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  • Routers can also be used to interconnect different types of network such as Token Ring and Ethernet networks. In such case Router changes the packetís size and format to fit the type of destination network on which the packets is being sent. Routed Protocol is that LAN protocol that can be transmitted to other network by way of Router. For e.g. IP, AppleTalk, DECnet and SPX.

  • TCP / IP [DOD] Protocol Suite




FTP [File Transfer Protocol]


TFTP [Trivial File Transfer Protocol]


SMTP [Simple Mail Transfer Protocol]


TELNET [Terminal Emulation]


SNMP [Simple Network Management Protocol]


DHCP [Dynamic Host Configuration Protocol]


DNS [Domain Name Service]


HOST to Host

TCP [Transmission Control Protocol]


UDP [User Datagram Protocol]


IP Internet Protocol


ICMP Internet Control Message Protocol


ARP Address Resolution Protocol


RARP Reverse Address Resolution Protocol








  • It allows a user on remote client machine, called the Telnet Client, to access the resource of another machine (Telnet Server). On client it gives text mode type menus that give users the opportunity to choose option and access the applications on server. User begins a Telnet session by running Windows :- Hyper Terminal Option.



  • File Transfer Protocol helps to transfer files. FTP isnít just a protocol, itís also a program. Operating as a protocol, FTP is used by applications to Upload / Download files on Web or FTP Server. It allows to access directories and files, users are subjected to authenticate on server via login password.



  • Trivial File Transfer Protocol is the stripped down version of FTP. It is UDP based protocol that can transfer configuration files and Cisco IOS software images between systems.



  • Simple Mail Transfer Protocol uses a spooled or queued method of mail delivery. One a mail has been sent to destination from any pc, the mail is spooled to another PC usually SMTP server. The software at server keeps a vigil and regular check for mail from all connected SMTP client computers. All the mails are stored and delivered to respective destination from single SMTP server. SMTP is used to send mail while POP3 is used to receive mail.



  • Simple Network Management Protocol collects and manipulates valuable network information. It gathers data by polling the devices on the network from management station at fixed or random intervals, requiring them to disclose certain information. When all is well SNMP receives something called BASELINE. BASELINE is a report delimiting the operational traits of a healthy network. This protocol can also stand as a watchdog over the network. It quickly notify manager for any sudden turn of event. These network watchdogs are called Agents and when any abnormal activities are occurred, agent send alter called a trap to the management station. Most software house, corporate and IT firms keep vigil through SNMP.



  • Domain Name Service resolves hostnames to IP address. DNS was designed to make our lives easier. Think about this: if you need to remember the IP address of all the websites that you visit, it will be very difficult to remember the IP addresses of thousands of Web sites. DNS resolves the FQDN [Fully Qualified Domain name to IP Address and vice-versa. So when one type FQDN for e.g. in any web browser, DNS can locate IP address based on its FQDN name and you can communicate easily.



  • Dynamic Host Configuration Protocol assigns IP addresses to hosts. It allows easier administration and works well in small to large network environments. Most hardware can be used as a DHCP server, including Cisco Router. On DHCP server one specify SCOPE i.e. range of IP address to assign, Exclude. Depending upon scope host connected will get IP Address, Subnet mask etc. DHCP uses a four-step process to lease IP addressing information to DCHP clients. This process is referred to as DORA: Discovery, Offer, Request, and Acknowledgment.



  • Internet Protocol is essential for Internet layer. All other protocols found here merely exist to support it. We are aware that all interconnected network work only because networks have software and logical address called IP address. IP looks at each packetís address, then using a routing table it decides where a packets is to be sent next, choosing the best path. IP receives segments from Host-to-Host layer and fragments them into datagrams (Packets) if necessary. On receiving side IP then reassembles datagrams back into segments.



  • Internet Control Message Protocol works at the network layer and is used by IP for many different services. ICMP is a management protocol and messaging service provider for IP. It provides information to host about network problem. For e.g. if a router canít send an IP datagram (packets) any further, it uses ICMP to send a message back to the sender, advising it of the situation.



  • Address Resolution Protocol finds the hardware address of a host from a known IP address. When IP has a datagram to send, it must inform a Network Access Protocol, such as Ethernet or Token Ring, of the destinationís hardware address on local network. If IP doesnít find the destination hostís hardware address in ARP cache, it uses ARP to find destination IP address. ARP interrogates the local network by sending out a broadcast asking the computers with the specified IP address to reply with its hardware address.



  • Reverse Address Resolution Protocol When a computer happens to be a disk-less, it has no way of knowing and storing IP address. But it does know its MAC (Media Access Control) address. RARP send MAC address and request for IP address to RARP server, which in turns responds with IP address and resolve the MAC to IP identity. In short RARP resolves Ethernet MAC addresses to IP addresses.

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