UNIT 5 MANAGING COMPUTER NETWORKS LEVEL 3 NETWORK PROTOCOLS

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1 UNIT 5 MANAGING COMPUTER NETWORKS LEVEL 3 NETWORK PROTOCOLS

2 NETWORK PROTOCOLS A network manager needs to be aware of a number of different protocols, especially those that exist in the Application Layer of the 7-layer ISO OSI model. These protocols can be implemented on many different types and sizes of computer platforms (e.g. Apple Mac, PC running Microsoft Windows, PC running Linux, Nintendo Wii, Sony PSP etc.). Each protocol uses a specific network port (or ports) and these must be left open in any software or hardware firewall in order for the protocol to work properly.

3 NETWORK PROTOCOLS Network protocols are formal standards and policies comprised of rules, procedures and formats that define communication between two or more devices over a network. Network protocols govern the end-to-end processes of timely, secure and managed data or network communication.

4 TASK: DESCRIBE THE MAIN FUNCTION OF THESE PROTOCOLS: Protocol Research, give the full name, OSI layer and a brief description. SNMP ICMP FTP TFTP HTTP NTP

5 HTTP HTTP functions as a request response protocol in the client server computing model. A web browser, for example, may be the client and an application running on a computer hosting a website may be the server. The client submits an HTTP request message to the server. The server, which provides resources such as HTML files and other content, or performs other functions on behalf of the client, returns a response message to the client. The response contains completion status information about the request and may also contain requested content in its message body. HTTP has many different status codes; code 200 is used to indicate that the request was fulfilled. 109 is the size of the object sent back to the browser client; Test.html is actually 109 bytes in size.

6 HTTP HTTP is designed to permit intermediate network elements to improve or enable communications between clients and servers. High-traffic websites often benefit from web cache servers that deliver content on behalf of upstream servers to improve response time. Web browsers cache previously accessed web resources and reuse them when possible to reduce network traffic. HTTP proxy servers at private network boundaries can facilitate communication for clients without a globally routable address, by relaying messages with external servers. HTTP is an application layer protocol designed within the framework of the Internet protocol suite. Its definition presumes an underlying and reliable transport layer protocol and Transmission Control Protocol (TCP) is commonly used. However HTTP can be adapted to use unreliable protocols such as the User Datagram Protocol (UDP), for example in HTTPU and Simple Service Discovery Protocol (SSDP).

7 FTP The File Transfer Protocol (FTP) is a standard network protocol used for the transfer of computer files from a server to a client using the Client server model on a computer network. FTP is built on a client-server model architecture and uses separate control and data connections between the client and the server. FTP users may authenticate themselves with a clear-text sign-in protocol, normally in the form of a username and password, but can connect anonymously if the server is configured to allow it. For secure transmission that protects the username and password, and encrypts the content, FTP is often secured with SSL/TLS (FTPS). It is not uncommon for a network manager to enforce a strict communications policy that prevents the use of FTP clients to download files from remote servers. This is often done to reduce the likelihood of illegal downloads, virus infection or the knowing installation of prohibited software on workstations. Such measures could be performed by simply blocking those network ports most commonly associated with the protocol (i.e. ports 20 and 21) on the network s primary firewall.

8 TFTP Trivial File Transfer Protocol (TFTP) is a simple lockstep File Transfer Protocol which allows a client to get a file from or put a file onto a remote host. One of its primary uses is in the early stages of nodes booting from a local area network. TFTP has been used for this application because it is very simple to implement. As with FTP, Microsoft Windows has native command-line interface (CLI) client support for TFTP but does not include a TFTP server (unlike UNIX and many Linux distributions).

9 Network Protocols Network protocols are layered such that each one relies on the protocols that underlie it Sometimes referred to as a protocol stack

10 KNOWLEDGE CHECK A For synchronising time on network clients 1 SNMP B For uploading and downloading files from network devices 2 NTP C For performing file transfers 3 TFTP D For returning diagnostic information on network data transfers, especially pinging 4 FTP E For performing network management and monitoring 5 ICMP

11 CONCLUSION Discussed types of Network protocols. Discussed the functions of network protocols. Considered the purpose of network protocols.