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Chapter 2
Internetworking
Concepts Overview
© 2000, Cisco Systems, Inc.
2-1
Objectives
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.
© 2000, Cisco Systems, Inc.
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ICND v1.1—2-3
Defining Components
of the Network
Home
Office
Mobile
Users
Internet
Branch Office
© 2000, Cisco Systems, Inc.
Main Office
www.cisco.com
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Defining Components of
the Network (cont.)
Branch
Office
Floor 2
Server Farm
ISDN
Floor 1
Telecommuter
Remote
© 2000, Cisco Systems, Inc.
Campus
www.cisco.com
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Network Structure Defined by
Hierarchy
Core Layer
Distribution
Layer
Access
Layer
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Access Layer Characteristics
Access Layer
• End-station entry point to the network
© 2000, Cisco Systems, Inc.
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Distribution Layer
Characteristics
• Access layer
aggregation point
Distribution Layer
• Traffic routing
• Broadcast/multicast
domains
• Media translation
• Security
• Possible point for remote access
© 2000, Cisco Systems, Inc.
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Core Layer Characteristics
Core Layer
• Fast transport to enterprise services
• No packet manipulation
© 2000, Cisco Systems, Inc.
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OSI Model Overview
Application
Application
(Upper)
Layers
Presentation
Session
© 2000, Cisco Systems, Inc.
www.cisco.com
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OSI Model Overview
Application
Application
(Upper)
Layers
Presentation
Session
Transport
Network
Data-Link
Data Flow
Layers
Physical
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Role of Application Layers
Examples
Application
© 2000, Cisco Systems, Inc.
User Interface
www.cisco.com
Telnet
FTP
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Role of Application Layers
Examples
Application
Presentation
© 2000, Cisco Systems, Inc.
User Interface
Telnet
FTP
• How data is presented
• Special processing
such as encryption
ASCII
EBCDIC
JPEG
www.cisco.com
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Role of Application Layers
Examples
Application
Presentation
Session
© 2000, Cisco Systems, Inc.
User Interface
Telnet
FTP
• How data is presented
• Special processing
such as encryption
ASCII
EBCDIC
JPEG
Keeping different
applications’
data separate
Operating System/
Application Access
Scheduling
www.cisco.com
ICND v1.1—2-14
Role of Application Layers
Examples
Application
Presentation
Session
• User interface
Telnet
FTP
• How data is presented
• Special processing
such as encryption
ASCII
EBCDIC
JPEG
• Keeping different
applications’ data
separate
Operating System/
Application Access
Scheduling
Transport
Network
Data-Link
Physical
© 2000, Cisco Systems, Inc.
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ICND v1.1—2-15
Role of Data Flow Layers
Examples
Physical
© 2000, Cisco Systems, Inc.
• Move bits between devices
• Specifies voltage, wire speed, and
pin-out cables
www.cisco.com
EIA/TIA-232
V.35
ICND v1.1—2-16
Role of Data Flow Layers
Examples
Data Link
• Combines bits into bytes and
bytes into frames
• Access to media using MAC address
• Error detection not correction
Physical
• Move bits between devices
• Specifies voltage, wire speed, and
pin-out cables
© 2000, Cisco Systems, Inc.
www.cisco.com
802.3 / 802.2
HDLC
EIA/TIA-232
V.35
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Role of Data Flow Layers
Examples
Network
Provide logical addressing that
routers use for path determination
IP
IPX
Data Link
• Combines bits into bytes and
bytes into frames
• Access to media using MAC address
• Error detection not correction
802.3 / 802.2
HDLC
Physical
• Move bits between devices
• Specifies voltage, wire speed, and
pin-out cables
© 2000, Cisco Systems, Inc.
www.cisco.com
EIA/TIA-232
V.35
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Role of Data Flow Layers
Examples
• Reliable or unreliable delivery
• Error correction before retransmit
TCP
UDP
SPX
Network
Provide logical addressing that
routers use for path determination
IP
IPX
Data Link
• Combines bits into bytes and
bytes into frames
• Access to media using MAC address
• Error detection not correction
802.3 / 802.2
HDLC
Physical
• Move bits between devices
• Specifies voltage, wire speed, and
pin-out cables
Transport
© 2000, Cisco Systems, Inc.
www.cisco.com
EIA/TIA-232
V.35
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Role of Data Flow Layers
Application
Presentation
Examples
Session
Transport
• Reliable or unreliable delivery
• Error correction before retransmit
TCP
UDP
SPX
Network
• Provide logical addressing that
routers use for path determination
IP
IPX
Data-Link
• Combines bits into bytes and
bytes into frames
• Access to media using MAC address
• Error detection, not correction
802.3/802.2
HDLC
Physical
• Move bits between devices
• Specifies voltage, wire speed, and
pinout cables
© 2000, Cisco Systems, Inc.
www.cisco.com
EIA/TIA-232
V.35
ICND v1.1—2-20
Encapsulating Data
Application
Presentation
Session
Upper-Layer Data
TCP Header
Transport
Upper-Layer Data
IP Header
Data
LLC Header
Data
FCS
MAC Header
Data
FCS
0101110101001000010
© 2000, Cisco Systems, Inc.
