Computer Network Assignment Help

18-10-16 Rochio Varela 0 comment

TASK 1

Evaluate various LAN technologies available in the market. Describe the technologies in relation with scenario above.

Local area networks (LANs) is part of network which connects  two or more system or network OS device  that is called local area network (LANs)  such as floor of building or one building or one office in same floor or other floor of building and campus environment. LANs behave much like people when you have a meeting with three or more people: If you want to say something to someone in particular, you first say that person’s name or at least look at him. Or, if you want to tell everyone in the meeting something, you just say it because they can all hear you. Likewise, LANs are broadcast media—a term signifying that all devices on the media receive the same data. When you are cabling up your computers and networking devices, various types of topologies can be used. A topology defines how the devices are connected.

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Different type of LAN technologies

Ethernet IEEE 802.3 

Ethernet: – Ethernet is a physical medium that is directly connected to PC ethernet port of switch or networking device only one PC on a shared Ethernet segment can send a frame at one time, but all stations receive and look at the frame to determine if it is for them. the physical Ethernet specifications up to 100 Mbps. It provides scalability information that you can use when provisioning IEEE 802.3 networks. Of these specifications, 10BASE5 and 10BASE2 are no longer used but are included for completeness. Ethernet design rule is that the round-trip propagation delay in one collision domain must not exceed 512-bit times. This is a requirement for collision detection to work correctly. This rule means that the maximum round-trip delay for a 10-Mbps Ethernet network is 51.2 microseconds. The maximum round-trip delay for a 100-Mbps Ethernet network is only 5.12 microseconds because the bit time on a 100-Mbps internet server is 0.01 microseconds, as opposed to 0.1 microseconds on a 10-Mbps Ethernet network.

Ethernet is the underlying basis for the technologies most widely used in LANs. In the 1980s and early 1990s, most networks used 10-Mbps Ethernet, defined initially by Digital, Intel, and Xerox (DIX Ethernet Version II) and later by the IEEE 802.3 working group.

The following are specifications for Ethernet, each of which is described in the following sections:

  • 10BASE5
  • 10BASE2
  • 10BASE-T
  • 100BASE-T

Fast Ethernet (100-Mbps)

IEEE introduced the IEEE 802.3u-1995 standard to provide Ethernet speeds of 100 Mbps over UTP and fiber cabling. The 100BASE-T standard is similar to 10-Mbps Ethernet in that it uses carrier sense multiple access collision detect (CSMA/CD); runs on Category (CAT) 3, 4, and 5 UTP cable; and preserves the frame formats. Connectivity still uses hubs, repeaters, and bridges.100-Mbps Ethernet, or Fast Ethernet, topologies present some distinct constraints on the network design because of their speed. Ethernet network is 5.12 microseconds, as opposed to the more lenient 51.2 microseconds in a 10-Mbps Ethernet network. The following are specifications for Fast Ethernet, each of which is described in the following sections:

  • 100BASE-TX
  • 100BASE-T4
  • 100BASE-FX 
100BASE-TX Fast Ethernet

The 100BASE-TX description uses CAT 5 UTP wiring.  Fast Ethernet uses only two pairs of the four-pair UTP wiring. If CAT 5 cabling is already in place, upgrading to Fast Ethernet requires only a hub or switch and network interface card upgrades.

100BASE-T4 Fast Ethernet

The 100BASE-T4 specification was developed to support UTP wiring at the CAT  3, 4, or 5 . This specification takes advantage of higher-speed Ethernet without recabling to CAT 5 UTP. Fast Ethernet uses three pairs of four-pair UTP wiring

100BASE-FX Fast Ethernet
100BASE-FX Fast Ethernet is operates over two strands of multimode or single-mode fiber cabling and it can transmit over greater distances than copper media. It uses media interface connector (MIC), Stab and Twist (ST), or Stab and Click (SC) fiber connectors defined for FDDI and 10BASE-FX networks

Gigabit Ethernet IEEE 802.3ab

Gigabit Ethernet was first identified by two standards: IEEE 802.3z (Gigabit Ethernet) invented in year 1998 and second edition of IEEE 802.3ab in year 1999. The IEEE 802.3z for the operation of Gigabit Ethernet over fiber and IEEE 802.3ab coaxial cable and bring together the Gigabit Media-Independent Interface (GMII). These standards are superseded by the latest revision of all the 802.3 standards included in IEEE 802.3-2002.

Below is an overview of Gigabit Ethernet scalability constraints.

