Network Components
 Two
basic components to the BN
 hardware
devices that connect the networks to the
backbone
hubs
 bridges
 switches
 routers
 brouters
 gateways

 network
Chapter 8
cable
4/13/2015
1
Hubs
 very
simple devices that pass all traffic in both
directions between the LAN sections they link
 same or different cable types
 use physical layer protocols
 pass on every message
 used to connect LANs of similar technology, or to
extend the distance of one LAN
 can be called repeaters or amplifiers
Chapter 8
4/13/2015
2
HUB Devices
Repeater/Amplifier
HUB (MAU)
Chapter 8
4/13/2015
3
Hubs
 inexpensive
 easy
to Install
 can connect different media
 very little delay
 limited
distance between devices
 limited on the number of repeaters
 no protocol or rate conversion
 no error detection
 does not filter
Chapter 8
4/13/2015
4
Bridges
 connect
two LAN segments that use the same data
link and network protocol
 operated at the data link layer
 same or different cable types
 forward only those messages that need to go out
(filtering)
 “learn” whether to forward packets
 internal routing table
 combination of “black box” hardware and software
Chapter 8
4/13/2015
5
Bridges
There are three types of bridges:
 Simple bridge
 Learning bridge
 Multiport bridge
Chapter 8
4/13/2015
6
Bridges Interconnecting
Bridge
Repeater/
Amplifier
Repeater/
Amplifier
HUB (MAU)
HUB (MAU)
Chapter 8
4/13/2015
7
Bridges
 may
be different data rates and different media easy
to Install
 no modifications required to the communications
software
 can learn the ports for data transmission
 understand
only data link layer protocols and
addresses
 no protocol conversion
 broadcasts when it does not know the address
Chapter 8
4/13/2015
8
Switches
 connect
more than two LAN segments that use
the same data link and network protocol.
 operate at the data link layer
 same or different type cable
 ports are usually provided for 4, 8, 16, or 32 LAN
segments
 ports are used simultaneously
 connect lower speed segments to high speed BN
Chapter 8
4/13/2015
9
Switches
 Cut-through
switches
 use
circuit-switching to immediately connect the port
with the incoming message to the correct outgoing
port
 very fast as decisions are done in hardware
 outgoing packet is lost if port is in use
 Store-and-forward
switches
 copy
the incoming packet to memory prior to
processing the destination address -- transmit it when
the outgoing port is ready
Chapter 8
4/13/2015
10
Switches Interconnecting
Wing A
Wing B
First Floor Switch
Chapter 8
Wing C
4/13/2015
Wing C
11
Switches
 much
more sophisticated than previously
 enable all ports to work at the same time
 can convert protocols
 configurable
 high speed
 understand
only data link layer protocols and
addresses
 much more expensive then previous options
 higher maintenance
Chapter 8
4/13/2015
12
Routers
 connect
two or more LANs that use the same or
different data link protocols, but the same network
protocol.
 same or different cable types
 operate at the network layer
 forward only messages that need to go out
 routers use the internetwork address
 internal routing tables
 only processes messages addressed to it
Chapter 8
4/13/2015
13
Routers
 choose
the best route to send the packet (path)
 IDs
of other networks
 paths to the networks
 relative efficiency of the paths
Chapter 8
4/13/2015
14
Routers
 The
router must deal with network differences:
 addressing
schemes
 minimum packet size
 interfaces
 reliability
Chapter 8
4/13/2015
15
Routers Interconnecting
Router
\
X.25 Network
the “cloud”
Chapter 8
Token Ring
LAN1
4/13/2015
Ethernet
LAN2
16
Routers
 can
mix-in-match protocols and convert them
 enable all ports to work at the same time
 can be used as an extra layer of security
 configurable
 high speed
 hard
to configure and manage
 access lists must be kept current
 high maintenance/high training costs
 very expensive
Chapter 8
4/13/2015
17
Brouters
 devices
that combine the functions of both bridges
and routers
 operate at both the data link and network layers
 same or different data link protocol
 same network protocol
 as fast as bridges for same data link type networks
Chapter 8
4/13/2015
18
Gateways
 complex
machines that are interfaces between two or
more dissimilar networks
 connect two or more LANs that use the same or
different data link layer, network layer, and cable types
 operates at the network layer (3) or higher layers (4-7)
 forwards only those messages that need to go out
 a combination of both hardware and software
Chapter 8
4/13/2015
19
Gateways
 translates
one network protocol to another
 translates data formats
 translates open sessions between application
programs
 translates to mainframes
Chapter 8
4/13/2015
20
Gateways
 Exists
in four major types:
 LAN-to-IBM
mainframe
 Network-to-network
 System-to-network
 System-to-system
Chapter 8
4/13/2015
21
LAN-to-IBM Mainframe
 Allow
LANs using TCP/IP and Ethernet to be
connected to IBM mainframe using SNA
 Eliminates the need for each PC on the LAN to
have SNA hardware/software that makes it act
like an IBM 3270 terminal
Mainframe
Chapter 8
Gateway
4/13/2015
22
Network-to-Network
X.75 Gateway
X.25 \Network
A
X.25 Network
\
B
X.75 provides terminal
address translation
Chapter 8
4/13/2015
23
System-to-Network
Gateway
X.25 \Network
Minicomputer or
Microcomputer
Chapter 8
4/13/2015
24
System-to-System
 allows
connecting one vendor’s architecture to
another vendor’s architecture
 allows both the existence of OSI-based and
proprietary architectures (like SNA or AppleTalk)
 gives management to tools necessary to plan a
gradual migration to a completely OSI environment
 applications can work with other application
Chapter 8
4/13/2015
25
System-to-System
Profs E-mail Gateway
\
X.25 Network
LAN E-mail Server
Profs E-mail
LAN E-mail Gateway
Chapter 8
4/13/2015
26
Backbone Network Devices
Physical Data Link Network
Layer
Layer Layer
Device
Operates at
Messages
Hub
Bridge
Physical
Data link
S/D
S/D
Same Same
Same Same
Switch
Data link
S/D
Same Same
Router
Network
S/D
S/D
Same
Brouter
Data link &
Network
Network
All transferred
Filtered using
data link layer add.
