Advantages and Disadvantages of Ethernet

Keywords: ethernet advantages and disadvantages, disadvantage ethernet

A 10Base2, or thin Ethernet, network uses thin 3/16-inch coaxial cable (with 50-ohm) impedance for the network backbone. Thin coaxial cable is much easier to prepare and install than thick Ethernet cable which means transfer rate of 10 Megabits per second that uses baseband signaling, with a contiguous cable segment length of 100 meters and a maximum of 2 segments.

10Base5:

10Base5 uses thick coaxial cable. This version is the original Ethernet. It can operate at up to 10 Mbps and support cable segments of up to 500 meters which uses baseband signaling, with 5 continuous segments not exceeding 100 meters per segment. It is also known as thick Ethernet or ThickNet.

10Base-T:

10BaseT is a baseband 802.3-based Ethernet network that uses unshielded twisted-pair (UTP) cable and a star topology. This version can operate at up to 10 Mbps which uses baseband signaling and twisted pair cabling. It is also known as twisted-pair Ethernet or UTP Ethernet.

Features:

10BASE-T uses Manchester-encoding over two unshielded twisted-pair cables. The early implementations of 10BASE-T used Cat3 cabling. However, Cat5 or later cabling is typically used today.

10 Mbps Ethernet is considered to be classic Ethernet and uses a physical star topology. Ethernet 10BASE-T links could be up to 100 meters in length before requiring a hub or repeater.

10BASE-T uses two pairs of a four-pair cable and is terminated at each end with an 8-pin RJ-45 connector. The pair connected to pins 1 and 2 are used for transmitting and the pair connected to pins 3 and 6 are used for receiving. The figure shows the RJ45 pin out used with 10BASE-T Ethernet.

10BASE-T is generally not chosen for new LAN installations. However, there are still many 10BASE-T Ethernet networks in existence today. The replacement of hubs with switches in 10BASE-T networks has greatly increased the throughput available to these networks and has given Legacy Ethernet greater longevity. The 10BASE-T links connected to a switch can support either half-duplex or full-duplex operation.

Advantages:

Since each node on a 10 Base-T network has its own cable connecting it to a central hub, it is far less likely that any node can cause the entire network to fail. The hub also has a “partitioning” function built into it which allows it to detect a problem on any of its ports. If a problem is found, the node is disconnected from the rest of the network. This isolates the problem until the node can be troubleshot and repaired. Because of the partitioning function built in to the hubs and the star-wired topology, it is generally easy to troubleshoot a 10 Base-T network. In a worst-case scenario, one can be troubleshot by simply disconnecting nodes from the hub one at a time until the network recovers. Usually, the hub will give an indication as to which node is causing a problem, allowing the technician to troubleshoot that node as opposed to spending many hours finding where the problem is.

Disadvantages:

10 Base-T only allows distances from the hub to the node of 100 meters. In some installations, this can be a major problem if nodes need to be located farther away. The nature of UTP cable makes it considerably more sensitive to electrical noise than coaxial cable. Generally, this rules 10 Base-T out as an option for installations on factory floor environments or other locations with a high ambient noise level.

What are the different types of networking / internetworking devices? Explain the basic features of these devices.

Following are the networking / internetworking devices with their basic features.

Network Router:

A network device, typically connected to a range of LAN and WAN interfaces, that forwards packets based on their destination IP address. Routers receives an incoming frame, discards the data-link header and trailer, makes a forwarding decision based on the destination IP address, adds a new data-link header and trailer based on the outgoing interface, and forwards the new frame out the outgoing interface.

Network Repeater:

A repeater is a physical layer device. It receives, amplifies (regenerates) and retransmits signals in both directions. As far as the software is concerned, a series of cable segments connected by repeaters is not different from a single cable (except by some delay introduced by repeaters). A system may contain multiple cable segments and multiple repeaters. But no two transceivers may be more than 2.5 km apart and no path between any two transceivers may be traverse more than four repeaters.

Bridge:

A bridge is a data link layer device which is used to connect multiple LANs. It examines the data link layer addresses to do routing. Since they are not supposed to examine the payload field of the frames they route, they can transport IPV4, IPV6, Apple Talk, ATM, OSI or any other kinds of packets.

