Network Management and Design: CSC81001 Assignment 2

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Unit code- CSC81001
Assignment 2
Network Management and Design Mode - Individual assignment
STUDENT NAME: KRISHNA MARRI
STUDENT ID:23320613
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Contents
PROTOCOL COMPARISON............................................................................................................................3
ROUTING APPROACH...........................................................................................................................3
PROTOCOL STRUCTURE.......................................................................................................................3
PERFORMANCE....................................................................................................................................4
ADVANTAGES AND DISADVANTAGES..................................................................................................4
APPLICATION.......................................................................................................................................5
NETWORK ARCHITECTURE ANALYSIS AND DESIGN.....................................................................................6
REFERENCES........................................................................................................................................9
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PROTOCOL COMPARISON
ROUTING APPROACH
The routing approach describes how each protocol learns routing information, selects the best path to
each destination network and maintains routing information. RIP is a dynamic distance vector routing
protocol that uses the Bellman-Ford algorithm to determine the best path. The best path to any
destination network is one with the least hop counts, with a maximum hop count of 15 hops. OSPF is a
link-state routing protocol that determines the best path using the Dijkstra's shortest path first
algorithm. The shortest path to a destination network is the least cost path based on a factor on the
bandwidth of the interface. The cost to the destination network is a cumulative value.
PROTOCOL STRUCTURE
RIP is a classful routing protocol but other versions of the protocol support classless routing (RIPv2 and
RIPng).A layer-3 device configured for routing information protocol RIP uses the multicast address
224.0.0.9 to discover other devices running the protocol. The discovery packets are sent to the UDP
destination port 520. The message sent by a configured device is a RIP request and the other device
responds with a RIP response message [1]. The response message contains the routing information
learned by the remote router. The administrative distance of a RIP route is 120, this value indicates the
trustworthiness of routing information when compared with information learned from other routing
protocols. RIP sends periodic updates every 30 seconds.
OSPF is a classless dynamic routing protocol that supports variable-length subnet mask. OSPF
implements a network using a hierarchical structure and areas to define the hierarchy, with area 0 being
the first area while other areas must connect to area 0 directly. The process of discovering other OPSF
devices begins with the exchange of link-state packets sent as hello messages to the address 224.0.0.5.
Other packet types are exchanged to build the adjacency between devices, share routing information
and maintain the routing protocol. Updates are triggered and the entire database is flushed after a
period of time. The protocol has a hello timer which defines the interval of discovery messages and is
also used to maintain adjacencies and the dead timer defines how long we can wait before declaring a
neighbour unavailable. OSPF supports different network types and can authenticate the adjacencies
between devices. OSPF has an administrative distance of 110 which is lower than RIP.
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PERFORMANCE
The performance of each protocol varies significantly with that of OSPF outweighing RIP. The first point
to consider is the convergence of each protocol. OSPF converges faster than RIP because the timers can
be modified to very low values. When the routing process is turned on, it takes a few seconds to
discover other devices and reach a stable state where each layer-3 devices has full information of the
network. The same applies to when a change occurs in the network, OSPF takes a few seconds to
discover and recover from a failure. RIP timers are on the high side because it takes 180seconds to
declare a device unavailable and 240s before information is removed from the routing table. OSPF
devices consume more CPU resources (processor and RAM) when running the algorithm and can impact
the device significantly as the network scales. RIP requires lesser CPU resources to run when compared
with OSPF.
ADVANTAGES AND DISADVANTAGES
The advantages and disadvantages of running either protocol are summarized below.
ADVANTAGES OF OSPF
1. Each OSPF layer-3 device builds its own topological view of the entire network.
2. Hierarchical design with multiple areas permits the topology to scale and support very large
networks.
3. The protocol converges very fast.
4. Updates are sent when there is a change in the network
DISADVANTAGES OF OSPF
1. The protocol is complex to design and implement.
2. High CPU and RAM usage required to run the link-state algorithm.
3. Requires high bandwidth link s for exchanging routing information.
ADVANTAGES OF RIP
1. The protocol is simple to design and implement.
2. Less bandwidth is required to exchange routing information
3. Low CPU and RAM is required to run the process on a device.
DISADVANTAGES OF RIP
1. A layer-3 device running RIP relies on information sent by directly connected devices to build
routing tables,
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2. The protocol uses a flat design which is limited to smaller topologies.
