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Network topologies
Unit objective
Describe different logical and physical
network topologies
Compare and contrast different LAN
technologies
Categorize WAN technology types and
properties
Identify virtual network components
Topic A
Topic A: Network topologies
Topic B: LAN technologies
Topic C: WAN technologies
Topic D: Virtual networks
Local area networks
Located within a
confined area
Connected by
wires or radio
waves
Node: any network
device
Host: always a
computer
Can be connected
to the Internet
Requires host OS
Network topologies
Networks defined by logical and
physical topologies
Logical — The path that data takes
between nodes
Physical — The material layout of
network wiring and locations of nodes
Logical network topologies
Two basic LANs:
– Peer-to-peer
– Client/server
Extend LAN remotely:
– Virtual private network (VPN)
Peer-to-peer model
Simple file and resource sharing
Home or small office
Computers have:
– NIC for wired or wireless connections
– Client OS that supports network
connectivity; hosts can have different
OSs
Fewer than a dozen hosts
– Client OSs have connection limits
Decentralized
All hosts have equal authority
Each host controls its own resources
Individual user responsibility
Peer-to-peer authentication
User account includes
– User name
– Password
– Permissions
User account exists on single computer
Valid user credentials for computer use
User name and password for
authentication, validation, logging on
Can create additional user accounts
Can share local resources with other users
Client/server model
Servers hold data and provide services
Scales larger than peer-to-peer network
Network operating system on server
Servers manage resources
Unlimited connections
NOS provides:
– Network directory services
– Network security, monitoring, and auditing
features
– Architectural framework (APIs) to support
server-based applications
A client/server LAN
Client/server authentication
Client OS sends login information to
directory server
Directory server responsible for user
authentication
Login process — Client communicates
with NOS on server
Activity A-1
Describing network models
Star topology
Nodes connected to central network
connectivity device
Central device distributes
information packets
Single break
doesn’t affect
other nodes
If central device
fails, all
communication
fails
Bus topology
Continuous line is formed
Nodes connected to next in line
Coaxial and T-connectors
End of line uses terminating device
Terminator absorbs the data signal
Information passes through each node once
Node determines if data is addressed to it
Simple and inexpensive design
Single break in line stops all communication
Ring topology
Each node is connected to two nodes on
either side of it
All nodes form a continuous loop
Data token passes around the ring
Node can transmit data if it has the token
Mesh topology
All nodes have
independent
connections to
all other nodes
Very fault-tolerant
and scalable design
Nodes need
multiple network
cards
Complex wiring scheme
Most often wide-area
or campus links
Might not be fully meshed
Hybrid topology
Two or more types of network
topologies combined into one network
Point-to-point vs. point-to-multipoint
Point-to-point:
– Dedicated connection between two nodes
– Only those two nodes communicate over the connection
Point-to-multipoint:
– Multiple connections from single node to multiple nodes
MPLS
Multiprotocol Label Switching
Uses labels to move data
Protocol-agnostic network
Operates between OSI Layers 2 and 3
Can carry different types of traffic for both
circuit- and packet-switching clients
Provides traffic management and QoS
support
Simple traffic shaping and Layer 3 VPNs
Label Edge Routers
Assign each data packet an MPLS
header
Header contains one or more labels
called a stack
Label stack is a 32-bit field
Label contains four elements:
–
–
–
–
20-bit label value
3-bit traffic class field
1-bit bottom-of-stack flag
8-bit time-to-live (TTL) field
Activity A-2
Describing physical network topologies
Topic B
Topic A: Network topologies
Topic B: LAN technologies
Topic C: WAN technologies
Topic D: Virtual networks
Ethernet
10 Gigabit Ethernet (10GbE)
– Fastest Ethernet standard
– Data rate of 10 gigabits per second
1000-Mbps Ethernet (Gigabit Ethernet)
– Data rate of 1000 Mbps (1 gigabit per second)
– Used for large, high-speed LANs and heavy-traffic server
connections
100-Mbps Ethernet (Fast Ethernet)
– Data rate of 100 Mbps
10-Mbps Ethernet (Twisted-pair Ethernet)
– Data rate of 10 Mbps
– Became known as Ethernet IEEE 802.3
– All subsequent Ethernet architectures conform to IEEE
802.3
Ethernet media
BASE-R — Fiber optic cable
BASE-W — Wide Area Network Physical
Layer (WAN PHY)
– Fiber optic cables
– Same types of fiber and support the same
distances as 10GBASE-R
– Ethernet frames encapsulated in SONET
frames
BASE-T — STP or UTP
BASE-C — Shielded copper twisted-pair
continued
Ethernet media, continued
F typically identifies fiber optic cabling
R refers to LAN technologies
W refers to WAN encodings
S, L, and E designate wavelength
10-Gigabit Ethernet standards
Standard
Medium
Distance
10GBASE-T
Copper twistedpair, shielded or
unshielded
100 meters with
CAT6a; up to 55
meters with CAT6
10GBASE-SR,
10GBASE-SW
Multi-mode fiber
26 or 82 meters,
depending on cable
type
Notes
Preferred choice
for optical cabling
within buildings.
