Network Theory OSI and TCP/IP Models

uptightexampleNetworking and Communications

Oct 24, 2013 (3 years and 8 months ago)

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Network Theory


OSI and
TCP/IP Models

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Internetworking:

An Overview

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What is Networking?


Networking

-

the interconnection of
workstations, peripherals, terminals
and other devices*




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Yesterday’s Networks


The advent of the desktop PC brought
with it small, closed networks in the
mid
-
1980s.

An old
-
school LAN (local
-
area network)

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Today’s Computer Networks


Today, networks are everywhere:


School, work, home


Coffee shops, airports, state parks


Emerging technologies such as
EV
-
DO

and
WiMAX

promise
metro
-
wide networks in the air.

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What happened?


Over the past 20 years, computer
networks have evolved:




Small, proprietary, closed systems

One huge, global, collection of
networks (an
internetwork
)

The Internet

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What happened?


Vendors realized that standardizing
their products would help them make
money.


Various groups got together and
proposed networking standards.


The Internet (b.1969) offered an
attractive
de facto

set of standards.

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Network Protocols and
Standardization

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Network Protocols


Early networks:


proprietary technologies


single vendor only


Today:


Standards
-
based technologies


Macs, PCs, cell phones, watches, toasters, and
earrings can all share data as long as they all
speak to each other according to the same set of
rules, or
protocol
.


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Network Protocols


Protocol

-

a set of rules, or an agreement,
that determines the format and
transmission of data.


SNA

(Systems Network Architecture) = IBM

IPX

(Internet Packet eXchange) = Novell

IP

(Internet Protocol) = US Department of Defense

XNS

(Xerox Network System) = Xerox

NetBEUI

(NetBIOS Extended User Interface) = IBM

AppleTalk

= Apple

DECnet

= Digital Equipment Corporation

VINES

= Banyan

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TCP/IP: Internet Protocol


One protocol has become the
de facto

standard for
all computer networks.


IP v4 = The Internet Protocol (version 4)


All hosts on the Internet use the IP protocol


The Internet actually uses a family, or
suite
, of
protocols called
TCP/IP

which includes:


TCP, or Transmission Control Protocol:
(adds reliability
and sequencing to Internet conversations)


HTTP:

(web stuff)



FTP:

(file transfer)


DNS:

(naming system that brought us .com and www)


SMTP:

(mail, SPAM, and other delights of the Info Age)

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TCP/IP: Internet Protocol

All of these devices use the TCP/IP protocol “stack” to communicate.
In this case, they are using HTTP to browse the web.

All of these
devices need
an IP Address
to be on the
Internet
.

TCP/IP’s
developers
never envisioned
that this protocol
could support a
global network of
entertainment
and commerce.

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Reality Check


In the mid
-
1980s, Cisco (like all other
vendors) focused on “multi
-
protocol”
platforms.


Because TCP/IP has emerged as the
dominant protocol, our focus is entirely
on
IP networks
.


So, this is an Introduction to Cisco IP
Network Devices

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Types of Networks

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LANs


Local
-
Area Networks (LANs) emerged
in the mid 1980s


LANs


connects workstations, peripherals, and
other devices in a single building


LANs made it possible to efficiently share
such things as files and printers


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Early LANs Isolated

Seattle

San Francisco

New York

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Wide Area Networks (WANs)

Seattle

San Francisco

New York

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LAN, CAN, MAN, and WAN


LAN

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limited geographic area


office, home, small building (enterprise)


CAN

-

Campus
-
Area Network


University, Company Tech Center (enterprise)


MAN

-

Metropolitan
-
Area Network


citywide network, (typically involves a service provider)


WAN

-

large geographic area


city
-
to
-
city, worldwide, Internet (typical involves a service
provider)


PAN



personal area network


Cell phone, watch, PDA, bluetooth stuff (you!)



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LAN vs WAN


Early LANs and WANs typically used very different:


Protocols


Devices


Signaling


Media (physical connections, wire, RF)

Typical Early LANs

Typical Early WANs

High bandwidth

Low bandwidth

Cheap

Costly

Intermittent, on
-
demand connectivity

Always “on”

Small geographical area

Large geographical area

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Early LAN vs WAN


Different network types, different devices:

Hub, Repeater

Bridge

LAN Switch

Router

Modem, CSU/DSU

Switch

Access Server

Router

Common LAN Devices

Common WAN Devices

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Early LAN vs WAN


Emerging technologies and dominance of TCP/IP
spurred widespread adoption of new device types:

Switch

Multilayer Switch

Firewall

Router

Today’s LAN Devices

DSLAM

Optical Transport

Router

Today’s WAN Devices

VPN Gateway

IP Telephony (LAN/WAN)

IP Phone

IP PBX

Wireless (LAN/WAN)

Bridge

Access Point

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Today’s LAN/WAN


Several factors have blurred the
distinctions between WANs and LANs
and the devices that operate in each.


However, for the purposes of our
discussions, we will talk about devices
as either “LAN” or “WAN”

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The OSI Reference Model

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Enter ISO


ISO



International Organization for
Standardization (Geneva)


Voluntary, non
-
treaty organization charted by the UN


From the earliest days of networking, it
was clear to ISO that standards were
needed.


Standardization aids: development,
interoperability, education…

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ISO’s OSI Model


ISO looked at existing network
protocols (TCP/IP, XNS, SNA) and
came up with OSI RM.


OSI RM

-

Open Systems
Interconnection Reference Model

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OSI Reference Model

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7
-

Application Layer


Network processes to
applications


Provides network services
to user applications

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6


Presentation Layer


Data Representation


Code Formatting


Negotiation of data
transfer


Ensures information sent
by the application can be
transmitted on the network


Data encryption

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5


Session Layer


Interhost communication


Establishes, maintains,
and manages sessions
between applications

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4


Transport Layer


End
-
to
-
end connections


Segmentation


Reassembly into data
stream


Offers potential of reliable
transport

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3


Network Layer


Addresses and best path


Logical addressing is used
at this layer


IP, AppleTalk, IPX, etc.


Routers reside at this layer


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2
-

Data
-
Link Layer


Access to media


Physical transmission
across the medium


Error notification, network
topology and flow control


Uses MAC (physical)
addresses


Switches and bridges
reside at this layer

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1


Physical Layer


Binary Transmission


Provides the electrical,
mechanical, procedural
and functional means for
activating and maintaining
the physical link between
systems.


The media resides at this
layer

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Data Encapsulation Example

End
System

Intermediate
Systems

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Data Encapsulation

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TCP/IP vs OSI Model

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Cisco Networking

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Brief(est) History of LANs

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Early LANs


In the 1980s, several LAN technologies
competed to offer Layer 1/Layer 2 services:


Token Ring (IBM)


Ethernet (Xerox, et al)


ARCnet (Datapoint)


Later on:


FDDI, Fiber Distributed Data Interface


ATM, Asynchronous Transfer Mode

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The IEEE Working Groups

802.1

802.2

802.3

802.4

802.5

802.6

802.7

802.8

802.11

Networking Overview and Architecture

Logical Link Control

Ethernet

Token Bus

Token Ring

MANs

Broadband

Fiber Optic

Wireless Ethernet

...and more!

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Today


Ethernet is the
de facto

standard.


It has crushed its competitors in the
LAN space, and has been adopted for
Wireless networks and Metro WANs.

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Ethernet and TCP/IP


Ethernet and TCP/IP are the most pervasive
protocols

Data Link Layer

Physical Layer

Network Layer

Session Layer

Transport Layer

Presentation Layer

Application Layer

TCP/IP

Ethernet

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Device Functions at Layers