Switched using
data link layer add.
Routed using
network layer add.
Filtered & routed
S/D
S/D
Same
Routed using
network layer add.
S/D
S/D
S/D
Gateway
Chapter 8
4/13/2015
27
Terminology Warnings
 Multiprotocol
bridges translate between different data
link layer protocols.
 Multiprotocol routers translate between different
network layer protocols.
 Protocol filtering bridges forward only packets of a
certain type, i.e., token-ring or ethernet
 Encapsulating bridges connect networks with different
data link protocols, encapsulating messages with
correct protocol for transmission
 Layer-3 switches (IP switches) - can also switch
messages based on their network layer address
Chapter 8
4/13/2015
28
Shared Media Technologies
 Fast
Ethernet
 Fast Token Ring
 Fiber Distributed Data Interface
Chapter 8
4/13/2015
29
Fast Ethernet
 100Base-X
Ethernet
 100VG-AnyLAN
 Gigabit Ethernet
 Iso-ENET (isochronous ethernet)
Chapter 8
4/13/2015
30
100Base-X Ethernet
 IEEE
802.13
 identical to 10Base-T Ethernet
 three data link layer protocols
 100 Mbps data rate
 standard ethernet bus topology
 ethernet data link packets
 ethernet CSMA/CD media access protocol
Chapter 8
4/13/2015
31
100Base-X Ethernet
Three versions of 100Base-X Ethernet
 100Base-TX
 100Base-FX
 100Base-T4
Chapter 8
4/13/2015
32
100VG-AnyLAN
 IEEE
802.12
 both Ethernet or token-ring
 Demand Priority Access Method (DPAM)
polling
 polls
each computer to see if it has data to send
 can use a priority system (notification system)
 four
sets of twisted pair running at 25 Mbps
 faster than 100Base-T
Chapter 8
4/13/2015
33
Gigabit Ethernet
 IEEE
802.3Z
 1000Base-X
 1000 Mbps (1000 Mbps = 1 Gbps)
 high speed of transmission may cause
collisions to go undetected
 mainly used for point-to-point full-duplex
communication links (BN, MAN)
 PCs send or receive data at rates up to 100
Mbps
Chapter 8
4/13/2015
34
Gigabit Ethernet
Four versions of 1000Base-X Ethernet
 1000
Base-LX (fiber up to 440 meters)
 1000 Base-SX (fiber up to 260 meters)
 1000 Base-T (four pairs twisted-pair up to 100
meters)
 1000 Base-CX (one cat 5 cable up to 24 meters)
Chapter 8
4/13/2015
35
Iso-ENET
 IEEE
802.9A
 isochronous Ethernet
 standard 10Base-T Ethernet + 6.144 Mbps
 both transmitted on the same twisted pair
 6.144 circuit configured for ISDN for
transmission of voice and video
 mainly used for desktop videoconferencing
and multimedia products
Chapter 8
4/13/2015
36
Improving Circuit Capacity
How much bandwidth to expect
LAN Type
Ethernet
Token Ring
Fast Ethernet
Faster Ethernet
Fast Token Ring
FDDI
ATM
Chapter 8
Speed
10 Mbps
16 Mbps
100 Mbps
1 Gbps
100 Mbps
100 Mbps
2.4 Gbps
4/13/2015
37
Selecting a Backbone Network
5 important factors to consider:
 Throughput
 Network cost
 Type of application
 Ease of network management
 Compatibility with current and future
technologies
Chapter 8
4/13/2015
38