Network address translation (NAT).
There are two types of NAT,
one-to-one NAT and one-to-many NAT.
One-to-one NAT is known as basic NAT.
And it enables interconnection of two
incompatibly addressed assigned IP networks.
For example, if there's an address structure within
a company that is used in an address structure outside, well,
typically, the address structure outside may
have a problem when connecting to address,
an IP address, within the company network.
And therefore, this is when basic NAT,
one-to-one NAT, can be very effective.
One-too-many NAT is also known as IP masquerading.
An address space that includes many private IP addresses
can be hidden under a single public IP address that is used externally.
For example, these private IP addresses may be using
one representative IP address when they connect to the Internet.
Some of the advantages of one-too-many NAT include,
it provides enhanced security,
and also it was made such that we could save
public IPv4 addresses which we are running out very quickly.
RPC which is Remote Procedure Call.
In RPC, this is a program that enables
a function/procedure to be executed on a remote computer.
It enables easy programming as if the function is
to run on a local computer that is currently being used.
Recovery procedures from unpredictable network problems are needed.
RPC request and response procedures include,
a client initiates RPC by sending a request message with a set of
parameters to a remote server and the server
replies with a response to the client.
FTP, file transfer protocol.
FTP is used to transfer files from a server to a client computer.
It is used over TCP/IP based upon the internet standard RFC 959.
FTP sign-in protocol commonly requires a username and a password.
An FTP with TLS (Transport Layer Security) protection,
which we call FTPS, is commonly used.
FTP must include active mode and passive mode.
In FTP active mode,
a client sends a FTP command port M to the server to inform which port to use.
Server sends data from its FTP server data port to the client's port.
FTP passive mode is used when the client is behind
a firewall and cannot accept incoming TCP connections from the server.
The client uses the control connection to send a passive command to the server.
The server sends its IP address and server port number.
The client opens data connection to the server IP address and port number.
FTP active and passive modes were updated to support
IPv6 and enhanced passive mode in our RFC 2428.
FTP data transfer modes include stream mode,
block mode, and compressed mode.
Stream mode is, TCP used to send data in
a continuous stream and FTP does minimum processing.
In block mode, FTP divides data into blocks and uses TCP to transfer.
In compressed mode, data compression,
for example, run-length encoding is applied.
Enhanced data transfer techniques exist.
Email.
Now we are going to compare POP3 and IMAP.
They are both email retrieval applications that use TCP and IP.
POP3 stands for Post Office Protocol version 3.
IMAP stands for Internet Message Access Protocol version 4.
Encryption through TLS and STARTTLS or SSL can be used.
POP3 has a very simple operation.
It moves emails from the server onto your device.
POP3 can be set to leave emails on the server after being retrieved.
In IMAP, IMAP enables complete management of
a user mailbox on the server from multiple e-mail devices such as your PC,
your smartphone, and your notebook computer,
your laptop computer, and other devices.
IMAP is more popular due to multiple device support.
IMAP uses more complex queries because it needs to support multiple devices.
It leaves emails on the server after retrieval
and it's left there until the email is deleted by the user.
SMTP stands for Simple Mail Transfer Protocol.
It is an Internet e-mail protocol.
It is text-based and it uses TCP/IP.
It is commonly used to send and receive emails between servers.
These are the references that I use and I recommend them to you. Thank you.