Computer networks-4

In this video we are going to discuss
TCP/IP
High Level Protocols
MIME Types
Network Firewall
Network Addresses
Domain Name Server (DNS)

TCP/IP
TCP stands for Transmission Control Protocol
 TCP software breaks messages into packets, hands them off to the IP
software for delivery, and then orders and reassembles the packets at their
destination
IP stands for Internet Protocol
 IP software deals with the routing of packets through the maze of
interconnected networks to their final destination

TCP/IP (continue)
UDP stands for User Datagram Protocol
It is an alternative to TCP
The main difference is that TCP is highly reliable, at the cost of
decreased performance, while UDP is less reliable, but generally faster

High-Level Protocols
Other protocols build on the foundation established by the
TCP/IP protocol suite
Simple Mail Transfer Protocol (SMTP)
File Transfer Protocol (FTP)
Telnet
Hyper Text Transfer Protocol (http)

MIME Types
Related to the idea of network protocols and standardization
is the concept of a file’s MIME type
MIME stands for Multipurpose Internet Mail Extension
Based on a document’s MIME type, an application program can
decide how to deal with the data it is given

MIME Types
Figure : Some protocols and the ports they use

Firewalls
Firewall A machine and its software that serve as a special gateway to a
network, protecting it from inappropriate access
Filters the network traffic that comes in, checking the validity of the messages as much
as possible and perhaps denying some messages altogether
Enforces an organization’s access control policy

Firewalls
Figure : A firewall protecting a LAN

Network Addresses
Hostname A unique identification that specifies a particular computer on
the Internet
For example
matisse.csc.villanova.edu
condor.develocorp.com

Network Addresses
Network software translates a hostname into its
corresponding IP address
For example
205.39.145.18

Network Addresses
An IP address can be split into
network address, which specifies a specific network
host number, which specifies a particular machine in that network
Figure : An IP address is stored in four bytes

Domain Name System
A hostname consists of the computer name followed by the domain
name
csc.villanova.edu is the domain name
A domain name is separated into two or more sections that specify the
organization, and possibly a subset of an organization, of which the computer
is a part
Two organizations can have a computer named the same thing because the
domain name makes it clear which one is being referred to

Domain Name System
The very last section of the domain is called its top-level
domain (TLD) name
Figure : Top-level domains, including some relatively new ones

Domain Name System
Organizations based in countries other than US use a top-
level domain that corresponds to their two-letter country
codes
Figure : Some of the top-level domain names based on country codes

Domain Name System
The domain name system (DNS) is chiefly used to translate hostnames
into numeric IP addresses
DNS is an example of a distributed database
If that server can resolve the hostname, it does so
If not, that server asks another domain name server

Computer networks-4

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