© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-3
ObjectivesObjectives
On completion of this chapter, you will be able to perform the following tasks:• Describe how data traffic is exchanged
between source and destination devices
• Identify the roles and functions of a hub, switch, and router, and where they best fit in the network
• Select the appropriate Cisco equipment for a given set of network requirements
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-4
Defining Components of the Network
Defining Components of the Network
Main OfficeBranch Office
Home Office
Mobile Users
Internet
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-5
Floor 2
Floor 1
Server Farm
Defining the Components of a Network (cont.)
Defining the Components of a Network (cont.)
Branch Office
Telecommuter
ISDN
Remote Campus
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Network Structure Defined by Hierarchy
Network Structure Defined by Hierarchy
Distribution Layer
Core Layer
AccessLayer
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Access Layer CharacteristicsAccess Layer Characteristics
End station entry point to the network
Access Layer
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-8
Distribution Layer Characteristics
Distribution Layer Characteristics
• Access Layer Aggregation Point
• Routes traffic
• Broadcast/Multicast Domains
• Media Translation
• Security
• Possible point for remote access
Distribution Layer
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-9
Core Layer Characteristics Core Layer Characteristics
• Fast transport to enterprise services
• No packet manipulation
Core Layer
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OSI Model OverviewOSI Model Overview
Application (Upper) Layers
Session
Presentation
Application
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-11
OSI Model OverviewOSI Model Overview
Data Flow Layers
Transport Layer
Data Link
Network Layer
Physical
Application (Upper) Layers
Session
Presentation
Application
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Role of Application LayersRole of Application Layers
TelnetHTTP
User Interface
EXAMPLES
Application
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-13
TelnetHTTP
ASCIIEBCDICJPEG
User Interface
• How data is presented• Special processing such as encryption
EXAMPLES
Presentation
Application
Role of Application LayersRole of Application Layers
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-14
TelnetHTTP
ASCIIEBCDICJPEG
Keeping different applications’ data separate
User Interface
• How data is presented• Special processing such as encryption
Operating System/Application Access Scheduling
EXAMPLES
Session
Presentation
Application
Role of Application LayersRole of Application Layers
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-15
Keeping different applications’ data separate
User Interface
• How data is presented• Special processing such as encryption
TelnetHTTP
ASCIIEBCDICJPEG
Operating System/Application Access Scheduling
Transport Layer
Data Link
Network Layer
Physical
EXAMPLES
Session
Presentation
Application
Role of Application LayersRole of Application Layers
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-16
Role of Data Flow LayersRole of Data Flow Layers
EIA/TIA-232V.35
EXAMPLES
Physical • Move bits between devices• Specifies voltage, wire speed and
pin-out cables
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-17
802.3 / 802.2HDLC
EIA/TIA-232V.35
EXAMPLES
Role of Data Flow LayersRole of Data Flow Layers
Data Link
Physical
• Combines bits into bytes and bytes into frames
• Access to media using MAC address• Error detection not correction
• Move bits between devices• Specifies voltage, wire speed and
pin-out cables
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-18
802.3 / 802.2HDLC
EIA/TIA-232V.35
IPIPX
EXAMPLES
Role of Data Flow LayersRole of Data Flow Layers
Network
Data Link
Physical
• Combines bits into bytes and bytes into frames
• Access to media using MAC address• Error detection not correction
• Move bits between devices• Specifies voltage, wire speed and
pin-out cables
Provide logical addressing which routers use for path determination
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-19
TCPUDPSPX
802.3 / 802.2HDLC
EIA/TIA-232V.35
IPIPX
EXAMPLES
Role of Data Flow LayersRole of Data Flow Layers
Transport
Data Link
Physical
• Reliable or unreliable delivery• Error correction before retransmit
• Combines bits into bytes and bytes into frames
• Access to media using MAC address• Error detection not correction
• Move bits between devices• Specifies voltage, wire speed and
pin-out cables
Network Provide logical addressing which routers use for path determination
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-20
TCPUDPSPX
802.3 / 802.2HDLC
EIA/TIA-232V.35
IPIPX
Presentation
Application
SessionEXAMPLES
Role of Data Flow LayersRole of Data Flow Layers
• Reliable or unreliable delivery• Error correction before retransmit
• Combines bits into bytes and bytes into frames
• Access to media using MAC address• Error detection not correction
• Move bits between devices• Specifies voltage, wire speed and
pin-out cables
Transport
Data Link
Physical
Network Provide logical addressing which routers use for path determination
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-21
Encapsulating DataEncapsulating Data
Transport
Data Link
Physical
Network
Upper Layer Data
Upper Layer DataTCP Header
DataIP Header
DataLLC Header
0101110101001000010
DataMAC Header
Presentation
Application
Session
Segment
Packet
Bits
Frame
PDU
FCS
FCS
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-22
Upper Layer Data
De-encapsulating DataDe-encapsulating Data
LLC Hdr + IP + TCP + Upper Layer Data
MAC Header
IP + TCP + Upper Layer Data
LLC Header
TCP+ Upper Layer Data
IP Header
Upper Layer Data
TCP Header
0101110101001000010
Transport
Data Link
Physical
Network
Presentation
Application
Session
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-23
Application
Presentation
Session
Transport
Network
Data Link
Physical
OSI Model PDU Functional Responsibilities Examples
Written Exercise: OSI Model Written Exercise: OSI Model
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-24
Physical Layer FunctionsPhysical Layer Functions
Defines
• Media type
• Connector type
• Signaling type
Eth
ern
et
802.
