Transcript 2. Network Media

WXES2106
Network Technology
Semester 1 2004/2005
Chapter 2
Networking Media
CCNA1: Module 3, 4 and 5
Contents
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Introduction
Copper Media
Optical Media
Wireless Media
Cable Testing
Cabling the LAN
Cabling the WAN
Introduction
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Proper selection of cabling is key to efficient network
operation.
Copper cable is used in almost every LAN
Optical fiber is the most frequently used medium for the
longer, high bandwidth, point-to-point transmissions
required on LAN backbones and on WANs.
Different specifications for cable
 Speed of bit transmission (bps)
 Transmission type (Base or Broad)
 Maximum distance
 Example: 10BASE-T, 10BASE5, 10BASE2
Introduction
Copper Media
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Coaxial Cable
 Longer distance
 Thicknet coaxial cable more expensive to install
Copper Media
Screened UTP (ScTP)
Shielded twisted-pair cable (STP)
Copper Media
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UnShielded twisted-pair cable (STP)
 Easy to install and less expensive
 Type of connection: Straight through, Crossover,
Rollover
Copper Media
Straight through
Crossover
Rollover
Optical Media
Optical Media
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Every fiber-optic cable used for networking consists of
two glass fibers encased in separate sheaths.
One fiber carries transmitted data from device A to
device B. The second fiber carries data from device B to
device A.
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This provides a full-duplex communication link.
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Optical Media
Optical Media
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Connectors are attached to the fiber ends so that the
fibers can be connected to the ports on the transmitter
and receiver.
Subscriber Connector (SC connector) - Multimode
fiber
Straight Tip (ST) connector - Single-mode fiber
Optical Media
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Optical Receiver
 Use PIN photodiodes to detect laser/LED light
 PIN photodiodes absorb light of 850, 1310, or 1550
nm
 When detects light, produces electrical signal for
network
Installation of Fiber
 Pull fiber through interducting (stiffer piping) to reduce
bends
 Cleave (cut) & polish ends
 Attach connector
Optical Media
Wireless Media
Standard
802.11b
(Wi-Fi)
802.11a
802.11g
Max.
Typical
Bandwidth throughput
11 Mbps
54 Mbps
54 Mbps
2-4 Mbps
Freq.
Band
2.4 GHz
20-26 Mbps 5 GHz
15-26 Mbps 2.4 GHz
Wireless Media
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A wireless network may consist of as few as two devices
 Access Point
 Central hub for WLAN
 It is hard wired to the cabled LAN to provide Internet
access and connectivity to the wired network.
 Equipped with antennae and provide wireless
connectivity over a specified area referred to as a
cell.
 The range will be from 91.44 to 152.4 meters
 Wireless NIC
Wireless Media
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Wireless Connectivity
 When a client is activated within the WLAN, it will start
"listening" for a compatible device with which to
"associate".
 A probe request is sent from the wireless node
seeking to join the network.
 The probe request will contain the Service Set
Identifier (SSID) of the network it wishes to join.
 When an AP with the same SSID is found, the AP will
issue a probe response.
 The
authentication and association steps are
completed.
Wireless Media
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Authentication and Association types
 Unauthenticated and unassociated
 The node is disconnected from the network and not
associated to an access point.
 Authenticated and unassociated
 The node has been authenticated on the network
but has not yet associated with the access point.
 Authenticated and associated
 The node is connected to the network and able to
transmit and receive data through the access point.
Wireless Media
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Authentication Process
 Open System
 The SSID must match.
 Shared Key
 Requires the use of Wireless Equivalency
Protocol (WEP) encryption.
 Nodes attempting to access the network through the
AP must have a matching key.
Wireless Media
Frame Type
Adaptive Rate Selection
Wireless Media
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Wireless Security
 EAP-MD5
 Extensible Authentication Protocol
 LEAP (Cisco)
 Lightweight Extensible Authentication Protocol
 Provides security during credential exchange,
encrypts using dynamic WEP keys, and supports
mutual authentication.
 User authentication
 Encryption
 Data authentication
Cable Testing
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Inferior quality of network cabling results in network
failures and unreliable performance.
All media require testing to determine the quality.
Attenuation (signal deterioration) and noise (signal
interference) cause problems in networks because the
data is not recognizable when it is received.
Proper attachment of cable connectors and proper cable
installation are important.
Cable Testing
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Cable Testing Standard
 Wire map
 Insertion loss
 Near-end crosstalk (NEXT)
 Power sum near-end crosstalk (PSNEXT)
 Equal-level far-end crosstalk (ELFEXT)
 Power sum equal-level far-end crosstalk (PSELFEXT)
 Return loss
 Propagation delay
 Cable length
 Delay skew
Cable Testing
Cabling the LAN
Media Types Symbol
Cabling the LAN
LAN Physical Layer Implementation
Cabling the LAN
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Ethernet is the most widely used LAN technology.
An Ethernet speed of 10 Mbps can be used at the user
level to provide good performance.
Fast Ethernet can be used to connect enterprise servers.
Cabling the LAN
Ethernet Media
Cabling the LAN
Ethernet Media
Cabling the LAN
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Straight-through
 Switch to router
 Switch to PC or server
 Hub to PC or server
Crossover
 Switch to switch
 Switch to hub
 Hub to hub
 Router to router
 PC to PC
 Router to PC
Rollover
 A terminal and a console port
Cabling the LAN
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Wireless networks use radio Frequency (RF), laser,
infrared (IR), or satellite/microwaves to carry signals
from one computer to another without a permanent cable
connection.
A wireless network can be created with much less
cabling than other networks.
Cabling the LAN
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In LAN design, no more than four repeaters can be
used between hosts on a LAN. This rule is used to limit
latency added to frame travel by each.
Using a hub changes the network topology from a
linear bus, where each device plugs directly into the
wire, to a star.
Bridge break up a large LAN into smaller, more easily
managed segments.
Switch alleviates congestion in Ethernet LANs by
reducing the traffic and increasing the bandwidth. It
operates at much higher speeds than bridges and can
support new functionality, such as virtual LANs.
Cabling the LAN
Micro Segmentation of Network
Cabling the LAN
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Peer-To-Peer
 Networked computers act as equal partners, or peers.
As peers, each computer can take on the client
function or the server function.
Client/Server
 Network services are located on a dedicated
computer called a server. The server responds to the
requests of clients. The server is a central computer
that is continuously available to respond to requests
from clients
Cabling the LAN
Cabling the LAN
Cabling the WAN
WAN Physical Layer
Cabling the WAN
WAN Serial Connection
Cabling the WAN
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Routers are responsible for routing data packets from
source to destination within the LAN, and for providing
connectivity to the WAN.