Tutorial 1

Tutorial 1

1. Write a post discussing the following : -

(i) Hypertext Transfer Protocol (Http) and Hypertext Transfer Protocol Secure (Https)

The Hypertext Transfer Protocol (HTTP) is an application protocol for distributed, collaborative, hypermedia information systems.HTTP is the foundation of data communication for the World Wide Web.

Hypertext is structured text that uses logical links (hyperlinks) between nodes containing text. HTTP is the protocol to exchange or transfer hypertext.

HTTP concepts include (as the Hypertext part of the name implies) the idea that files can contain references to other files whose selection will elicit additional transfer requests. Any Web server machine contains, in addition to the Web page files it can serve, an HTTP daemon, a program that is designed to wait for HTTP requests and handle them when they arrive. Your Web browser is an HTTP client, sending requests to server machines. When the browser user enters file requests by either "opening" a Web file (typing in a Uniform Resource Locator or URL) or clicking on a hypertext link, the browser builds an HTTP request and sends it to the Internet Protocol address (IP address) indicated by the URL. The HTTP daemon in the destination server machine receives the request and sends back the requested file or files associated with the request. (A Web page often consists of more than one file.)

The latest version of HTTP is HTTP 1.1.

The term HTTPS is an acronym for hypertext transfer protocol secure. The acronym precedes the URL in a website address. Few people are aware of its meaning. While HTTPS is almost an exact copy of the normal hypertext transfer protocol, this version of it is different because the “S” at the end identifies it as having a secure HTTP connection. A HTTPS connection is used frequently in businesses where sensitive information, such as social security numbers and credit card numbers, are being passed along at point of purchase sites or bill pay sites. The hypertext transfer protocol secure gives assurance that hackers are not able to intercept the message containing sensitive data as it heads to the server.

To understand the HTTPS protocol, it is important to understand that HTTPS is not a separate protocol from HTTP. It is simply a secure variation. Sending messages via an encrypted Secure Sockets Layer (SSL) or Transport Layer Security (TLS) connection gives users a reasonable amount of protection from eavesdroppers and intermediary attacks that can siphon important information or gain access to particular private servers. The HTTPS URL may specify a TCP port, but if it does not, most HTTPS connections use port 443 while regular HTTP use port 80. To prepare a server for HTTPS commands, the server must have a public key certificate issued for verification of the entity. Organizations may run their own version of certificate authority, to be doubly sure before sending HTTPS commands, especially with very sensitive information. It is then that HTTPS command is sent, so that there is no question as to who is receiving the information.

While HTTPS commands are a good idea for secure transfers, there are also certainly limits to what HTTPS can do. The level of protection that a HTTPS provides is dependent upon correctness of implementation by the web browser, the server software, and the cryptographic algorithms that are supported. HTTPS only provides protection for eavesdropping and man-in-the-middle attacks. When the information reaches the server or computer it is directed to, the information is then only as secure as that particular server or computer. If the implementation by the web browser, server software, and cryptographic algorithms is not correct, it is then possible for the information to be siphoned.

Most casual users of the Internet understand that HTTPS at the beginning of any URL in the address bar means that the connection is secure. This is a practical way for people who are unfamiliar with the dangers of hackers and other problems to be aware that they are using a secure messaging system. It is also frequently recommended, even on web pages, that people who do not see HTTPS at the beginning of the URL in the address bar should not enter any sensitive information, not only to protect the visitor to the website, but to protect the website’s reputation as well.

(ii) Briefly discuss the operation of Packet-Switched Network in your own word. Your discussion must contain AT LEAST 100 words. Please attach with the Packet-Switched Network diagram.

Packet-switched describes the type of network in which relatively small units of data called packets are routed through a network based on the destination address contained within each packet. Breaking communication down into packets allows the same data path to be shared among many users in the network. This type of communication between sender and receiver is known as connection less (rather than dedicated). Most traffic over the Internet uses packet switching and the Internet is basically aconnection less network.

Contrasted with packet-switched is circuit-switched, a type of network such as the regular voice telephone network in which the communication circuit (path) for the call is set up and dedicated to the participants in that call. For the duration of the connection, all resources on that circuit are unavailable for other users. Voice calls using the Internet's packet-switched system are possible. Each end of the conversation is broken down into packets that are reassembled at the other end.

Another type of digital network that uses packet-switching is the X.25 network, a widely-installed commercial wide area network protocol. Internet protocol packets can be carried on an X.25 network. The X.25 network can also support a virtual circuit in which a logical connection is established for two parties on a dedicated basis for some duration. A permanent virtual circuit (PVC) reserves the path on an ongoing basis and is an alternative for corporations to a system of leased lines. A permanent virtual circuit is a dedicated logical connection but the actual physical resources can be shared among multiple logical connections or users.

Packet-Switched Network diagram

(iii) Discuss the differences of cellular transmission General packet radio service (GPRS) and 4G in your own word. Provide with ONE (1) limitation of GPRS.

GPRS stands for General Packet Radio Service and it is the slowest one, it is a data connection standard available in GSM networks - the second generation cellular networks (2G). GSM traditionally work on 900, 1800 and 1900 MHz and they were initially designed for circuit-switched voice service. Channels are spaced 200 kHz, usually several of them per base station, each channel having 8 time-slots. A single voice connection would occupy one time slot, so this is a combination of FDD and TDD - Frequency Division Duplex and Time Division Duplex. Later came HSCSD (circuit switched data) which worked in a similar manner to a dial-in modem connection, but it was GPRS that made the wireless cellular data revolution - in GPRS data is sent in packets, just like on computer networks (as opposed to circuit-switching). This of course required a major redesign of the operator's core network, adding packet-switching nodes to support IP packet data, hence a GSM network with GPRS is sometimes called 2.5G. Expect speeds of several tens of kbps.

`Limitation of GPRS: Speeds Much Lower in Reality

Achieving the theoretical maximum GPRS data transmission speed of 172.2 kbps would require a single user taking over all eight timeslots without any error protection. Clearly, it is unlikely that a network operator will allow all timeslots to be used by a single GPRS user. Additionally, the initial GPRS terminals are expected be severely limited - supporting only one, two or three timeslots. The bandwidth available to a GPRS user will therefore be severely limited. As such, the theoretical maximum GPRS speeds should be checked against the reality of constraints in the networks and terminals. The reality is that mobile networks are always likely to have lower data transmission speeds than fixed networks.

RESULT: Relatively high mobile data speeds may not be available to individual mobile users until Enhanced Data rates for GSM Evolution (EDGE) or Universal Mobile Telephone System (UMTS) are introduced.

4G - 4th generation network called LTE (Long Term Evolution), works in a very different manner than 2nd and 3rd generations. Shared access is done by OFDMA - the available channel is divided into sub channels (also called sub carriers) and each of them is treated separately; groups of those sub carriers are assigned to different mobile phones. Also LTE is designed as a data-only network so all of the traffic is IP-based and there are no more circuit-switched connections. In fact unless the operator has VoLTE service (Voice over LTE), your 4G connection will only handle sending data, and to make/receive a voice call your phone will have to fall back to a 2G or 3G network. Of course the data speeds will be quite higher, you can expect tens of Mbps.

(iv)Attach a video clip discussing about the history of Internet at the end of the post