2. Topology Topology refers to the layout of connected devices
on a network. Here, some logical layout of topology. Mesh Star Bus
Ring Tree and Hybrid
3. Network Topology
4. Mesh Topology Here every device has a point to point link to
every other device. Node 1 node must be connected with n-1 nodes. A
fully connected mesh can have n(n-1)/2 physical channels to link n
devices. It must have n-1 I/O ports.
5. Mesh Topology Advantages: 1. They use dedicated links so
each link can only carry its own data load. So traffic problem can
be avoided. 2. It is robust. If any one link get damaged it cannot
affect others. 3. It gives privacy and security.(Message travels
along a dedicated link) 4. Fault identification and fault isolation
are easy.
6. Mesh Topology
7. Mesh Topology
8. Mesh Topology Disadvantages: 1. The amount of cabling and
the number of I/O ports required are very large. Since every device
is connected to each devices through dedicated links. 2. The bulk
of wiring is larger then the available space. 3. Hardware required
to connected each device is highly expensive.
10. Star Topology Here each device has a dedicated
point-to-point link to the central controller called Hub(Act as a
Exchange). There is no direct traffic between devices. The
transmission are occurred only through the central hub. When device
1 wants to send data to device 2; First sends the data to hub.
Which then relays the data to the other connected device.
11. Star Topology
12. Star Topology
13. Star Topology Advantages: 1. Less expensive then mesh since
each device is connected only to the hub. 2. Installation and
configuration are easy. 3. Less cabling is need then mesh. 4.
Robustness.(if one link fails, only that links is affected. All
other links remain active) 5. Easy to fault identification & to
remove parts. 6. No distruptions to the network then connecting(or)
removing devices.
14. Star Topology Disadvantages: 1. Even it requires less
cabling then mesh when compared with other topologies it still
large.(Ring or bus). 2. Dependency(whole n/w dependent on one
single point(hub). When it goes down. The whole system is
dead.
15. Applications Star topology used in Local Area
Networks(LANs). High speed LAN often used STAR.
16. Asynchronous Transfer Mode By the mid 1980s, three types of
communication networks had evolved. The telephone network carries
voice calls, television network carries video transmissions, and
newly emerging computer network carries data. Telephone companies
realized that voice communication was becoming a commodity service
and that the profit margin would decrease over time. They realized
that data communication was increasing. The telecommunication
industry decided to expand its business by developing networks to
carry traffic other than voice.
17. Asynchronous Transfer Mode (ATM) is a switching technique
for telecommunication networks. It uses asynchronous time-division
multiplexing,[1][2] and it encodes data into small, fixed-sized
cells. ATM differs from networks such as the Internet or Ethernet
LANs that use variable sized packets or frames. ATM provides data
link layer services that run over OSI Layer 1 physical links. ATM
has functional similarity with both circuit switched networking and
small packet switched networking. This makes it a good choice for a
network that must handle both traditional high- speed data traffic
(e.g., file transfers), and real-time, low-latency content such as
voice and video. Asynchronous Transfer Mode
18. ATM ATM standard is widely accepted by common carriers as
mode of operation for communication particularly BISDN. ATM is a
form of cell switching using small fixed- sized packets. Header
Payload 5 Bytes 48 Bytes Figure 9.1 Basic ATM Cell Format
Leon-Garcia & Widjaja: Communication NetworksCopyright 2000 The
McGraw Hill Companies
19. ATM is more complex, but this complexity allows to give
guarantees as to data rate, maximum delay, and jitter. These are
usually called Quality of Service. JITTER: In voice over IP (VoIP),
jitter is the variation in the time between packets arriving,
caused by network congestion, timing drift, or route changes. A
jitter buffer can be used to handle jitter. Jitter is the deviation
in or displacement of some aspect of the pulses in a high-
frequency digital signal. Quality of Service or QoS is a method of
providing better service for selected traffic types over various
types of packet-switched networks.
20. Advantages Universality Mixed traffic types, real-time and
non-real-time Scalability LANs, MANs, WANs, WLANs Efficient use of
network resources Bandwidth on demand concept Simplified network
infrastructure
21. Disadvantages ATM has not been widely accepted. Although
some phone companies still use it in their backbone networks. The
expense, complexity and lack of interoperability with other
technologies have prevented ATM from becoming more prevalent.
22. Disadvantages Complexity of QoS: The complexity of the
specification makes implementation cumbersome and difficult. Many
implementations do not support the full standard. Assumption of
Homogeneity: ATM is designed to be a single, universal networking
system. There is minimal provision for interoperating with other
technologies
23. Bus Topology A bus topology is multipoint. Here one long
cable act as a backbone to link all the devices are connected to
the backbone by drop lines and taps. Drop line- is the connection
b/w the devices and the cable. Tap- is the splitter that cut the
main link. This allows only one device to transmit at a time.
24. Bus Topology
25. Bus Topology
26. Bus Topology
27. Bus Topology
28. Bus Topology A device want to communicate with other device
on the n/ws sends a broadcast message onto the wire all other
devices see. But only the intended devices accepts and process the
message.
