Internetworking: Concepts, Architecture, and Protocols - Chaminade ...

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24 Οκτ 2013 (πριν από 3 χρόνια και 11 μήνες)

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1

Internetworking

Prof. Martins

Department of Computer Science and
Computer Information Systems

2

Goals


In this chapter you will learn about
internetworking:


The motivation


The hardware


The architecture



3

The Motivation for
Internetworking


Each network technology is designed to
fit a specific set of constraints


LAN technologies provide high speed
communications across short distances


WAN technologies are designed to provide
communications across large areas


No single networking technology is best
for all needs

4

The Concept of Universal
Service


A communication system that supplies
universal service allows arbitrary pairs
of computers to communicate.
Universal service is desirable because it
increases individual productivity.

5

A Universal Service in A
Heterogeneous World


Although universal service is highly
desirable, incompatibilities among
network hardware and physical
addressing prevent an organization
from building a bridged network that
includes arbitrary technologies.

6

Internetworking


Despite incompatibilities among
network technologies, researchers have
devised a scheme that provides
universal service among heterogeneous
networks, called
Internetworking.


7

Physical Network Connection
with Routers


The basic hardware component used to
connect heterogeneous networks is a
router.


Routers resemble bridges (physically)


Each router is a special
-
purpose hardware
system dedicated to the task of
interconnecting networks.


The network treats the connection to a router
the same as a connection to any computer.

8

Physical Network Connection
with Routers

Fig. 17.1


Two physical networks connected by a router, which
has a separate interface for each network connection. Computers
can attach to each network.

9

Internet Architecture

Fig. 17.2


An Internet formed by using three routers to interconnect
four physical networks. Each network can be a LAN or a WAN

10

Achieving Universal Service


The goal of internetworking is “
universal
service across heterogeneous networks



Routers must agree to forward information
from a source on one network to a specified
destination or another.


This task is complex because frame formats
and addressing schemes used by the
underlying networks can differ.


11

Achieving Universal Service


Protocol software is needed on
computers and routers to make
universal service possible.


Internet protocols overcome
differences
in frame formats and physical address

to make communication possible among
networks that use different
technologies.

12

A Virtual Network


Internet software provides the appearance
of a single,
seamless communication system


The system offers
universal service
: each
computer is assigned an address, and any
computer can send a packet to any other
computer.


Internet protocol
hides the details

of physical
network connections, physical addresses, and
routing information.

13

A Virtual Network


An internet is a
virtual network

system:
the communication system is an
abstraction.


Although a combination of hardware
and software provides the
illusion of a
uniform network system,

no such
system exists.

14

A Virtual Network

Fig. 17.3


The Internet concept:

(a) The illusion of a single network
that TCP/IP software provides to
users and applications, and

(b) the underlying physical structure
in which a computer attaches to one
physical network, and routers
interconnect the networks.

15

Protocols For Internetworking


One suite stands out as the most
widely used for internetworking: The
TCP/IP


TCP/IP
was the first set of protocols
developed for use in an internet.


TCP/IP origins: ARPA, 1970s


NSF and others: mid
-
1980s

16

Layering and TCP/IP Protocols

Figure 17.4 The five layers of the TCP/IP reference model

17

Layering and TCP/IP Protocols


Layer 1



Physical
:

corresponds to basic
network hardware just as Layer 1 in the
ISO 7
-
layer reference model


Layer 2
-

Network Interface:
protocols
specify how to organize data into
frames and how a computer transmit
frames over a network. Similar to layer
2 protocols in the ISO reference model.

18

Layering and TCP/IP Protocols


Layer 3
-

Internet:
Specify the
format of
packets

sent across an internet as well
as the
mechanisms

used to forwards
packets from a computer through one
or more routers to a final destination.

19

Layering and TCP/IP Protocols


Layer 4
-

Transport:
Specify how to
ensure reliable transfer (like layer 4 in
the ISO model)


Layer 5
-

Application:
corresponds to
layers 6 and 7 in the ISO model. Each
layer 5 protocol specifies how one
application uses an internet.


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To summarize:


TCP/IP protocols are organized into five
conceptual layers. Although some
layers of the TCP/IP reference model
correspond to layers of the ISO
reference model,
the ISO layering
scheme does not have a layer that
corresponds to TCP/IP’s Internet Layer
.

21

Host Computers, Routers and
Protocol Layers


TCP/IP defines the term
host computer

to
refer to any computer system that connects
to an internet and runs applications


A host can be as small as a personal
computer or as large as a mainframe.


TCP/IP protocols make it possible for any pair
of hosts to communicate, despite hardware
differences.

22

Host Computers, Routers and
Protocol Layers


Both hosts and routers need TCP/IP
protocol software.


A router does not need Layer 5
protocols for applications

(such as FTP,
since routers do not run such
applications)


23

Summary


Physically, an internet is a collection of
networks interconnected by devices
called routers


Conventional computers that connect to
an internet are called hosts


Logically, an internet appears to be a
single, seamless communication system

24

Summary


The illusion of a single communication
system is provided by internet protocol
software.


The most important protocols
developed for internetworking are
known as the TCP/IP Internet Protocols.


TCP/IP protocol software works well
and handles large internets.

25

Summary


In addition to being used on many
private internets, TCP/IP is used on the
global Internet that reaches over 82
million computers in 210 countries.