Chapter 2
Review of Computer Network
Technology
Outline
1.
2.
3.
4.
Network Topology
Local Area Networks
Network Node Components
Internet TCP/IP Protocols
 Refer to net-inrtro.ppt
5. Transmission Technology
1. Network Topology
- LAN Topology
DTE
DTE
DTE
DTE
DTE
Ethernet
DTE
DTE
Bus
DTE
DTE
DTE
Star
DTE
Figure 2.1(c) Star Topology
Figure 2.1(a) Bus Topology
DTE
DTE
DTE
DTE
DTE
Ring
DTE
DTE
DTE
DTE
DTE
DTE
DTE
Ethernet Hub
Token Ring Hub
Figure 2.1(b) Ring Topology
Figure 2.1(d) Hub Configurations
A Campus Network
Of LANs
10.1.1.2
10.1.1.3
10.1.1.4
10.1.1.5
Ethernet 10.1.1.0
10.1.1.1
Bridge
10.1.2.6
Ethernet 10.1.2.0
10.1.2.2
10.1.2.3
10.1.2.4
10.1.2.5
FDDI Ring
10.10.0.0
External
Network
Router
Router
Half-Router
Router
Half-Router
Ethernet 10.3.1.0
10.1.2.1
Router
ATM ELAN 10.4.1.0
Token-ring
10.2.1.0
1. Network Topology
- WAN Topology
N1
N2
N1
N3
N5
N2
N6
N3
N4
N4
N5
N6
Figure 2.2(a) Mesh Topology
Mesh
Tree
Figure 2.2(b) Tree Topology
2. Local Area Network

Type of LANs
 Ethernet
 Fast Ethernet
 Gigabit Ethernet
 Half-duplex Vs Full-duplex
 Switched Ethernet
 VLAN (Virtual LAN)
 Token Ring
 FDDI
Ethernet
• IEEE 802.3 standard
• 10 Mbps data rate
• CSMA/CD
• Carrier Sense Multiple Access with Collision
Detection
• Analogy of a hollow pipe
• Back Off Algorithm
• Packet Size: 64 ~ 1500 bytes
• Segment length and drop cable length
Ethernet
Table 2.1 Ethernet LAN Topology Limits
TYPE
DESCRIPTION
SEGMENT LENGTH
DROP CABLE
10Base2
Thin coax (0.25”)
200 meters
Not allowed
10Base5
Thick Coax (0.5”)
500 meters
Twisted pair: 50 meters
10Base-T
Hub topology
N/A
Twisted pair: 100
meters
10Base-F
Hub topology
N/A
2 km
10Base-T :
10 Mbps, Baseband, Twisted Pair
Fast Ethernet
Network
Data Link
LLC
MAC Sublayer
Physical
Convergence Layer
PMD Sublayer
LLC Logical Link control
MAC Medium Access Control
PMD Physical Medium Dependent
Figure 2.4 100Base-T Fast Ethernet Protocol Architecture
LAN - IEEE 802.x
Network
802.1 (HLI)
802.5
802.4
Physical
MAC
802.2
802.3
Data Link
LLC
802.1: HLI
HLI: High Level Interface
802.2: LLC
LLC: Logical Link Control
802.3: Ethernet
MAC: Medium Access Control
802.4: Token Bus
802.5: Token Ring
Fast Ethernet




100 Mbps
100Base-T
PMD (Physical Medium Dependent)
sublayer – to be consistent with IEEE
802.3
UTP Category 5
Gigabit Ethernet



IEEE 802.3z
1 Gbps
Packet size: 512 bytes
Table 2.2 Gigabit Ethernet Topology Limits
9
micron
SingleMode
50
micron
Single
Mode
50 micron
Multimode
62.5
Balance
micron
Shielded
Multimode
Cable
UTP
1000BASE-LX
10 km
3 km
550 m
440 m
-
-
1000BASE-SX
-
550 m
260 m
-
-
1000BASE-CX
-
-
-
25 m
-
1000BASE-T
-
-
-
-
100 m
Full-Duplex Ethernet