 Gigabit Ethernet Scalability Constraints
Type Speed Maximum Segment Length Encoding Media
1000BASE-T 1000 Mbps 100 m Five-level CAT 5 UTP
1000BASE-LX (long wavelength) 1000 Mbps 550 m 8B10B Single-mode/multimode fiber
1000BASE-SX (short wavelength) 1000 Mbps 62.5 micrometers: 220 m 50 micrometers: 500 m 8B10B Multimode fiber
1000BASE-CX 1000 Mbps 25 m 8B10B Shielded balanced copper

The following are the physical specifications for Gigabit Ethernet, each of which is described in the following sections:

  • 1000BASE-LX
  • 1000BASE-SX
  • 1000BASE-CX
  • 1000BASE-T

Wireless LAN

Wireless LAN (WLAN) applications include inside-building access, LAN extension, outside building-to-building communications, public access, and small office/home office (SOHO) communications. The first standard for wireless LANs is IEEE 802.11, approved by the IEEE in 1997. The current specification is IEEE 802.11-1999, with many amendments thereafter.

IEEE 802.11 implemented wireless LANs at speeds of 1 Mbps and 2 Mbps using Direct Sequence Spread Spectrum and Frequency Hopping Spread Spectrum  at the physical layer of the Open System Interconnection model. Direct Sequence Spread Spectrum divides data into separate sections; each section travels over different frequencies at the same time. Frequency Hopping Spread Spectrum uses a frequency-hopping sequence to send data in bursts. With Frequency Hopping Spread Spectrum , some data transmits at Frequency 1, and then the system hops to Frequency 2 to send more data, and so on, returning to transmit more data at Frequency 1.

1.2 What do you understand by quality of service (QoS) and bandwidth management? Evaluate and analyse with examples why do you think it is important to perform them

Quality of Service (QoS) 

Quality of service (QoS) configurations or outlines gives special treatment to positive traffic at the expense of others. This helps make your network performance more deterministic and predictable for this traffic.

QoS in the network addresses the following problems

The main reasons that can affect QoS are:

  • Latency
  • Jitter
  • Loss

Latency

In an IP network, latency is defined as the time taken for a packet to enter and leave the network. As shown in Figure  packet A enters the network at time = t0 and leaves the network at time = t1. The latency of the network, t2, for packet A, in this case, is t1 t0.

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Note that latency is an end-to-end measurement of network delay. The time, t2, is the total delay introduced from various components of the network. These include transmission technology used, the speed at which packets can be forwarded at each intermediate node, and the various transmission speeds along the way.

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Jitter

Jitter is affected by the traffic condition in the network. As a video packet traverses the network, it has to contend with packets from other applications along the way (for example, FTP and web applications). The latter two applications have a very different characteristic from that of the video: They are bursty by nature and may transmit variable-sized packets. The network needs to ensure that the jitter for the voice and video is not affected by these applications. This is when QoS is required.

Loss

Besides solving latency and jitter issues, preventing packet loss in applications such as voice and video is critical. Although losing one packet once every great while might not adversely effect             these applications, losing too many might produce undesirable results. A long silence might interrupt a conversation, or a video screen might appear blank. In the case of the bank doing surveillance using an IP camera, losing images might have serious consequences.

Packet loss also results from the traffic condition in the network. A converged network carries different application types of data, video, and voice. These different applications must contend for the resources in the network. If the network is congested, packets are dropped because no resources are available. The network must be able to prevent the loss of packets that belong to voice and video applications. This is an area QoS can help in mitigating the risk of packet loss.

1.3 Discusses LAN concerns and make recommendations to sustain network security, reliability and performance

Hierarchical Network Design: 

Hierarchical models are using layers to abridge the tasks for inter networking or network environment. Every layer can focus on explicit functions and allowing you to choose the right systems \ device and structures for each layer.

The profits of using hierarchical models for our network design mention below:

  • Cost savings in this models we can save the money or cost
  • Ease of understanding or we can understand very softly
  • Modular network progress
  • Improved error inaccessibility ,

When accepting hierarchical design models and several groups report cost savings because hierarchical design models are no longer trying to do everything in one routing or switching platform.

A traditional hierarchical LAN design has three layers:

  • The core layer provides fast transport between distribution switches within the enterprise campus.
  • The distribution layer provides policy-based connectivity.
  • The access layer provides workgroup and user access to the network.

