Designing the WAN Network

Arr company, based in Melbourne has its head offices located there on one building with different floors with different departments occupying different floors. Further, the company has offices in different geographical locations that are not more than 70 kms away from the head office for a total of six offices. This paper is a design solution that will enable all employees on the six different offices with most user requirements are met by servers located in their respective offices. However, the employees need to communicate with different offices to exchange files, use the intra net, and for for e-mail, therefore a wired network will be sufficient. This paper describes and details the design for a network that includes a local area network (LAN) and a wide area network (WAN) to meet the needs and requirements of the office; the design will be made in such a way as to keep the costs down, following the basic principles and rules of networking.

The company has six different offices within the Melbourne CBD and surrounding suburbs, with the maximum distance between any two offices being 70 kms. The concerns and issues to consider when designing the WAN include costs, latency, uptime, security (very important), lead time to increase the capacity on existing circuits and to implement new circuits, jitter, and packet loss. These concerns mainly relate to file transfers, sharing, and exchange between the different offices. The different branches will also need to communicate with each other using e-mail, and so require Internet connection with reliable up-times. The concerns with the Internet include uptime, security, latency, costs, packet loss, lead times for implementing new circuits and lead times for increasing the capacity of existing circuits; jitter is another concern [1]. With these concerns in mind, the proposed WAN network design will tackle these concerns while at the same time meeting the requirements of the users.

In order to ensure security and file integrity during file transfers, the WAN will be designed with a VPN (virtual private network) [2], based on the MPLS (multi protocol label switching) [3]. The MPLS VPN has been chosen as the default method for the WAN because it is a highly flexible way for routing several network traffic types and data transport, with the MPLS being the backbone. This will ensure high latency and security fr the network, as well as tackle jitter problems [4]. The MPLS type to be used is the pseudo wire (point to point) MPLS VPN that will use VLLs (virtual leased lines) to provide L2 (layer 2) point to point connections between the different office sites [5]. This type of MPLS has been chosen because it can have TDM, ethernet, and ATM frames encapsulated within them. Remote users will connect through the VPN IPSec protocol and will connect via remote dial up [6], such as workers on the move.

Designing the LAN Network

For the main office, there are three top floors in one building in the Melbourne CBD with three departments; marketing that has 20 work stations, general support with 32 work stations, and sales that has 38 workstations. The concerns for the head office, and indeed other offices, is security, costs, latency, and flexibility in the LAN network. To cater to the issue of costs, instead of physical LAN network connecting all the floors. The limitation of physical LANs is that scalability becomes a challenge, and adding physical devices such as switches work to increase costs, while costs is a major point of concern for Arr. The head office network will be a switched LAN that has VLANs; VLANs are implemented on the OSI model Layer 2 that offers reliable data transit across a physical link. The the data link layer is responsible for the network topology, physical addressing, error notification, line discipline, flow control, and ordered frame delivery. This layer is termed the link layer, subdivided into the LLC sub layer and the MAC sub layer [9]. Each floor ill have a physical switch, connected to computers using a 10 Mbps Ethernet cable on every floor.

The proposed LAN for the head office is a hybrid one with physical Ethernet (fast Ethernet or Gigabit Ethernet) with virtual LANs and switches to connect the different floors. A fast Ethernet cable with 100 Mbps speed will then be used to connect the switches on every floor to the main switch; using this approach and the WAN design, related users even in different physical locations can then be grouped into a single sub network for easy operation and file sharing. The design for the LAN and VLAN is shown in the figure below; from switch D the connects to the other switches in each floor, there is a connection to the router, that then connects to the WAN and Internet. To ensure security, a physical firewall will be placed between the switch D and the router (See Fig II), with additional protection given through isolation of networks based on user groups for the whole company. The computers in each floor will be configured with a virtual LAN to reduce cabling and hardware costs. Because there are different users, it is easy to separate and isolate the users based on their needs, so that general support, sales, and marketing so that every set of related users are grouped together, without any physical constraints [8]. A virtual LAN (VLAN) is made up of several end systems in network equipment (switches or routers) or hosts and all are members of a single logical broadcasting domain; by using a VLAN, the physical limitations of the broadcast domain are eliminated, hence ensuing uptime and speed, and reduces chances of network congestion (intranet) when there is exchange of large files, for example. The VLAN will be supported in the LAN switches and each VLAN will support a separate spanning tree. A single network infrastructure will be used as the VLAN backbone to create several multi layered or overlaid broadcast groups.

Conclusion

As for the head office, the proposed LAN network will be a star topology’ the star topology has been chosen because it is easy to add or remove users and extend the current circuit. Further the star topology ensures that the network remains resilient with a disruption in one connection not bale to affect the other users within the network; it is also a relatively easy network type to design and set up [7]. The main server supports the company’s intranet while there is a separate mail server to support the e-mail operations for the head office; given that the design for the LAN is a VLAN, the mail server can support users in other offices via the WAN. The proposed design has the advantages of solving some of the concerns that Arr faces, including security through the use of a VPN for the WAN and implementation of a physical firewall in addition to a software firewall in the main server at the head office. The network will be fast, with 10 Mbps for the various floors and related users and 100 Mbps fast Ethernet to connect the switches in every floor to the main switch, ensuring the network is always optimized, using virtualization will also solve the issue of the number of switches; general support and marketing have 32 and 38 workstations, which would require additional switches.

The diagram for the and design for the head office LAN located at Melbourne is shown in the figure II below; using the VLAN eliminates the need for a lot of cabling while enabling a fast and resilient Internet design both for the head office and other branches.

Conclusion

In providing a solution to the Arr company case study, a design proposal was given for a WAN and LAN, with details on the preferred cabling and topology for the LAN at the company’s main offices that occupy three floors. The company has three departments at its main offices that include marketing that has 20 work stations, general support with 32 work stations, and sales that has 38 workstations, and a total of six branches located within a 70 km radius, which all need to be linked with a high performance and low cost network solution.  The proposed solution for the WAN is an MPLS VPN with VPN IPSec for mobile access; this enhances security, ensures high performance, and at a minimal cost for its network of branches.  For the main offices, a VLAN built around a basic physical LAN is proposed, with virtual switches to meet the needs of all departments, using a star topology for the LAN built using Ethernet 10 Mbps cables for computer connections and 100 Mbps cables between switches in each floor and the main controller switch, connected to a mail and general server that connect with a router. The router provides connection to the WAN and the Internet

References

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