Computer Networks

It collects and exchanges network management information between a network management console and network devices.

It provides a one to one or one to many, connectionless and unreliable communication service.

It is a protocol that routers use to exchange routing information on an IP network.

It establishes connections, sequences and acknowledges packet sent and recovers packets lost during transmission.

This services can be thought of as different layers that use lower-level services to provide services to higher-level services.

DNS primarily uses User Datagram Protocol (UDP) on port number 53 to serve requests.

These are used for low speed data communications between PCs and very small computers.

Time to live (TTL) or hop limit is a mechanism that limits the lifespan or lifetime of data in a computer or network. TTL may be implemented as a counter or timestamp attached to or embedded in the data. Once the prescribed event count or timespan has elapsed, data is discarded.

In Optimal Page Replacement Policy, when a page needs to be swapped in, the operating system swaps out the page whose next use will occur farthest in the future.

Internet Control Message Protocol (ICMP) is used to test the internet. ICMP messages are typically used for diagnostic or control purposes or generated in response to errors in IP operations.

Simple Network Management protocol is a framework used for managing devices on internet using the TCP/IP protocol suit.Its a application level protocol and provides set of fundamental operations for  monitoring and maintaining on internet.It uses the concept of agent and manager.A manager is a host, that controls and monitors a set of agents therfore it is correct.

NFS stands for Network File System. It allows a system to share directories and files with others over a network. By using NFS, users and programs can access files on remote systems almost as if they were local files.

It is the shortest frame which consists of flag, address, control, FCS and it carries commands and responses.

 FTP, SFTP and TFTP are used for transferring files from one system to another through internet and web server. FTP  is a standard network protocol used to copy a file from one host to another over a TCP -based network, such as the Internet. The SSH File Transfer Protocol is not related to FTP except that it also transfers files and has a similar command set for users. A similar protocol TFTP (Trivial File Transfer Protocol) provides connectionless file transfer over UDP.This is only suitable for very small files; for example, uploading configuration files to routers. 

X.25 is a subset of HDLC protocol. It enables to form a logical link connection, besides all the other characterstics of HDLC.