300 meters over 50
microns at 2000 MHz
per km with OM3
multi-mode fiber
10GBASE-LR,
10GBASE-LW
Single-mode fiber
10 km
10GBASE-ER,
10GBASE-EW
Single-mode fiber
40 km
Used to connect
transceivers.
Gigabit Ethernet standards
Standard
Medium
Distance
Notes
1000BASE-T
Unshielded twistedpair: CAT5, CAT5e,
or CAT6
100 meters per
network segment
Requires all four wire
pairs.
1000BASE-CX
Balanced copper
25 meters
shielded twisted-pair
An initial standard for
Gigabit Ethernet
connections.
1000BASE-LX
Single-mode optic
fiber
5 km*
(See the notes below this
table in course book.)
1000BASE-LX10
Single-mode optic
fiber
10 km
Wavelength of 1270 to
1355 nm.
1000BASE-BX10
Single-mode fiber,
over single-strand
fiber
10 km
Different wavelength
going in each direction—
1490 nm downstream,
1310 nm upstream.
1000BASE-SX
Multi-mode optic
fiber
500 meters
Fast Ethernet standards
Standard
Medium
Distance
Notes
100BASE-TX
Twisted-pair
copper, CAT5
or above
100 meters per
network segment
Runs over two pairs:
one pair of twisted
wires in each direction.
The most common
Fast Ethernet.
100BASE-FX
Single- or
multi-mode
fiber
400 meters for halfduplex
2 km for full-duplex
over MMF
Uses two strands: one
for receiving and one
for transmitting.
Not compatible with
10BASE-FL.
10BASE-T
10 Mbps
Copper twisted-pair cable
Up to 100 meters
Easier to install than coax Ethernet
Ethernet bonding
Combines bandwidth of two NICs
Increases bandwidth
Provides fault tolerance
Data transmission
Ethernet LANs are broadcast domains
Wire is a shared transmission system
All nodes detect the data transmission
on the network
Only the node to which the data was
addressed receives it
Data collisions
Channel access methods
Determine physical methodology by
which data is sent across transmitting
media
CSMA/CD
– Carrier sensing
– Multiple access
– Collision detection
CSMA/CA
– Avoids collisions; does not detect them
– Uses alert messages
Activity B-1
Describing Ethernet standards
Topic C
Topic A: Network topologies
Topic B: LAN technologies
Topic C: WAN technologies
Topic D: Virtual networks
Wide area networks
Span larger geographical distances
Connect multiple LANs using high-speed
communication lines
Expand beyond own premises
Typically lease data lines from public carrier
Packet vs. circuit switching
Packet switching:
– Data grouped into packets before being sent
over shared network
– Packets can contain a variety of data types
– Packets can be buffered and queued
– Can result in transmission delays
– Examples: LAN and Internet
Circuit switching:
– Dedicated path for data transmission between
two nodes
– Transfer moves at non-stop rate
– Path unavailable for other traffic until it’s
released
– Examples: PSTN and ISDN
WAN connections
WAN connection
Description
Dial-up networking
(DUN)
Uses a modem to connect through regular analog
phone lines.
Digital Subscriber Line
(DSL)
High-speed connections made over regular analog
phone lines.
Cable
Connections made over the same lines that carry
cable television signals.
Satellite
Connections made by sending signals to and
receiving signals from satellites in orbit around the
earth.
Wireless
Connections made through infrared light or radio
waves. Wireless connections can also be made over
cellular telephone networks or via satellite.
Cellular
Connections made through a cell phone or laptop’s
cellular network PC Card on a cellular phone network.