3. The protocol has a slow convergence time.
4. Updates are sent periodically
5. Susceptible to routing loops
APPLICATION
RIP has two versions with the original protocol designed for classful routing while RIP version 2 supports
classless routing. Both versions can only support smaller network topologies because of the limitations
associated with its convergence and loop prevention mechanism. OSPF is a highly scalable dynamic
routing protocol and can be implemented on very large topologies using multiple areas. The protocol
has a good loop prevention mechanism and can support different types of physical and logical network
topologies.
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NETWORK ARCHITECTURE ANALYSIS AND DESIGN
A review of the current network for DigiTour.com reveals that the topology is a redundant one with
multiple uplink paths towards building-A. The interconnection of the links between the buildings creates
a layer-2 loop in the network. A layer-2 loop occurs when there is an alternative path through which
traffic sent out of a port can return to the source Layer-2 device. This can significantly impact traffic
forwarding between network devices. To solve this issue, spanning tree can be configured between the
switch-links in the network. The layer-2 loop avoidance mechanism, spanning tree protocol blocks
redundant links and create a single path for traffic to flow towards an upstream device. The single path
in the network will be used to forward traffic while the redundant path would be blocked until there is a
failure of the active path. Although spanning tree can solve the challenges of layer-2 loops, it would be
insufficient to consider it as the ideal solution for the network.
A more severe challenge with the current topology is the absence of a hierarchy design. This makes
scaling the network a challenging feat. Modern network must adopt a hierarchical structure in order to
scale and support the growth of infrastructure with limited service disruption [1]. It supports the growth
of physical infrastructure, additional new services and growth of applications. A hierarchical network is
built with multiple layers of network infrastructure devices and different services at each layer of the
hierarchy. The use of different layers and blocks of devices permits the addition of new devices at any
layer of the hierarchy. Introducing a hierarchical design to the current topology will maintain the
redundancy and implement scalability. All devices in each building would be connected to them directly
to the switch in Building-A. This switch is the top of the hierarchy in the new network topology.
Based on the identified challenges with the current network an ideal proposed solution of hierarchical
design and the topological layout of the interconnectivity between the devices will be presented.
Furthermore, a new IP addressing plan for the network will implemented.
The current network uses 10.10.0.0/16 with the following subnets:
Building A: 10 PCs,
Building B: 20 PCs,
Building C: 50 PCs
Building D: 20 PCs
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Starting with the largest subnet, building C requires 50 addresses for each PC, the network has 16 host
bits available for borrowing.
Number of host bits for 50 hosts is 6 bits this leaves the network with 10 host bits, resulting in 1024 new
subnets. The new subnet mask is /26.
The first 4 new networks of the 1024 total subnets are:
10.10.0.192/26, 10.10.0.64/26, 10.10.0.0/26,10.10.0.128/26.
We assign the first subnet 10.10.0.0/26 to Building-C.
To solve for Building-B and Building-D both with 20 PC’s, 20 devices requires 5 host bits, using the
second subnet above: 10.10.0.64/26, we add 1 bit to the network port to obtain the new address:
10.10.0.64/27 and 10.10.0.96/27.
We assign 10.10.0.64/27 to Building-B and 10.10.0.96/27 to Building-C.
Next, we solve for Building-A using the address 10.10.0.192/26, Building-A requires 4 host bits for 10
PC’s, based on the address above we borrow 2 host bits to the network portion to create 4 new
networks;
10.10.0.176/28, 10.10.0.144/28, 10.10.0.160/28, 10.10.0.128/28
We assign the first network 10.10.0.128/28 to Building-A, the new topology is shown below.
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Figure 1 Network Diagram
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REFERENCES
[1] J. Doyle and J. Carroll, Routing TCP/IP, 1st ed. Indianapolis, Ind.: Cisco Press, 2006.
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