notes -

screechingagendaΔίκτυα και Επικοινωνίες

26 Οκτ 2013 (πριν από 4 χρόνια και 6 μήνες)

115 εμφανίσεις

Internet Architecture


IP address
/internet address

Internet Protocol address

IP address

is assigned to
each device like a computer or a printer

on a network has a unique identifier. Just as you would
address a letter to send in the mail, computers use the
unique identifier to send data to specific computers on
a network. Most networks today, including all
computers on the
, use the TCP/IP protocol to
communicate on
network. In the TCP/IP protocol, the
unique identifier for a computer is called its IP address.

How does your computer get i
ts IP address?

An IP address can be either dynamic or static. A static address is one that you configure yourself by
editing your computer's network settings. This type of address is rare, and it can create network
issues if you use it without a good unde
rstanding of TCP/IP. Dynamic addresses are the most
common. They're assigned by the Dynamic Host Configuration Protocol (DHCP), a service running on
the network. DHCP typically runs on network hardware such as

or dedicated DHCP servers.

An IP address is broken down into two parts




This number identifies the network on which the
hosts resides

These numbers identifies the host itself.


Hypertext Transfer
Protocol, HTTP is a set of standards
that allow users of the World Wide Web to exchange
information found on web pages. When wanting to
access any web page enter http:// in front of the web
address, which tells the browser to communicate over
. For exa
mple, the full URL
.com. Today's modern browsers
no longer require HTTP in front of the URL since it is the
default method of communication. However, it is still used in browsers because of the need to
access other protocols such a
s FTP through the browser. Below are a few of the major facts on HTTP.

Internet Architecture



HTTPS stands for Hypertext Transfer Protocol Secure and is a
combination of Hypertext Transfer Protocol (HTTP) and SSL/TLS
protocol. HTTPS provides encrypted communication
and secure
identification of a network web server. The main idea of HTTPS is
to encrypt your data and establish a secure channel over a non
secure network to ensure data being transferred is protected
from eavesdroppers and hackers who want to intercept an
access your data.

How Do You Know If Your Connection Is Secure?

Before keying in any personal /financial information on any website, make sure that the URL starts
with “HTTPS” and that there is a padlock sign on the navigation bar or footer of your bro
wser as
shown on the below images:

What Are The Benefits Of HTTPS?

HTTPS provides a higher level of security because data sent and received over this
protocol are encrypted.

Data encrypted with HTTPS cannot be decrypted by a third party who may want to
the information.

HTTPS connections are more secure for online payment transactions compared to HTTP


SMTP stands for Simple Mail Transfer
Protocol. It's a set of communication
guidelines that allow software to transmit
email over

the Internet. Most email software
is designed to use SMTP for communication
purposes when sending email, and It only
works for outgoing messages. When people
set up their email programs, they will typically
have to give the address of their Internet
ce provider's SMTP server for outgoing mail. There are two other protocols


that are used for retrieving and storing email.

SMTP provides a set of codes that simplify the communication of email messages between servers.
It's a kind of shor
thand that allows a server to break up different parts of a message into categories

Internet Architecture


the other server can understand. Any email message has a sender, a recipient

or sometimes
multiple recipients

a message body, and usually a title heading. From the pers
pective of users,
when they write an email message, they see the slick interface of their email software, but once that
message goes out on the Internet, everything is turned into strings of text. This text is separated by
code words or numbers that identi
fy the purpose of each section. SMTP provides those codes, and
email server software is designed to understand what they mean.

TTL (time to live)

The time
live (TTL) is the number of


is permitted to travel before being
discarded by a router.

TTL is used when a "ping," or a request for a
response, is sent to another computer, such as a
server. The TTL represents the number of hops,
or servers in different locations, the request can
travel to before returning a failed attempt

A packet is the fundamental unit of information
transport in all modern computer
, and
ingly in other communications networks as well. A router is a network layer electronic device
and/or software that connects at least two networks, such as two

(local area networks) or

(wide area networks), and forwards packets between them. A hop is the trip that a packet
takes from one router to another as it traverses a network on the way to its destination.

Check Sum

This is storedin

the packets header if the 2 che
ck sum are identical is invalid.
A checksum is a count
of the number of bits in a transmission unit that is included with the unit so that the receiver can
check to see whether the same number of bits arrived. If the counts
match, it's assumed that the
complete transmission was received. Both


communication layers provide a checksum
ount and verification as one of their services