Half-Duplex  Full-Duplex
Coaxial Cables can not support full-duplex.
UTP + Hub with full-duplex support
10Base-T, 100Base-T, 100Base-F
↓
10Base-Tx, 100Base-Tx, 100Base-Fx
Switched Ethernet
DTE
DTE
DTE
Switched Hub
= Multi-Port Bridge
DTE
Switched
hub
DTE
DTE
DTE
DTE
Virtual LAN
DTE 1
DTE 2
Router
DTE 3
Switched Hub
Port for Subnets
200.100.150.1
&
200.100.160.1
DTE 4
VLAN
VLAN
200.100.150.1 200.100.160.1
Figure 2.10 Virtual LANs
DTE 5
Advantages of VLAN





Performance
Formation of Virtual Workgroups
Simplified Administration
Reduced Cost
Security
Token Ring
DTE 4
IEEE 802.5
3 to 1 ACK
DTE 1
DTE 1 has
token control
Token
Ring
DTE 3
1 to 3 MSG
DTE 2
Figure 2.11 Token Ring LAN
Dual Ring TR LAN
DTE 4
DTE 1
Redundant
Ring
Primary
Ring
DTE 3
DTE 2
Figure 2.12(a) Token Ring Dual Ring Management
Failure Recovery in TR LAN
DTE 4
DTE 4
DTE 1
DTE 3
DTE 1
DTE 3
Failed Station
DTE 2
Figure 2.12(b) Token Ring DTE Isolation
DTE 2
Figure 2.12(c) Token Ring Segment Isolation
FDDI
•
•
•
•
•
Fiber Distributed Date Interface
Uses fiber optics medium
Modified token ring protocol
Data rate 100 Mbps
Up to 500 DTEs in a single segments of 100 km
without repeaters
• Ideal for campus backbone network
• Single and dual attached stations (SAS and DAS)
• Dual attached stations load share the two rings
Dual Ring FDDI Network
DAS
SAS
SAS
DAS
SAS Single Attached Station
DAS Dual Attached Station
Figure 2.13(a) Dual Ring FDDI Network Configuration
LAN Data Rate Race
E’Net
10Mbps
FDDI
100 Mbps
Fast E’Net
100Mbps
ATM
155.52 Mbps
Gbit E’Net
1 Gbps
Duplex
E’nets
ATM
OC-n
3. Network Node Components
•
•
•
•
•
•
•
Hubs
Bridges
Remote bridges
Routers
Gateways
Half bridge / half router
Switches
Basic Network Nodes
ATM
Switch
ATM
ATM Switch
Figure 2.14(a) Switch
Local LAN
Ethernet
Packets
Bridge
Routing
Filter
Bridge
External LAN
Ethernet
Packets
Figure 2.14(b) Bridge
Router
Local Network
IP Packets
Routing
Filter
External Network
IP Packets
Router
Figure 2.14(c) Router
Gateway
IP
Network
Packets
Format
change
Gateway
X.25
Network
Packets
Networked Components
Dial-up
Network
Half
Router
Router
Switched
Hub
External
Network
Gateway
ATM
Switch
Hub
Bridge
External
Network
Remote
Bridge
Workstation
Hub
Figure 2.15 Networked Components
Router
Hub
Hubs
• Hub is a platform with multiple ports
• Function dependent on what is housed
• LAN  multi-port repeater
• Switched LAN  bridge (switched hub)
DTE
DTE
DTE
DTE
Patch Panel
Hub
Wiring Closet
Hub 1
Backplane
Interconnection
Hub 2
Figure 2.16(b) Stacked Hub
To DTEs
Stacked Hub
Bridges
Bridge
Local Bridge
Remote Bridge
Simple
Multiport
Multiport
Multi-protocol
Refer to Figure 2.17, page 77
Bridges




Operates at Layer 2, the data link layer.
Allows networks with different physical signaling, but
with compatible data link addressing schemes, to
communicate.
Helps reduce traffic on a backbone LAN by filtering
any information coming from one segment to another
that does not need to be forwarded through the
backbone.
A common use for a bridge is to allow users on an
Ethernet LAN and a Token Ring LAN to communicate
with each other.
Bridges