29. Bus Topology Advantages: 1. Ease of installation 2. Less
cabling Disadvantages: 1. Difficult reconfiguration and fault
isolation. 2. Difficult to add new devices. 3. Signal reflection at
top can degradation in quality. 4. If any fault in backbone can
stops all transmission.
30. Bus Topology Applications: Most computer motherboard.
31. Ring Topology Here each device has a dedicated connection
with two devices on either side. The signal is passed in one
direction from device to device until it reaches the destination
and each device have repeater. When one device received signals
instead of intended another device, its repeater then regenerates
the data and passes them along. To add or delete a device requires
changing only two connections.
32. Ring Topology
33. Ring Topology
34. Ring Topology
35. Ring Topology Advantages: 1. Easy to install. 2. Easy to
reconfigure. 3. Fault identification is easy. Disadvantages: 1.
Unidirectional traffic. 2. Break in a single ring can break entire
network.
36. Ring Topology Applications: Ring topologies are found in
some office buildings or school campuses. Today high speed LANs
made this topology less popular. EX IBM Token Ring,FDDI
37. IBM created IEEE(Institute of Electrical and Electronics
Engineers) 802.5 standard known as Token Ring it uses a special
packet known as Token Multi-station Access Unit (MSAU)
38. A Token Ring network is a local area network (LAN) in which
all computers are connected in a ring or star topology and a bit-
or token-passing scheme is used in order to prevent the collision
of data between two computers that want to send messages at the
same time. The Token Ring protocol is the second most widely-used
protocol on local area networks after Ethernet. The IBM Token Ring
protocol led to a standard version, specified as IEEE 802.5. Both
protocols are used and are very similar. The IEEE 802.5 Token Ring
technology provides for data transfer rates of either 4 or 16
megabits per second.
39. FDDI (Fiber Distributed Data Interface) FDDI is a standard
developed by the American National Standards Institute (ANSI) for
transmitting data on optical fibers Supports transmission rates of
up to 200 Mbps Uses a dual ring First ring used to carry data at
100 Mbps Second ring used for primary backup in case first ring
fails If no backup is needed, second ring can also carry data,
increasing the data rate up to 200 Mbps Supports up to 1000 nodes
Has a range of up to 200 km The possessor of the token is allowed
to put a new token onto the ring as soon as it finished
transmitting its frames
40. Tree Topology Alternatively referred to as a star bus
topology. Tree topology is one of the most common network setups
that is similar to a bus topology and a star topology. A tree
topology connects multiple star networks to other star networks.
Below is a visual example of a simple computer setup on a network
using the star topology.
41. Tree Topology
42. Hybrid Topology A network which contain all type of
physical structure and connected under a single backbone
channel.
43. Hybrid Topology a
44. Considerations for choosing topology Money-Bus n/w may be
the least expensive way to install a n/w. Length-of cable needed-
the linear bus n/w uses shorter lengths of cable. Future
growth-with star topology, expending a n/w is easily done by adding
another devices. Cable type-most common used cable in commercial
organization is twisted pair. Which often used with star
topologies.
45. Full mesh topology is theoretically the best since every
device is connected to every other device.(thus maximizing speed
and security. however, it quite expensive to install) Next best
would be tree topology, which is basically a connection of
star.
46. 1973 by Bob Metacalfe (IEEE standard called 802.3
CSMA/CD)
47. Ethernet Overview Most popular packet-switched LAN
technology Bandwidths: 10Mbps, 100Mbps, 1Gbps Max bus length: 2500m
500m segments with 4 repeaters Bus and Star topologies are used to
connect hosts Hosts attach to network via Ethernet transceiver or
hub or switch Detects line state and sends/receives signals Hubs
are used to facilitate shared connections All hosts on an Ethernet
are competing for access to the medium Switches break this model
Problem: Distributed algorithm that provides fair access
48. Ethernet by definition is a broadcast protocol Any signal
can be received by all hosts Switching enables individual hosts to
communicate Network layer packets are transmitted over an Ethernet
by encapsulating Frame Format Dest addr 64 48 32 CRCPreamble Src
addr Type Body 1648
49. a section of a network where data packets can collide with
one another when being sent on a shared medium the larger the
collision domain, the more likely it is that collision will
occur
50. Carrier Sense Multiple Access/Collision Detect (CSMA/CD) is
the protocol for carrier transmission access in Ethernet networks.
On Ethernet, any device can try to send a frame at any time. Each
device senses whether the line is idle and therefore available to
be used. If it is, the device begins to transmit its first frame.
If another device has tried to send at the same time, a collision
is said to occur and the frames are discarded. Each device then
waits a random amount of time and retries until successful in
getting its transmission sent.
51. Intranet is system in which multiple PCs are connected to
each other. PCs in intranet are not available to the world outside
the intranet. Usually each company or organization has their own
Intranet network and members/employees of that company can access
the computers in their intranet. Each computer in Intranet is also
identified by an IP Address which is unique among the computers in
that Intranet. Intranet (HCL) Intranet (Wipro)Internet
Extranet