The availability of high-speed network technology and individual computers capable of high-performance has increased the attractions in distributed computing . Due to the modern advancement of technology or company/organisation may outgrow their existing network system and they require an infrastructure update/upgrade .
Media Stream Infrastructure is embracing an upgrade to enhance its business and services through a modern digital converged network with QoS. Digital communication with its multiple branch office environments with voice, data, and video is the primary requirement of upgrade process including secure remote access for telecommuters to carry out daily business.
A properly designed network is a fundamental requirement for running a company day-to-day business. When designing a network careful consideration must be taken to include various elements such as business requirement, costs, no of users, devices, IP address plan, security policy, media, scalability, bandwidth and fault tolerance, etc.
Another key element of network designing process is topology, which influences costs, performance, and reliability. Network topology diagram shows where and how all the devices are interconnected in the network including redundant paths or aggregated ports between switches for resiliency in a LAN. Topology diagram also holds vital information for network troubleshooting and maintaining.
The main purpose of this report is to justify the decisions which were taken on the process of LAN, WAN designs and its other components. Section II explains about private and public IP address spaces and benefits of NAT. Section III discusses the preference of switches over hubs, media, and benefits of hierarchical LAN. Section IV compares the available WAN link options and solutions to connect HQ to branch offices and vice versa. Section V highlights security policy implementation and the role of security devices in the network. Section VI discusses effective options for secure remote access for the telecommuter. Finally, Section VII presents the essential costs for the whole Infrastructure update.
II. IP ADDRESSING SCHEME
When a datagram is transferring between one host to another host between HQ and branch offices, the datagram is routed by using the IP addresses as a source and destination.
Every device requires an IP address in the network to function or to be accessed and managed remotely. An IP address can be assigned to every end-devices statically or dynamically using DHCP server . When designing an IP address scheme, consideration must be taken for each device for present and future expansion. In a new proposed IP addressing scheme for Media Stream Infrastructure, several subnets are reserved for each site for possible future expansion shown in Annex A. The servers, printers and routers will be configured and assigned static IP address manually as it needs to remain fixed all the time. Other end-devices such as computers and VoIP phones will be assigned IP address dynamically by using DHCP server. This method will save time in the large network environments for IT/Network administrators from time-consuming manual IP address assignment.
An IP address is classified into Class A, B, C, D, and E, while Class A, B, and C are commonly used .
1. Private IP Address
Private IP addresses are designed to be used only within intranet and it is not advertised by routers to other routers outside the network . Main benefits of using private IP address space is to conserve globally unique IPv4 address space, and it provides increased flexibility to enterprises with a comparably large private address space at their disposal .
This enables Media Stream to design and manage its own IP addressing scheme according to its requirement.
The following three blocks: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 are reserved as private IP address by Internet Assigned Numbers Authority (IANA).
It is non-routable address, therefore, hosts using the private address as a source or a destination shouldn’t appear in the public Internet . However, it is possible for two private networks to communicate over a public network by using some method of encapsulation at their borders to public network keeping their private address private.
Network Address Translation (NAT)  makes it possible to communicate privately to public or vice versa by changing the private addresses space in the IPv4 packet header into a public address space . The main advantages of NAT are, enhanced security as a private address is not accessible from the public network and it provides access to the Internet .
Cisco Router 1921 has an embedded NAT feature which will be utilised by Media Stream to translate private to public address space and vice versa.
In Media Stream Infrastructure update, 192.168.0.0/23 is assigned to the whole infrastructure where 192.168.0.0/27, 192.168.0.160/27, 192.168.1.0/27, 192.168.1.96/27 is assigned to HQ Chester, Nice Branch, Antwerp Branch, and St. Gallen Branch respectively. Subnetting was carried out by using VSLM . A detailed IP addressing scheme can be found in Annex A.
3. Public IP Address
Any routable IP address over the Internet is considered as Public IP addresses. Company or organisation must have a block of pubic IP address assigned in order to be accessed from the Internet . Generally, Internet Service Providers (ISP) supply public IPv4 address as a part of services. They also provide other services such as email, website and Domain Name System (DNS) .
Media Stream will be provided public IP address by Virgin Media Business as a part of Leased Line WAN connection option. One of the drawbacks of Public IPv4 address is that it is running out of scope due to obdurate rapid growth in the Internet users.
...(download the rest of the essay above)