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Core Layer

The core layer is backbone of switching in hierarchical design models in other word core layer is bran of network environment that is work on high-speed switching backbone that is vital to corporate communications. The core layer should have below mention characteristics:

  • Fast transport (speed is critical )
  • High reliability ( core layer is work as backbone of network  )
  • Redundancy (they should be fully redundant  )
  • Low latency and good manageability ( there is no latency in core layer )

Distribution Layer

The distribution layer is the segregation or isolation point between the network’s access layer and core layers. The distribution layer is used to implement below functions:

  • Policy for network traffic
  • QoS
  • Security filtering

Access Layer

The access layer provides user access to local system or PC on the network. The access layer is categorized by access switched and shared-bandwidth LAN sectors or segments in a hierarchical design models. Segmentation using LAN access switches provides high bandwidth to workgroups and reducing collision domains on Ethernet\ Fast or gigabyte segments. Functions of the access layer include the following:

  • Ethernet switching
  • more specific security
  • segmenting for more collision domains
  • connectivity to distribution layer via 100Mbps links
  • connect 10Mbps switches to workstations; 100Mbps switches to servers

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TASK 2

2.1 Design network infrastructure to fulfill the requirement of above scenario, including the diagram of the network infrastructure, and all devices (ie. Switches, routers, cables, etc.)

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In this above network design we have used following network resources

Router:-

Routers exchange information about destination networks using one of several routing protocols. Routers use routing protocols to build a list of destination networks and to identify the best routes to reach those destinations.

“Routing Protocol Selection Criteria,” discusses routing protocols in further detail. Routers translate data link protocols. They are the preferred method of forwarding packets between networks of differing media

As per our network design we are using six router, they are connected between each other throgh service provider network (ISP ) and all route are exchange between all location router . 

Switches: – Switches use specialized integrated circuits and switches can run in cut-through mode, where the switch does not wait for the entire frame to enter its buffer; instead, it begins to forward the frame as soon as it finishes reading the destination MAC address. Cut-through operation increases the probability that frames with errors are propagated on the network, because it forwards the frame before the entire frame is buffered and checked for errors, switches are exactly the same as bridges with respect to collision-domain and broadcast-domain characteristics. Each port on a switch is a separate collision domain. By default all ports in a switch are in the same broadcast domain. Assignment to different VLANs changes that behavior and we can create four VLAN in switch.

Customer Service VLAN – As per scenario 5 device or PC are required for this VLAN 

Accounts/Finance VLAN: – This department has 34 PC and a network printer and will have accessible to only those working in finance department 

Library VLAN :-  With 200 system , the library will be divided in two rooms with three  48 port switch  each of which will contain 100 devices including a network printer, They should also be able print to a network printer from these machines

2.2 Critically evaluate the suitability of network components in your design in terms of Security, Scalability and Availability

2.2.1 Security 

Dot.edu College  has a security policy in place, it can begin to apply the document and its rules to their particular environment. Dot.edu College  with truly comprehensive security policies find that what they have created is a roadmap that helps them implement the correct security appliances, mechanisms, and controls that satisfy their particular security needs. Dot.edu College will also quickly begin to find the weaknesses in their security posture through the process of identifying important resources and associated policies and tying that information to current inadequate security controls. This documentation is sure to change over time as the computing and physical environments change, which should be expected and accepted as normal security policy maintenance. . The underlying network security provides an perfect place to implement core and advanced security solutions. The center of these secure network solutions includes the Adaptive Security Appliances Integrated Services Routers (ISR), and Cisco Catalyst switches that have integrated security embedded in them. These are highly intelligent network security devices with many built-in security features that provide a framework for incorporating security throughout the network 

2.2.2 Scalability  

Scalability point of view network is setup in this manner so that we do  IOS upgradation of switch without any outage and downtime or other word it can refer to the ability of a system to increase its total output under an improved load when resources are added. For instance we are using UTP cat 3 cable and now we need to upgrade it to UTP cat 6 cable. 

2.2.3 Availability

Availability is signified as a percentage of time. How many days, hours, and minutes is the server  electrical infrastructure operational and supplying power over a given time period? Server  availability suffers whenever the electrical infrastructure fails to provide power to the room.

Most companies want extremely high availability for their server , because downtime affects their ability to be productive and perform business functions. How high, though, can vary significantly and is represented by the concept of nines. The more nines of availability, the closer to 100% uptime a system or device has reached. For example, that your company brings the DC electrical system offline for one hour of maintenance every month. Assuming there are no additional outages of any kind, that means that the DC is running for all but 12 of the 8760 hours in the year. That’s 99.863% of the time, or two nines of availability.

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REFERENCES

  • Carol, X, Computer‐mediated communication and social networking tools at work.Information Technology and People. 26 (2). PP.172 – 190.
  • Morten H. A.,2011, Sensemaking in Networks: Using Network Pictures to Understand Network Dynamics, in Roger Baxter, Arch G. Woodside (ed.) Interfirm Networks: Theory, Strategy, and Behavior.17. Emerald Group Publishing Limited. PP.1 – 197.

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