3
V.3
5
Ph
ysic
al
EIA
/TIA
-232
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-25
Physical Layer: Ethernet/802.3Physical Layer: Ethernet/802.3
Hub
Hosts
Host
10Base2—Thick Ethernet10Base5—Thick Ethernet
10BaseT—Twisted Pair
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-26
Hubs Operate at Physical layerHubs Operate at Physical layer
A B C D
Physical
• All devices in the same collision domain
• All devices in the same broadcast domain
• Devices share the same bandwidth
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Hubs: One Collision DomainHubs: One Collision Domain
• More end stations means more collisions
• CSMA/CD is used
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-28
Data Link layer FunctionsData Link layer Functions
Defines• Physical source and
destination addresses
• Higher layer protocol (Service Access Point)associated with frame
• Network topology
• Frame sequencing
• Flow control
• Connection-oriented or connectionless
Dat
a L
ink
Ph
ysic
alEIA/TIA-232
v.35
Eth
ern
et
Fra
me
Rel
ay
HD
LC
802.2
802.3
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-29
DataSource add FCSLengthDest add
Variable266 4
0000.0C xx.xxxx
Vendor assigned
IEEE assigned
MAC Layer - 802.3
Data Link Layer Functions (cont.)Data Link Layer Functions (cont.)
Preamble
Ethernet II uses “Type” here and does not use 802.2.
MAC Address
8# Bytes
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-30
DataDest SAP
Source SAP
DataSource add FCSLengthDest add
Variable11
802.2 (SAP)
MAC Layer - 802.3
Data Link Layer Functions (cont.)Data Link Layer Functions (cont.)
Ctrl
1 or 2
3 2
Preamble
DataDest SAP
AASource SAP
AA
Variable11
802.2 (SNAP)
Ctrl
03
1 or 2
OR
OUI ID
Type
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-31
• Each segment has its own collision domain
• All segments are in the same broadcast domain
Data Link
Switches and Bridges Operate at Data Link Layer
Switches and Bridges Operate at Data Link Layer
OR1 2 3 1 24
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SwitchesSwitches
• Each segment has its own collision domain
• Broadcasts are forwarded to all segments
Memory
Switch
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Network Layer FunctionsNetwork Layer Functions
• Defines logical source and destination addresses associated with a specific protocol
• Defines paths through network
• Interconnects multiple data links
Net
wo
rk
IP, IPX
Dat
a L
ink
Ph
ysic
al
EIA/TIA-232v.35
Eth
ern
et
Fra
me
Rel
ay
HD
LC
802.2
802.3
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-34
DataSourceaddress
Destination address
IP
Network Layer Functions (cont.)Network Layer Functions (cont.)
Header
172.15.1.1
NodeNetwork
• Logical Address
Network Layer End Station Packet
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-35
Network Layer Functions (cont.)Network Layer Functions (cont.)
11111111 11111111 00000000 00000000
10101100 00010000 01111010 11001100
BinaryMask
BinaryAddress
172.16.122.204 255.255.0.0
172 16 122 204
255
Address Mask
255 0 0
Network Host
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-36
Routing TableNET INT Metric
124
S0S0E0
100
1.0 4.0
1.3E0
4.3
S0
2.2
E0
2.1
S0
4.1
4.2
1.1
1.2
Routing TableNET INT Metric
124
E0S0S0
001
• Logical addressing allows for hierarchical network• Configuration required• Uses configured information to identify paths to networks
Network Layer Functions (cont.)Network Layer Functions (cont.)
