Transcript ch 10 Network Access and Transmission Methods

Network Access and
Transmission Methods
Chapter 10
Objectives
In this chapter, you will learn to:
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Recognize simple and complex physical topologies used
in data networks
Describe Ethernet and the CSMA/CD network access
method
Understand the different types of Ethernet access
methods
Describe the techniques used in the Token Ring, ATM,
and FDDI network access methods
Identify the main characteristics of network transmission
methods, such as X.25, Frame Relay, T-Carriers, ISDN,
DSL, cable, and SONET
Bus
Ring
Star
Hybrid Physical Topologies
Hybrid Physical Topologies
Mesh Topologies
Mesh Topologies
Network Access Methods
Ethernet
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A network access method originally developed
by Xerox in the 1970s and later improved by
Xerox, Digital Equipment Corporation (DEC),
and Intel.
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Can run on a variety of network media,
including both wireline and wireless
channels
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Uses packet switching
Ethernet
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Baseband -
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Multiple Access - refers to the fact that Ethernet
a transmission form in which digital
signals are sent through direct current (DC) pulses
applied to the wire.
nodes can be connected to a network and can
monitor and issue traffic.
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CSMA/CD - Rules for communication used by
shared Ethernet networks.
Ethernet
Ethernet
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Ethernet Frames - each frame contains a
14-byte header and a 4-byte frame check
sequence (FCS) field.
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10BaseT - a physical layer standard for
networks that use baseband transmission and
twisted pair media and can achieve 10 Mbps
throughput.
Ethernet
Ethernet
Ethernet
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10BaseF - a physical layer standard for networks that use
baseband transmission.
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100BaseT - uses baseband transmission and multimode fiber
cabling and can achieve 100 Mbps throughput.
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100BaseF - specifies a network capable of 100 Mbps
throughput that uses baseband transmission and fiber optic
cabling.
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Switched Ethernet - enables multiple nodes to
simultaneously transmit and receive data over different network
segments.
Ethernet
Token Ring
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Transmits at either 4, 16, or 100 Mbps over
STP or UTP.
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Uses the token-passing routine and a starring hybrid physical topology.
High Speed Token Ring (HSTR) - can use
either twisted pair or fiber cable as its
transmission medium.
FDDI
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A network access method whose standard was
originally specified by ANSI in the mid-1980s
and later refined by ISO.
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Uses a double ring of multimode or single mode
fiber to transmit data speeds of up to 100 Mbps.
FDDI
ATM
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Asynchronous Transfer Mode (ATM) a standard that describes both a network
access method and a multiplexing technique.
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Cells - consist of 48 bytes of data plus a fivebyte header for a 53-byte packet.
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Virtual circuits - logical connections
between network nodes.
ATM
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Quality of Service (QoS) - a standard that
specifies that data will be delivered within a
certain time period after its transmission.
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Compatibility - ATM cells can support
multiple types of higher-layer protocols,
including TCP/IP and IPX/SPX.
Network Transmission Methods
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X.25 and Frame Relay - a set of protocols
designed for long-distance data transmission
and standardized by the ITU in the mid-1970s.
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Frame Relay - an updated, digital version of
X.25 that also relies on packet switching. It
does not guarantee the delivery of data.
Network Transmission Methods
ISDN
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An international standard, established by the ITU for
transmitting data over digital lines.
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All ISDN connections are based on two types of
channels:
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B Channels: employ circuit-switching techniques to carry
voice, video and other types of data over the ISDN
connection.
D Channels: employ packet switching techniques to carry
information about the call, such as session initiation and
termination signals, caller identity, call forwarding, and
conference calling signals.
Basic Rate Interface
Primary Rate Interface
T-Carrier Services
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The general name for a group of transmission
methods that includes T1s, fractional T1s, and
T3s.
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T-carriers are examples of dedicated leased
lines.
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They are also private lines.
Types of T-Carriers
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Signal level - the T-carrier’s Physical layer
electrical signaling characteristics as defined by
ANSI standards in the early 1980s.
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T1 Circuit - can carry the equivalent of 672
voice or data channels, giving a maximum data
throughput of 44.736 Mbps.
Types of T-Carriers
T-Carrier Connectivity
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Transmission Media - T1 technology can
use unshielded or shielded twisted-pair copper
wiring.
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CSU/DSU (Channel Service Unit/Data
Service Unit) - the connection point for a Tcarrier line at the customer’s site.
• CSU: provides termination monitoring.
• DSU: converts the digital signals used by bridges,
routers and multiplexers into the digital signal sent via
the cabling.
T-Carrier Connectivity
Multiplexers
Multiplexers
DACS
DSL
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Uses advanced data modulation techniques to achieve
extraordinary throughput over regular phone lines.
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Downstream - data traveling from the
telecommunications carrier’s end office.
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Upstream - data traveling from the customer to the
carrier’s end office.
Types of DSL
 Asymmetrical: downstream throughput is usually
much higher than upstream throughput.
 Symmetrical - provides equal capacity for data
traveling both upstream and downstream.
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DSL
DSL Connectivity
DSL Connectivity
Cable Modem Technology
SONET and SDH
SONET and SDH
Summary
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Three simple physical topologies exist: bus, star, and ring.
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Ethernet is a network access method that uses Carrier Sense
Multiple Access with Collision Detection (CSMA/CD) to
determine how multiple nodes share a single channel.
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Token Ring is a network access method originally designed by
IBM and now specified by IEEE in its 802.5 project.
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Digital subscriber line (DSL) is a transmission method that uses
advanced data modulation techniques to achieve extraordinary
throughput over regular phone lines. It comes in several different
varieties.