continued
WAN connections, continued
Used to connect:
– Small ISP or large business to regional
ISP
– Regional ISP to an Internet backbone
T lines and E lines
X.25 and frame relay
ATM
POTS/PSTN
Dial-up system over telephone lines
Connection isn’t continuous
Phone and data share line; only one can be used at
a time
Max data speed 56 Kbps
Modem bonding combines speed of multiple
modems
ISDN
Uses phone lines
– 2 data channels
– Control signal channel
Data not converted to analog
Terminal adapter
Each data channel can transmit data at up
to 64 Kbps
Two channels can be combined to move
data at speed of 128 Kbps
Basic Rate Interface (BRI)
PRI: 23 channels + control channel
DSL
High-speed data and voice
transmission line
Uses telephone wires for data
transmission
Carries digital data at frequencies
above voice transmission
Can transmit voice and digital data on
same line at same time
Typical speeds: 1.5 Mbps in both
directions
continued
DSL, continued
ADSL — Up to 640 Kbps upstream
and 7.1 Mbps downstream
SDSL — Up to 1.544 Mbps
HDSL — Up to 1.5 Mbps
VDSL — Up to 52 Mbps downstream
and 16 Mbps upstream
DSL Lite or G.Lite — Up to 384 Kbps
upstream and 6 Mbps downstream
Can bond multiple DSL lines for higher
bandwidth
Cable
Uses transceiver (cable modem) to send and
receive data
Uses same line as cable TV
Different frequencies
Speed examples: 500 Kbps up to 10 Mbps
Optional VoIP
Satellite
Useful in rural areas
Uses dish mounted on building to communicate
with stationary satellite in orbit
Downlink uses satellite (up to 1.5 Mbps)
Uplink sometimes dial-up
Wireless
Technologies that don’t use cables
Public radio, cell phones, one-way paging, satellite,
infrared, and private, proprietary radio
More expensive to install and use
Health concerns; wireless network can interfere
with other devices
Two types: fixed-point wireless and mobile wireless
WiMAX
802.16 Air Interface Standard
Worldwide Interoperability of Microwave
Access
Provides DSL and T1-level service
Point-to-multipoint broadband wireless
access standard
Used for WANs and MANs
10–66 GHz licensed; 2–11 GHz unlicensed
70 Mbps
Max of 31 miles
Doesn’t require a line of sight
Cellular
Provided by major cell phone companies
Access via cell signal with Internet-capable
phone or laptop using cellular network PC
card
Faster than dial-up; slower than DSL or
cable
T and E lines
First digitized voice transmission
Work with leased digital
communications line
Transmit both voice and data
T1
– 24 channels
– 64 Kbps each
– Total of 1.544 Mbps
T3
– 672 channels
– Total of 44.736 Mbps
continued
T and E lines, continued
E carrier: European equivalent of T
line
– E1: 2.048 Mbps
– E3: 34.368 Mbps
T and E use 4 wires: 2 for receiving
and 2 for sending
Fiber optic and STP preferred over
coaxial
Repeaters every 6000 ft.
continued
T and E lines, continued
Business lines
– T1: coaxial, microwave, or fiber optic
– T3: microwave or fiber optic
Can lease fractional line
– T1: 64 Kbps increments
– T3: 1.544 Mbps increments
D3 (Digital Signal 3): Digital T3 or E3
line
X.25 and frame relay
Packet-switching communication
protocols
Designed for long-distance data
transmission
Packet-switching technology
–
–
–
–
Divides data into packets
Sends each packet separately
Used on Internet
Uses bandwidth efficiently
continued
X.25 and frame relay, continued
Frame relay
– Digital
– T1 or T3 lines
– Speeds from 64 Kbps to 44.736 Mbps
X.25
– Analog
– Up to 56 Kbps
Both use a permanent virtual circuit
(PVC)
continued
X.25 and frame relay, continued
PVCs aren’t dedicated lines
– You specify
Nodes (two endpoints)
Amount of bandwidth required
– Carrier sends data along any number of
paths between the two endpoints
Advantage: pay for only the amount of
bandwidth you need
International businesses use frame
relay
ATM
Very fast network technology
Used with LANs and WANs
Uses cells to transmit data, voice, video,
and frame relay traffic
Each cell is 53 bytes
– 48 bytes of data
– 5-byte header
Uses virtual circuits
– PVCs
– SVCs
Throughput of 622 Mbps
Best with fiber optic cable; can use TP
SONET and SDH
Synchronous Optical Network
ANSI standard for signal transmission on
optical networks
Signal Digital Hierarchy: European
counterpart to SONET
Categories: Signal
Rate
STS-1, OC-1
51.8 Mbps
STS-3, OC-3
155.5 Mbps
STS-12, OC-12
622.0 Mbps
STS-48, OC-48
2.48 Gbps
STS-192, OC-192
9.95 Gbps
STS-768, OC-768
39.81 Gbps
DWDM
Dense wavelength division
multiplexing
Increases data capacity of fiber
networks such as SONET and SDM
Assigns optical signals to specific
frequencies of light within a band
Can carry multiple protocols without a
common signal format
PON
Passive optical network
Shared point-to-multipoint fiber
network
continued
PON, continued
Activity C-1
Discussing WAN bandwidth technologies
Topic D
Topic A: Network topologies
Topic B: LAN technologies
Topic C: WAN technologies
Topic D: Virtual networks
Virtual computers
Virtual applications
Virtual desktops
Virtual servers
Virtual PBX
Virtualization concerns and risks
Compliance with security standards
Rogue VMs
Orphaned VMs
Legal and regulatory compliance
Activity D-1
Exploring the benefits and risks of
virtualization
Cloud computing
Key features
–
–
–
–
–
–
Elastic provisioning
Cost benefits
Standardized API
Simplified installation
Multi-tenancy
Reliability and redundancy
Cloud deployment
Public cloud
Private cloud
Mixed cloud
Cloud categories
Software as a Service
Platform as a Service
Infrastructure as a Service
Risks and concerns
Data residing outside your network
Privacy and data loss
Compliance with laws and regulations
Intellectual property agreements
Activity D-2
Exploring the benefits and risks of
cloud computing
Unit summary
Described different logical and
physical network topologies
Compared and contrasted different
LAN technologies
Categorized WAN technology types
and properties
Identified virtual network components