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-37
Routers: Operate at the Network Layer
Routers: Operate at the Network Layer
• Broadcast control
• Multicast control
• Optimal path determination
• Traffic management
• Logical addressing
• Connects to WAN services
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-38
Using Routers to Provide Remote Access
Using Routers to Provide Remote Access
Internet
Telecommuter
Branch Office
Modem or ISDN TA
Mobile User
Main Office
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-39
Transport Layer FunctionsTransport Layer Functions
• Distinguishes between upper layer applications
• Establishes end-to-end connectivity between applications
• Defines flow control
• Provides reliable or unreliable services for data transfer
Net
wo
rkIPXIP
Tra
nsp
ort
SPXTCP UDP
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-40
Reliable Transport Layer Functions
Reliable Transport Layer Functions
Synchronize
Acknowledge, Synchronize
Acknowledge
Data Transfer
(Send Segments)
Sender Receiver
Connection EstablishedConnection EstablishedConnection EstablishedConnection Established
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-41
Network Device DomainsNetwork Device Domains
Hub Bridge Switch Router
Collision Domains:
1 4 4 4 Broadcast Domains:
1 1 1 4
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-42
Choosing a Cisco Product Choosing a Cisco Product
Distribution Layer
Core Layer
AccessLayer
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-43
Product Selection Considerations
Product Selection Considerations
• Provides functionality and features you need today
• Capacity and performance
• Easy installation and centralized management
• Provides network resiliency
• Investment protection in existing infrastructure
• Migration path for change and growth
• Seamless access for mobile users and branch offices
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-44
• First select WAN technology solutions based on the following:
– Availability of service
– Bandwidth requirement
– Cost
• Second, choose products that support selected WAN solutions
Product Selection Considerations (cont.)
Product Selection Considerations (cont.)
Co
st
pe
r M
on
th
Usage
Leased Line, T1
Modem/ISDN
Frame Relay
0
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-45
Product Selection Considerations (cont.)
Product Selection Considerations (cont.)
1544
128
64
56
19.2
9.6
4.8
Determine applications that you want to run
ISDN, ISDN, Frame RelayFrame Relay
Old ModemOld Modem Telnet
New ModemNew ModemWeb Browsing
Voice
Video, Multimedia
E-Mail, File Transfer
Leased Line,Leased Line,Frame Relay,Frame Relay,XDSLXDSL
kbps
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-46
Selection Issues:
• Need for 10 Mbps or 100 Mbps on media
• Port density
• Need for management console
• Easy Operations
Cisco 1500Micro Hub
CiscoFastHub300
Cisco 1528Micro Hub 10/100
CiscoFastHub400
CiscoFastHub200
CiscoFastHub100
Cisco Hub ProductsCisco Hub Products
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-47
Selection Issues:
• Need for 10 Mbps, 100 Mbps, or 1000 Mbps on media
• Need for trunking and inter-switch links
• Workgroup segmentation (VLANs)
• Port density needs
• Different user interfaces
Desktop/Workgroup Solutions
Wiring Closet/Backbone
Solutions
Cisco 1548 Micro Switch 10/100
Catalyst 3000 series
Catalyst 2900series XL
Catalyst 1900/2820 series
Catalyst 2900 series
Catalyst 5000 series
Catalyst 8500 series
Catalyst Switch ProductsCatalyst Switch Products
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-49
Selection Issues:
• Scale of the routing features needed
• Port density/variety requirements
• Capacity and performance
• Common user interface
Cisco700/800Series
Cisco1600/1700
Series
Cisco2500 Series
Cisco3600 Series
AS 5000 Series
Small Office Solutions
Branch Office Solutions
Central Site Solutions
Cisco12000 GSR
Series
Cisco4000 Series
Cisco7000
Series
Home Office Solutions
Cisco2600 Series
Cisco Router ProductsCisco Router Products
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-51
Visual ObjectiveVisual Objective
Use the product selection tool to select Cisco Equipment
© 1999, Cisco Systems, Inc. www.cisco.com ICND—2-52
SummarySummary
After completing this chapter, you should be able to perform the following tasks:• Describe how data moves through a network
• Identify the roles and functions of routers, switches and hubs, and specify where each device best fits in the network
• Select the appropriate Cisco equipment for a network that combines switching, routing and remote access requirements