Remote Bridges


Used to connect remote LANs
Transparent Bridges


Used to connect LANs of the same types
Use a Spanning Tree Algorithm for routing



Backward learning
Routing Table of ports associated with destination addresses
Source Routing Bridges


Used to network token-ring LANs
Source is aware of the entire path to the destination.
Routers
• Routers operate at network layer
• Routes packets between nodes of similar
network protocols
• Routing table used to route packets
• DLC and Physical layers could be different
under the same common network layer protocol
A Router Configuration
Network A
Protocol P
Network B
Protocol P
Router
Router
Protocol interface
TP
TP
NP
NP
NP
NP
DP
DP
DP'
DP'
Phy
Phy
Phy'
Phy'
Physical medium A
Physical medium B
Figure 2.21 Router Configuration
Gateway
• Gateway is router connecting two networks with
dissimilar network protocols
• Gateway does the protocol conversion at the
network layer
Protocol Converter
• Protocol converter does the conversion at the
application layer
Gateway Configuration
Network A
Protocol P
Network B
Protocol Q
Gateway
Gateway
TP
Protocol interface
TP
NP
NP
NP'
NP'
DP
DP
DP'
DP'
Phy
Phy
Phy'
Phy'
Physical medium
Figure 2.22 Gateway Configuration
Tunneling
Using Multiprotocol Routers
• Tunneling is transmission of packets (via
multiprotocol routers) by encapsulation
• In Figure 2.24, packets are encapsulated and
transmitted through X.25 network in a serial
mode
IP
Tunnel
Multiprotocol
Router
IP
Multiprotocol
Router
Figure 2.24 Tunneling Using Multiprotocol Routers
Ethernet
Ethernet
X.25
Half-Bridge/Half-Router
•Half-bridge (half-router) is point-to-point communication
• Uses PPP protocol
• Helps low-end users to communicate with ISP
on dial-up link saving the expense of dedicated link
Serial
Output
Router
PPP/MP
Bridge
Ethernet
• Router encapsulates packets in PPP frames and
puts serial outputs to the bridge, and vice-versa
Switches
• Switches are embedded in bridges and routers
• Switched network used in WAN
• Two types of switched networks
• Circuit-switched
• Packet-switched
• Datagram service
• Virtual circuit
Pkt3 Pkt2
Pkt1
DTE A
Pkt1
Pkt3
Pkt2
B
Pkt2
A
Pkt3
Pkt1
Pkt2
D
DTE Z
Pkt2
C
Figure 2.26(a) Datagram Configuration
Pkt1
Pkt3
Pkt2
DTE A
Pkt2
Pkt1
Pkt3
B
A
Pkt3
D
C
Figure 2.26(b) Virtual Circuit Configuration
Pkt2
Pkt1
DTE Z
5. Transmission Technology
Transmission Technology
Medium
Wired
LAN
WAN
Mode
Wireless
LAN Mobile
Digital
Satellite
Analog
Transmission Media
Media
Wireline
Transmission
Electric
Conductors
Twisted
Pair
• UTP
• STP
Coaxial
Cable
• Thin
• Thick
Wireless
Transmission
Optical
Fiber
Mono-mode
Radio
Multi-mode
Laser Links
Infrared
Microwave
Satellite
Transmission
TDM
Channel
Time
Division
Multiplexing
(TDM)
channel 24
Time
Bandwidth
Transmission Modes
channel 1
channel 2
User 24
User 1
User 2
User 3
User 4
Time
Packet
Multiplexing
Packet
Multiplexing
Bandwidth
Figure 2.27(a) T1 Time Division Multiplexing (TDM) Transmission
User 1
User 2
User 3
User 4
User 5
Time
Figure 2.27(c) Cell Transmission (ATM)
1
4
Time
U
se
r
U
se
r
1
5
U
se
r
3
5
2
r1
U
se
U
se
r
U
se
r
4
3
r1
U
se
U
se
r
U
se
r
1
Cell
Multiplexing
U
se
r
Cell
Multiplexing
Bandwidth
Figure 2.27(b) Packet Transmission ( X.25)