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PDU
Segment
Network
Packet
Data-Link
Frame
Physical
Bits
ICND v1.1—2-21
De-encapsulating Data
Application
Presentation
Session
Upper-Layer Data
Transport
Upper-Layer Data
Network
TCP+ Upper-Layer Data
IP + TCP + Upper-Layer Data
Data-Link
LLC Hdr + IP + TCP + Upper-Layer Data
Physical
0101110101001000010
© 2000, Cisco Systems, Inc.
www.cisco.com
ICND v1.1—2-22
Written Exercise 1: OSI Model
OSI Model
PDU
Functional Responsibilities
Examples
Application
Presentation
Session
Transport
Network
Data-Link
Physical
© 2000, Cisco Systems, Inc.
www.cisco.com
ICND v1.1—2-23
Physical Layer Functions
Defines
• Signaling type
© 2000, Cisco Systems, Inc.
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802.3
• Connector type
Physical
• Media type
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Physical Layer: Ethernet/802.3
10Base2—Thin Ethernet
10Base5—Thick Ethernet
Host
Hub
10BaseT—Twisted Pair
Hosts
© 2000, Cisco Systems, Inc.
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Hubs Operate at Physical Layer
Physical
A
B
C
D
• All devices are in the same collision domain.
• All devices are in the same broadcast domain.
• Devices share the same bandwidth.
© 2000, Cisco Systems, Inc.
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Hubs: One Collision Domain
• More end stations means
more collisions.
• CSMA/CD is used.
© 2000, Cisco Systems, Inc.
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Data-Link Layer Functions
• Physical source and
destination addresses
• Network topology
• Frame sequencing
• Flow control
Physical
• Higher-layer protocol
(service access point)
associated with frame
Data-Link
Defines:
802.2
802.3
EIA/TIA-232
V.35
• Connection-oriented
or connectionless
© 2000, Cisco Systems, Inc.
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ICND v1.1—2-28
Data-Link Layer Functions (cont.)
MAC Layer—802.3
Number of Bytes
8
6
6
Preamble Destination Address Source Address
0000.0C
IEEE Assigned
xx.xxxx
Vendor
Assigned
2
Length
Variable
Data
4
FCS
Ethernet II
uses “Type”
here and
does not use
802.2.
MAC Address
© 2000, Cisco Systems, Inc.
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Data-Link Layer Functions (cont.)
802.2 (SNAP)
Number of Bytes
1
1
1 or 2
Destination
SAP
Source SAP
Control
AA
AA
03
OR
2
OUI
Type
ID
Variable
Data
802.2 (SAP)
1
1
1 or 2
Destination
SAP
Source
SAP
Control
Number of Bytes
Preamble
3
Destination
Address
Source
Address
Length
Variable
Data
Data
FCS
MAC Layer—802.3
© 2000, Cisco Systems, Inc.
www.cisco.com
ICND v1.1—2-30
Switches and Bridges Operate
at Data-Link Layer
Data-Link
1
2
3
4
OR
1
2
• Each segment has its own collision domain.
• All segments are in the same broadcast domain.
© 2000, Cisco Systems, Inc.
www.cisco.com
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Switches
Switch
Memory
• Each segment is its
own collision domain.
• Broadcasts are
forwarded to all
segments.
© 2000, Cisco Systems, Inc.
www.cisco.com
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Network Layer Functions
• Interconnects
multiple data links
© 2000, Cisco Systems, Inc.
Data-Link
• Defines paths
through network
IP, IPX
802.2
Physical
Network
• Defines logical
source and
destination
addresses
associated with a
specific protocol
802.3
www.cisco.com
EIA/TIA-232
V.35
ICND v1.1—2-33
Network Layer Functions (cont.)
Network Layer End-Station Packet
IP Header
Logical
Address
Source
Address
Data
172.15.1.1
Network
© 2000, Cisco Systems, Inc.
Destination
Address
Node
www.cisco.com
ICND v1.1—2-34
Network Layer Functions (cont.)
Address
Mask
172.16.122.204 255.255.0.0
172
16
122
204
Binary
Address 10101100 00010000 01111010 11001100
255
Binary
Mask
255
11111111 11111111
Network
© 2000, Cisco Systems, Inc.
www.cisco.com
0
0
00000000 00000000
Host
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Network Layer Functions (cont.)
1.0
1.1
4.0
1.3
E0
1.2
2.1
2.2
S0
S0
Routing Table
NET INT Metric
1
E0
0
2
S0
0
4
S0
1
4.3
4.1
4.2
E0
Routing Table
NET INT Metric
1
S0
1
2
S0
0
4
E0
0
• Logical addressing allows for hierarchical network.
• Configuration is required.
• Configured information identifies paths to networks.
