Which of the following indicates to a packet where to go and how to communicate with the right service or protocol on the destination computer?

A.
Socket

B.
IP address

C.
Port

D.
Frame

Explanation:
A: UDP and TCP are transport protocols that applications use to get their data across a network. They both use ports to communicate with upper OSI layers and to keep track
of various conversations that take place simultaneously. The ports are also the mechanism used to identify how other computers access services. When a TCP or UDP message
is formed, a source and a destination port are contained within the header information along with the source and destination IP addresses. This makes up a socket, which is how
packets know where to goby the addressand how to communicate with the right service or protocol on the other computerby the port number. The IP address acts as the
doorway to a computer, and the port acts as the doorway to the actual protocol or service. To communicate properly, the packet needs to know these doors.
B is incorrect because an IP address does not tell a packet how to communicate with a service or protocol. The purpose of an IP address is host or network interface
identification and location addressing. Each node in a network has a unique IP address. This information, along with the source and destination ports, makes up a socket. The IP
address tells the packet where to go, and the port indicates how to communicate with the right service or protocol.
C is incorrect because the port only tells the packet how to communicate with the right service or protocol. It does not tell the packet where to go. The IP address provides this
information. A port is a communications endpoint used by IP protocols such as TCP and UDP. Ports are identified by a number. They are also associated with an IP address and
a protocol used for communication.
D is incorrect because frame is the term used to refer to a datagram after it is given a header and trailer at the data link layer. A message is formed and passed to the
application layer from a program and sent down through the protocol stack. Each protocol at each layer adds its own information (headers and trailers) to the message and
passes it down to the next level. As the message is passed down the stack, it goes through a sort of evolution, and each stage has a specific name that indicates what is taking
place. When an application formats data to be transmitted over the network, the data is called a message. The message is sent to the transport layer, where TCP does its magic
on the data. The bundle of data is now a segment. The segment is sent to the network layer. The network layer adds routing and addressing, and now the bundle is called a
datagram. The network layer passes off the datagram to the data link layer, which frames the datagram with a header and a trailer, and now it is called a frame.