Download Document

The Internet Book
Chapter 15
Communication Protocol
• A common language
computers use to
exchange messages.
–Specifying exact format
and meaning of each
message
–Sending and receiving
3
Basic Functionality: Internet
Protocol (IP)
• IP defines computer
communication details.
–Specifying how packets are formed
–Specifying how routers forward each
packet
• Computers connecting to the
Internet must follow the IP rules.
4
IP Software On Every Machine
• Computer hardware does not
understand IP.
–Connecting a computer to the
Internet does not mean it can use
the Internet
• Computers need IP software
before using the Internet.
5
Internet Packets Are Called
Datagrams
• IP Datagrams are
packets that follow the
IP specifications.
– Traveling across the
Internet independent of
sender
6
The Illusion Of A Giant
Network
• Any computer can send IP
datagrams to any other computer
providing they have IP software
installed.
• The Internet operates like a virtual
network.
7
Figure 15.1
Figure 15.1 The view of the Internet that IP software provides. Users and application
programs treat the Internet like a single large network that allow arbitrary numbers of
computers to communicate.
The Reality Of Internal
Structure
• The Internet contains a complex
physical structure users never
see
–Interconnecting networks with
routers
9
Figure 15.2 A small example of the physical structure that remains hidden inside the Internet. Each computer
attaches to a single network; routers interconnect the networks.
Figure 15.2
Datagrams Travel In Packets
• IP datagram defines a standard for
all Internet packets. Routers:
–Encloses the data before sending
out the packet
11
Every Computer Is Assigned A
Unique Address
• Each computer attached to the
Internet must be assigned a
unique address.
12
Internet Addresses
• The unique number assigned to
a computer is its Internet (IP)
address.
• Each computer (including
routers) need to have an IP
address.
13
An Odd IP Address Syntax
• Computer stores IP address in
four binary units called bytes.
14
IP Addresses Are Not Random
• IP addresses are not random.
• Computers on the same
network have the same prefix.
15
A Trip Through The Internet
• A router must choose between
two paths that both lead to the
destination.
–Choosing the shortest path
16
Figure 15.3
Figure 15.3 An example of internet with six networks and three computers attached.
Conclusion
• Why is it important to have the
Internet protocol scheme?
18
Glossary
• Protocol
•
•
– The rules two or more computers must
follow to exchange messages
Internet Protocol
– (IP) Specification for the format of
packets computers use when
communicating across the Internet
IP Datagram
– A packet of data sent across the Internet
20
Glossary
• Virtual Network
•
– Appearance of a single, seamless
network system
Internet Address
– (IP Address) An unique number
assigned to a computer attached to
the Internet
21