Transcript ONE Spring Hands-On Institute

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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
TCP/IP’s
developers
never envisioned
that this protocol
could support a
global network of
entertainment
and commerce.
All of these
devices need
an IP Address
to be on the
Internet.
All of these devices use the TCP/IP protocol “stack” to communicate.
In this case, they are using HTTP to browse the web.
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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
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Seattle
New York
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San Francisco
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Wide Area Networks (WANs)
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Seattle
New York
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San Francisco
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LAN, CAN, MAN, and WAN
• LAN - 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:
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Protocols
Devices
Signaling
Media (physical connections, wire, RF)
Typical Early LANs
Typical Early WANs
Always “on”
Intermittent, on-demand connectivity
High bandwidth
Low bandwidth
Cheap
Costly
Small geographical area
Large geographical area
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Early LAN vs WAN
• Different network types, different devices:
Common LAN Devices
Common WAN Devices
Hub, Repeater
Modem, CSU/DSU
Bridge
Switch
LAN Switch
Access Server
Router
Router
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Early LAN vs WAN
• Emerging technologies and dominance of TCP/IP
spurred widespread adoption of new device types:
Today’s LAN Devices
Switch
Today’s WAN Devices
Wireless (LAN/WAN)
Bridge Access Point
Multilayer Switch
VPN Gateway
DSLAM
IP Telephony (LAN/WAN)
Optical Transport
Firewall
Router
IP Phone
IP PBX
Router
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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 Networking Overview and Architecture
802.2 Logical Link Control
802.3 Ethernet
802.4 Token Bus
802.5 Token Ring
802.6 MANs
802.7 Broadband
802.8 Fiber Optic
802.11 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
Application Layer
Presentation Layer
Session Layer
TCP/IP
Transport Layer
Network Layer
Data Link Layer
Physical Layer
Ethernet
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Device Functions at Layers
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