You can think of a port as a phone extension, with the computer's IP address being like its phone number. You can call the number (IP address) to talk to the computer, then dial the extension (port) to talk to a specific application. An application needs to be listening on a port in order to communicate.
A protocol is just the language that the two applications on either end of a conversation agree to speak in. If your application is sending streams of bytes to my application, my application needs to know how to interpret those bytes.
Port numbers are use by TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) while Protocol numbers are reserved number used to identify protocols.
PC-------Network ---------web server
For example: PC contact to the web server’s port 80 to get the web page because HTTP uses well known port number of 80. PC also use a port number from the User port range as the source port (e.g. 1380). This port number is used by the web server to serve the webpage to PC i.e. web server send the page with source port of 80 and destination port of 1380.
In an IP header, the Protocol field identifies the service in the next higher level in the protocol stack to which data is passed.
[toc:faq]The ProblemOn traditional switches whenever we have a trunk
interface we use the VLAN tag to demultiplex the VLANs. The switch needs
to determine which MAC Address table to look in for a forwarding
decision. To do this we require the switch to do...
[toc:faq]Introduction:Netdr is a tool available on a RSP720, Sup720 or
Sup32 that allows one to capture packets on the RP or SP inband. The
netdr command can be used to capture both Tx and Rx packets in the
software switching path. This is not a substitut...
IntroductionOSPF, being a link-state protocol, allows for every router
in the network to know of every link and OSPF speaker in the entire
network. From this picture each router independently runs the Shortest
Path First (SPF) algorithm to determine the b...