Gateway:

A gateway can translate information between different network data formats or network architectures. Suppose a computer using the connection-oriented TCP/IP protocol needs to talk to a computer using the connection-oriented ATM transport protocol. The gateway can copy the packets from one connection to the other, reformatting them as need be.

Switches:

Switches are similar to bridges in that both route on frame addresses. In fact, many people use the terms interchangeably. The main difference is that a switch is most often used to connect individual computers. As a consequence, when a computer wants to send a frame to another the bridge gets the frame but just discards it. But the switch must actively forward the frame to other because there is no other way for the frame to get there.

What is the range of addresses in the classes of internet addresses? Evaluate each class of logical addresses.

There are five IP address classes, following table show each class and the range of addresses.

Class

Beginning Address

Ending Address

A

0.0.0.0

127.255.255.255

B

128.0.0.0

191.255.255.255

C

192.0.0.0

223.255.255.255

D

224.0.0.0

239.255.255.255

E

240.0.0.0

255.255.255.255

In Class A through Class E. each is used with a different type of network. The address classes reflect the size of the network, and whether the packet is unicast or multicast. In the unicast method of transmission, one copy of each packet is sent to each target destination. If there are eight workstations designated to receive a packet, such as a portion of a video clip, then it is transmitted eight times. In the multicast method, the recipients are placed in a group, such a group of all eight workstations. Only one packet is sent to the group, via a router or switch, which then packet to each group members.

Class A is used for the largest networks composed of up to 16,777,216 nodes. Class A networks are identified by a value between 1 and 126 in the first position of the dotted decimal address. The network ID is the first 8 bits and the host ID is the last 24 bits.

Class B is for medium-sized network composed of up to 65,536 nodes and it is identified by the first octet of bits ranging from decimal 128 to 191. The first two octets are the network ID, and the last two are the host ID.

Class C addresses are used for network communication on small networks of 256 nodes or less. The first octet translates to a decimal value in the range of 192 to 223 and the network ID is contained in first 24 bits, while the host ID is contained in the last 8 bits.

Class D addresses do not reflect the network size, only that the communication is a multicast. Unlike Classes A through C, the four octets are used to specify a group of nodes to receive the multicast, which consists of those nodes that are multicast subscription members.

Class E is used for experimentation and address range from 240 to 239.255.255.255 in the first octet.

Task 2

What is Bandwidth? Explain the other factors for network communications.

Network bandwidth is the measure of the data carrying capacity of the network. When simultaneous communications are attempted across the network, the demand for network bandwidth can exceed its availability. The obvious fix for this situation is to increase the amount of available bandwidth. But, because of the previously stated constraints, this is not always possible.

In most cases, when the volume of packets is greater than what can be transported across the network, devices queue the packets in memory until resources become available to transmit them. Queuing packets causes delay. If the number of packets to be queued continues to increase, the memory queues fill up and packets are dropped.

The characteristics of the information being communicated also affect its management. For example, the delivery of a movie uses a relatively large amount of network resources when it is delivered continuously without interruption. Other types of service – e-mail, for example – are not nearly as demanding on the network. In one company, an administrator might decide to allocate the greatest share of the network resources to the movie, believing that this is the priority for his customers. This administrator may decide that the impact will be minimal if e-mail users have to wait a few additional seconds for their e-mail to arrive. In another company, the quality of a video stream is not as important as critical process control information that operates the manufacturing machinery.

What is Physical address and what is the difference between Physical address and Logical address? Explain it in detail.

The Physical address is specific on the local network and it represents the address of the end device on the physical media. In an Ethernet using LAN, this address is also called as Media Access Control address. On the local Ethernet network, when two end devices communicate, the frames that are exchanged between them contain the destination and source Media Access Control (MAC) addresses. It is in hexadecimal notation assigned by manufacturer. This address is much like postal address because it enables communication to be sent to specific destination.

Physical address is 48-bit address burned into the ROM of the NIC card which is a Layer 1 device of the OSI model. This is divided into 24-bit vendor code and 24-bit serial address. This is unique for each system and cannot be changed. While the logical address is a 32- bit address assigned to each system in a network. This works in Layer3 of OSI Model which is generally called IP address.