© 2000, Cisco Systems, Inc.
www.cisco.com
ICND v1.1—2-36
Routers: Operate at the
Network Layer
• Broadcast control
• Multicast control
• Optimal path
determination
• Traffic management
• Logical addressing
• Connects to WAN
services
© 2000, Cisco Systems, Inc.
www.cisco.com
ICND v1.1—2-37
Using Routers to Provide
Remote Access
Modem or ISDN Terminal Adapter
Telecommuter
Mobile User
Branch Office
Main Office
Internet
© 2000, Cisco Systems, Inc.
www.cisco.com
ICND v1.1—2-38
Transport Layer Functions
• Defines flow control
• Provides reliable or
unreliable services for
data transfer
© 2000, Cisco Systems, Inc.
Network
• Establishes end-to-end
connectivity between
applications
Transport
• Distinguishes between
upper-layer applications
www.cisco.com
TCP
UDP
IP
SPX
IPX
ICND v1.1—2-39
Reliable Transport Layer
Functions
Sender
Receiver
Synchronize
Acknowledge, Synchronize
Acknowledge
Connection Established
Data Transfer
(Send Segments)
© 2000, Cisco Systems, Inc.
www.cisco.com
ICND v1.1—2-40
Network Device Domains
Hub
Bridge
Switch
Router
Collision Domains:
1
4
Broadcast Domains:
1
© 2000, Cisco Systems, Inc.
1
www.cisco.com
4
4
1
4
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Choosing a Cisco Product
Core Layer
Distribution
Layer
Access
Layer
© 2000, Cisco Systems, Inc.
www.cisco.com
ICND v1.1—2-42
Product Selection
Considerations
•
•
•
•
Functionality and features you need today
Capacity and performance
Easy installation and centralized management
Network resiliency
• Investment protection in existing infrastructure
• Migration path for change and growth
• Seamless access for mobile users and
branch offices
© 2000, Cisco Systems, Inc.
www.cisco.com
ICND v1.1—2-43
• First, select WAN
technology solutions
based on the following:
– Availability of service.
– Bandwidth requirement.
– Cost.
• Second, choose products
that support selected WAN
solutions.
© 2000, Cisco Systems, Inc.
www.cisco.com
Cost per
Month
Product Selection
Considerations (cont.)
Modem/ISDN
Leased Line, T1
Frame Relay
0
Usage
ICND v1.1—2-44
Product Selection
Considerations (cont.)
kbps
1544 Leased Line,
Frame Relay,
128 xDSL
64 ISDN,
Frame Relay
56
Video, Multimedia
Voice
Web Browsing
19.2 New Modem
E-Mail, File Transfer
9.6
Old Modem
Telnet
4.8
• Determine applications that you want to run.
© 2000, Cisco Systems, Inc.
www.cisco.com
ICND v1.1—2-45
Cisco Hub Products
Selection Issues:
• Need for 10 Mbps or 100 Mbps on media
• Port density
• Need for management console
Cisco
FastHub400
Cisco
FastHub300
Cisco
FastHub200
• Easy operations
Cisco
FastHub®100
Cisco 1528
Micro Hub 10/100
Cisco 1500
Micro Hub
© 2000, Cisco Systems, Inc.
www.cisco.com
ICND v1.1—2-46
Cisco Switch Products
Selection Issues:
• Need for 10 Mbps, 100 Mbps, or 1000 Mbps on
media
Catalyst
8500 Series
• Need for trunking and Inter-Switch Links
• Workgroup segmentation (VLANs)
• Port density needs
• Different user interfaces
Catalyst
5000 Series
Catalyst
2900 Series
Catalyst
3000 Series
Catalyst 2900
Series XL
Catalyst®
1900/2820 Series
Cisco 1548 Micro
Switch 10/100
© 2000, Cisco Systems, Inc.
Wiring
Closet/Backbone
Solutions
Desktop/Workgroup
Solutions
www.cisco.com
ICND v1.1—2-47
Cisco Router Products
Cisco
12000 GSR
Series
Selection Issues:
• Scale of the routing features needed
• Port density/variety requirements
• Capacity and performance
• Common user interface
Cisco
1600/1700
Cisco Series
700/800
Series
Cisco
2500
Series
Cisco
2600
Series
Cisco
3600
Series
AS
5000
Series
Cisco
4000
Series
Cisco
7000
Series
Central Site Solutions
Branch Office Solutions
Small Office Solutions
Home Office Solutions
© 2000, Cisco Systems, Inc.
www.cisco.com
ICND v1.1—2-49
Visual Objective
• Use the product selection tool to
select Cisco equipment.
© 2000, Cisco Systems, Inc.
www.cisco.com
ICND v1.1—2-51
Summary
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.
© 2000, Cisco Systems, Inc.
www.cisco.com
ICND v1.1—2-52
Review Questions
1. What are some of the advantages of
using the OSI model in a networking
environment?
2. Describe the encapsulation process.
3. How many broadcast and collision
domains are on a hub?
© 2000, Cisco Systems, Inc.
www.cisco.com
ICND v1.1—2-53