3.4 Categorize WAN technology types
The transmission speed of a T1 circuit (Used mainly
in North America) is 1.544Mbps
The transmission speed of an E1 circuit (Used mainly
in Europe) is 2.048Mbps.
The transmission speed of a T3 circuit (Used mainly
in North America) is 44.736 mbps
OC stands for Optical Carrier and is used to specify
the speed of fiber optic networks conforming to the
SONET standard. Below are the speeds for some common
OC level Speed
OC-1 = 51.85 Mbps
OC-3 = 155.52 Mbps
OC-12 = 622.08 Mbps
OC-24 = 1.244 Gbps
OC-48 = 2.488 Gbps
OC-192 = 9.952 Gbps
DSL: DSL uses existing copper telephone lines. DSL
technologies typically provide speeds up to 1.544 Mbps.
Cable modem: Cable modem uses the same line as cable
TV. Possible bandwidth for Internet access reaches up
to 27 Mbps.
ISDN: ISDN comes in two flavors- BRI and PRI. The
most commonly used is BRI, Basic Rate Interface. BRI
is composed of two 64-Kbps B (bearer) channels and one
16 Kbps D (delta) channel. ISDN supports both voice
ISDN specifies two standard access methods:
1. BRI (Basic Rate Interface): Consists of two B
channels (64Kbps) and one D channel (16Kbps).
The B channels can be used for digitized speech
transmission or for relatively high-speed data transport.
The D channel carries signaling information (call
setup) to control calls on B channels at the UNI
2. PRI (Primary Rate Interface): Consists of 23 B
channels and one D channel with a bandwidth of 1.544Mbps.
PRI uses a DSU/CSU for a T1 connection. B stands for
WiMAX is a short name for Worldwide Interoperability
of Microwave Access. WiMAX is described in IEEE 802.16
Wireless Metropolitan Area Network (MAN) standard. It
is expected that WiMAX compliant systems will provide
fixed wireless alternative to conventional DSL and Cable
Internet. Typically, a WiMAX system consists of two
1. A WiMAX Base Station:Base station consists
of indoor electronics and a WiMAX tower. Typically,
a base station can cover up to 10 km radius (Theoretically,
a base station can cover up to 50 kilo meter radius
or 30 miles, however practical considerations limit
it to about 10 km or 6 miles). Any wireless node
within the coverage area would be able to access
2. A WiMAX Receiver- The receiver and
antenna could be a stand-alone box or a PCMCIA card
that sits in your laptop or computer. Access to
WiMAX base station is similar to accessing a Wireless
Access Point in a WiFi network, but the coverage
LTE, or long-term evolution, is a type of mobile
broadband that rivals WiMAX. Both services are IP-based
and use a technology called orthogonal frequency-division
multiplexing (OFDM) access. They also use a type of
wireless technology that lets people get high-speed
Internet across coverage areas that span miles. The
standard is maintained as a project of the 3rd Generation
Partnership Project (3GPP), operating under a name trademarked
by one of the associations within the partnership, the
European Telecommunications Standards Institute (ETSI).
The goal of LTE is to increase the capacity and speed
of wireless data networks utilizing cutting-edge hardware
and DSP techniques that have recently been developed.
Its wireless interface is incompatible with 2G and 3G
networks, and so it must be operated on separate wireless
Features of LTE include an all-IP flat network architecture,
end-to-end QoS including provisions for low-latency
communications, peak download rates nearing 300 mbps
and upload rates of 75 mbps, capacity exceeding 200
active users per cell, the ability to manage fast-moving
mobiles, and support for multi-cast and broadcast streams.
3.5 Describe different network topologies.
A topology is physical and logical network layout. Physical
layout include actual layout of cables and other network
devices where as Logical layout include the way in which
the network appears to the devices that use it.
Mesh : In this topology each computer is connected
to every other. This topology is rarely used.
It has high level of redundancy
wiring is very complicated
Cabling cost is very high
Finding fault in cabling is very tricky
Ring :In this topology each network computer and
device are connected to each other forming a large circle
(or similar shape). Each packet is sent around the ring
until it reaches its final destination. Typically FDDI,
SONET or Token Ring technology are used to implement a ring
BUS : Bus networks use a common backbone to connect
all devices. A single cable, the backbone functions as a
shared communication medium that devices attach or tap into
with an interface connector. A device wanting to communicate
with another device on the network sends a broadcast message
onto the wire that all other devices see, but only the intended
recipient actually accepts and processes the message.
Single fault in cable will disrupt entire
Expansion will cause disruption in current
Troubleshooting is difficult.
Star: In Star topology, all the components of
network are connected to the central device called "hub"
which may be a hub, a router or a switch. All the data on
the star topology passes through the central device before
reaching the intended destination. Hub acts as a junction
to connect different nodes present in Star Network, and
at the same time it manages and controls whole of the network.
Depending on which central device is used, "hub" can act
as repeater or signal booster. Central device can also communicate
with other hubs of different network. Unshielded Twisted
Pair (UTP) Ethernet cable is used to connect workstations
to central node.
Gives better performance compared to BUS
New devices can be added easily.
Centralized management makes monitoring the
network is easier.
Single node failure will not affect entire
If central device (Hub) fails whole network
Use of central device increase overall cost.
Performance of network depends on capacity
of central device.
Hybrid:It is an integration of two or more different
topologies to form a resultant topology. This combination
of topologies is done according to the requirement of the
For example an office can use a star topology in each
of its department and ring topology to connect these departments.
Fault detection is easier.
Size of the network can be increased easily
without distruption to current network.
It is very flexible as network can be designed
according to requirements and available resources.
Overall cost of network is high as it requires
lot of cables, many network devices like HUB
to connect various networks.
Design becomes more and more complex as number
of networks increase