What is the difference between Layer 1, Layer 2 and Layer 3 devices? Describe it according to the Layer’s features.

OSI model have 7 layers which perform many different functions. Every layer has its own unique features and function and a device which help the layers to work properly.

Layer 1 is called Physical layer which consists of hardware, developed by engineers, in the form of electronic circuitry, media, and connectors. Therefore, it is appropriate that the standards governing this hardware are defined by the relevant electrical and communications engineering organizations.

By comparison, the protocols and operations of the upper OSI layers are performed by software and are designed by software engineers and computer scientists. As we saw in a previous chapter, the services and protocols in the TCP/IP suite are defined by the Internet Engineering Task Force (IETF) in RFCs.

Hardware components such as network adapters (NICs), interfaces and connectors, cable materials, and cable designs are all specified in standards associated with the Physical layer.

Layer 2 is called Data Link layer and its services and specifications are defined by multiple standards based on a variety of technologies and media to which the protocols are applied. Some of these standards integrate both Layer 2 and Layer 1 services.

A hub is an example of a layer 2 device. Switches are generally considered layer 2 devices, but many are capable of operating at layers 3, 4 or higher.

Router is the Layer 3 device. The role of the router is to select paths for and direct packets toward their destination. This process is known as routing. During the routing through an internetwork, the packet may traverse many intermediary devices. Each route that a packet takes to reach the next device is called a hop. As the packet is forwarded, its contents (the Transport layer PDU), remain intact until the destination host is reached.

Task 3

Explain 7 OSI layers briefly and define Router, Switch, and Bridge. Explain about encryption & decryption.

OSI Layers:

The Open Systems Interconnection (OSI) model was initially designed by the International Organization for Standardization (ISO) that provides a framework on which to build a suite of open systems protocols. The objective was that this set of protocols would be used to develop an independent international network that would not be dependent on proprietary systems.

Unfortunately, due to the rate at which it expanded, and the speed at which the TCP/IP based Internet was adopted, the OSI Protocol Suite development and acceptance lagged behind. Although few of the protocols, which are in widespread use today, are developed by using the OSI specifications, the major contribution has been made by the seven-layer OSI model in the development of other products and protocols for all types of new networks.

The OSI model provides an extensive list of functions and services as a reference model that can occur at each layer. It also depicts the interaction of each layer with the directly above and below layers.

No.

Layer Name

Description

Application

Performs services for the applications used by the end users.

Presentation

Perform data format information to the application. For example, the presentation layer tells the application layer whether there is encryption or whether it is s .jgp picture.

Session

Manages sessions between users. For example, the session layer will synchronize multiple web sessions and voice and video data in web conferences.

Transport

Defines data segments and numbers them at the source, transfers the data and reasonable the data at the destination.

Network

Creates and addresses packets for end-to-end delivery through intermediary devices in other networks.

Data Link

Creates and addresses frames for host-to-host delivery on the local LANs and between WAN devices.

Physical

Transmits binary data over media between devices. Physical layer protocols define media specifications.

Router:

A network device, connected to a range of WAN and LAN interfaces that sends packets according to their destination IP address. Routers acquires an incoming frame, puts away the data-link header and trailer, makes a forwarding decision based on the destination IP address, adds a new data-link header and trailer based on the outgoing interface, and forwards the new frame out the outgoing interface.

Switch:

Switches are similar to bridges in that both route on frame addresses. In fact, many people use the terms interchangeably. The main dissimilarity is that a switch is commonly used to connect one-on-one computers. As a consequence, when a computer wants to send a frame to another the bridge gets the frame but just discards it. But the switch must actively forward the frame to other because there is no other way for the frame to get there.

Bridge:

Encryption:

The process of obscuring information to make to unreadable without special knowledge, sometimes referred to as scrambling. The process takes the data to be encrypted and applies a mathematical formula to it along with a secret number (called an encryption key). The resulting value, which is called an encryption packet, is sent through a network.

Decryption:

It is the process of decoding data the back to its original form by giving that encryption key.

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