

Coaxial cables provide effective protection against EMI during data transmission. This high level of resistance to EMI is attributed to the structure of the coaxial cable, which consists of a conductor made up of thick copper or stranded wire, which is covered with an insulator coating. An outer conductor made up of a braided metal shield covers this insulator coating.
The following are the most commonly used categories of coaxial cable:
RG-6
RG-8
RG-11
RG-58
RG-59


Coaxial cables are easy to install as compared to twisted pair cables, support higher transmission rates (10 Mbps and above). In addition, because coaxial cables suffer from lower attenuation rates than TP-based cables, coaxial cables effectively ranges up to 1 Km, which is a much higher range than either of the TP cables. Another advantage of coaxial cables is that although they use copper-based wire, they are less sensitive to EMI and other electrical interferences.

The main limitation of coaxial cables is that they are more expensive than TP cables. In addition, because of the hard covering of coaxial cables, the reconfiguration and reinstallation of the current network setup becomes difficult.

Fiber Optic Cables

Fiber optic cables are based on the fiber optic technology, which uses light rays or laser rays instead of electricity to transmit data. This makes fiber optic a suitable carrier of data in areas that are prone to high levels of EMI or for long-distance data transmissions, where electrical signals may be significantly distorted and degraded.

The components of a fiber optic cable include the light-conducting fiber, cladding, and insulator jacket. The cladding covers the core fiber and prevents the light from being reflected through the fiber and the insulating jacket. The outer covering (or the insulator jacket) is responsible for providing the required strength and support to the core fiber as well as for protecting the core fiber from breakage or high temperatures.
The following figure shows a cross-section of a fiber optic cable.

Fiber Optic Cable

Fiber optic cables can be differentiated into the following two categories:


Single mode cables: These cables use single mode fiber, which provides a single path for the light rays to pass through the cable, as shown in the following figure. A single mode fiber is suitable for carrying data over long distances.

Single Mode Cables

Multimode cables: These cables use multimode fiber, which provides multiple paths for light rays to pass through the cable. The following figure shows a multimode fiber:

Multimode Cable

Because light rays are unaffected by large distances or environment, the signals do not attenuate or suffer from EMI or other interferences. This makes multimode cables extremely safe and prevents outsiders from eavesdropping on an ongoing transmission. In addition, optical cables can support high bandwidths, from 100 Mbps to 2 Gbps. As a result, a network setup using fiber optic cabling can expand up to 10 Kms, without any problems. These facts have made fiber optic cabling popular on the networking market today.
Fiber optic cabling also has a few limitations. It is the most expensive cabling type. It is also cumbersome to install fiber optic networks because fibers are damaged if they are bent sharply.

Working of the Token Ring Network

Token Ring is a network architecture developed by International Business Machines (IBM). It is also a protocol, IEEE 802.5, developed by Institute of Electrical and Electronics Engineers (IEEE), which serves as a standard for IBM Token Ring.

When a token ring network is initiated, all the nodes on the network negotiate and decide upon the node that will monitor the network to ensure that the network traffic passes smoothly.

Data on the token ring network is transmitted in the form of tokens. The tokens are passed in a unidirectional way. When the destination node receives the message, it marks the message as “Read”. The message is passed in the ring and it comes back to the sender. The sender checks the message read mark to identify that the message was read by the destination node.

On the token ring network, only the node that possesses a token can transmit data. Each node on the network is allowed to hold the token for a specified time period. If the node holding the token does not have any data to transmit, it passes the token to the next node on the ring.


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