Exercise 4 – Virtual Private Network
1. Describe the IP Protocol:
IP Protocol is one of the protocols working in the Internet Layer of the OSI Model. Function of the protocol is to provide routing function across multiple networks. IP Protocol is implemented not only at the end systems but also at router where data is routed across different networks from source to destination (Stallings, 2005).
What is DNS:
DNS is Domain Name System. Individual machines/devices are connected to Internet via LAN switches/ routers or directly. Each of the devices/host machines connected to Internet must have a unique IP address in 32-bit numeric format for identification. IP address consists of two parts, network number and host number. Network number identifies the network on the internet whereas host number identifies a unique host on that network. However IP addresses in numeric format are hard to be memorized. The Domain Name System (DNS) is to translate the IP address of devices from human-readable hostnames to numeric addresses. Host/device are grouped together as domains and assigned with domain names. Domains are organized hierarchically. Each domain could have several subordinate domains as shown in the Domain Tree below (Stallings, 2005, p.88):-
The domain tree is subdivided into various levels with domain at the top level as the root domain. Each domain name consists of several parts such as http://www.google.com.hk representing their respective domain names at various levels. The most left part “hk” represent the name of the top-level domain. The “com” is the name of the subordinate domain at one level underneath the top-level domain “hk”. Similarly, “google” is the name of the subordinate domain at one level under “com” domain and two levels under “hk” domain. The above arrangement is for easy administration and identification.
Each node/level of the domain tree would have a name server and the corresponding name resolver program and distributed databases containing information such as IP addresses, name server for the domain etc. called the resource record (RR) (Stallings, 2005, p. 90). When a user enters a domain name into the browser, a request would be sent to the lowest level of domain tree for matching the corresponding IP address in numeric value for the required hostname. If matching cannot be located in the domain, such request would be passed to the next higher level for matching until a successful match is located. If no successful matching can be found, an error message would be prompted to the user. The DNS operation can be illustrated in the figure (Stallings, 2005, p.91) below:-
2. Describe TCP protocol: TCP is Transmission Control Protocol working at the Transport Layer of the OSI Model. Function of TCP protocol is to establish a reliable connection, in form of logical association, for the data transfer between applications. During the connection state, the connected entity would keep track of the data segments being transfer and would regulate the flow transfer and data recovery (Stallings, 2005).
TCP and IP Protocol works together to provide an reliable data transfer between applications. TCP establish connections and IP protocol deals with data transfer across networks. Due to the need for maintaining connection, the overhead associated with TCP would be higher compared with other less reliable protocol such as UDP protocol (Stallings, 2005).
3. Building e-business as an Intranet, Extranet, Web portal, B2B, B2C or Virtual Private Network?
Intranet: Intranet refers to the implementation of Internet Technology within an organization, rather than for global connectivity. Advantages of intranet as an e-business application include the follows:-
i) rapid prototyping;
ii) scale effectively;
iii) little training required because services and user interfaces are familiar to Internet;
iv) can be implemented on a variety of operation systems;
v) open architecture allowing interaction across platforms;
vi) supports a range of distributed servers;
vii) allows integration of legacy systems on client and server side;
viii) supports a range of media types; and
ix) inexpensive to implemented either in software and hardware.
Example of Intranet as e-business application: Water Supplies Department of HKSAR Government set up their intranet for access by all departmental staff for accessing records, news, bulletin boards, instructions, regional web pages etc. The link is as follows:-
http://intranet.wsd.gov/wsdmirror/en/html/info_publ/stat/index.htm (cannot access by external computer)
Extranet: Extranet extends the intranet concept to provide information and services to select outside populations, such as customers and suppliers. The essential features of extranets are to enable sharing of information between designated organizations.
Example of Extranet: Hennepin County Library’s extranet link at: http://www.hclib.org/extranet/ establish connections with various libraries for sharing the resources for their users.
Web portal: A web portal is a web sites containing large amount of information and links for accessing other web sites of the World Wide Web. Search engines such as Yahoo and Google are typical examples of web portals. Latest development of web portals is categorized into horizontal portals and vertical portals. Vertical portals are entrances to large amount of information and links related to a specific topic whereas horizontal portals cover topics of large extent. Portal owner makes profit by charging commission for referring links via the portal of advertising banners on the portal.
B2B – Business to Business: B2B exchange is a web site or collection of web sites providing a platform to facilitate business to business transaction more easily. Within the web sites, participated companies can procure products or services from each others to joining into alliances to tender for project bidding. Website Made-in-China with link http://www.made-in-china.com/ is a typical example of a B2B website dealing with various products made in China.
B2C – Business to Customer: Company websites to display and promote products for customers to purchase online. Usually the web sites would include full details of products, customer service support and electronic payment system to facilitate online payment. Examples of B2C web sites include HP’s website selling computer peripheral products, Nike’s web site selling Nike’s sports product and Tesco’s supermarket selling grocery products. These web sites would usually have delivery services as well.
4. Virtual Private Network: Virtual private network is to make up of public network to establish communications between different networks of an organization to act as a private network. However the configuration would expose the company traffic to eavesdropping and provides an entry point for hackers. Security measures would be provided by encryption and authentication packages or products. Alternatively, network manager might adopt IP Security (IPSec) to enhance the network security. University of Florida has installed a VPN under the link http://net-services.ufl.edu/provided_services/vpn/ to enable University Faculty, Staff, and Students to securely “tunnel” into campus over commodity networks.4. What role can a VPN play in business-to-business e-commerce?VPN can facilitate the setting up of business-to-business application between companies making use of public networks with minimum cost on the establishment of networks. The business-to-business application would become unjustified with high network establishment cost.
Reference
Incd, D. (2004). Developing distributed and e-commence applications. Addison Wesley.
Kurose, J.F. & Ross, K.W. 2005, Computer Networking: a top-down approach
featuring the internet (3rd edition). Boston: Pearson / Addison Wesley
Stallings, W. 2005, Business data communication (5th edition). Pearson Prentice Hall,.
Upper Saddle River, NJ.
