1. Networking Types and Topologies

2. Types of Networks WIWIDE AREA NETWORK
Based on the size and the coverage area, networks are categorized into the following types:
Local Area Networks (LANs)
Metropolitan Area Networks (MANs)
Wide Area Networks (WANs)
METRO AREA NETWORK
WIWIDE AREA NETWORK
LOCAL AREA NETWORK

3. LAN Local Area Networks

4. Local Area Networks (LANs)
A local area network (LAN) is a network that connects computers and devices in a limited geographical area such as a home, school, office building, or closely positioned group of buildings.
Each computer or device on the network is a node.
Wired LANs are most likely based on Ethernet technology.
Since it is restricted in size, that means their data transmission time can be known in advance, and the network management would be easier.
A local area network may serve as few as two or three users or as many as thousands of users.
A network which consists of less than 500 interconnected devices across several buildings, is still recognized as a LAN.

5. LAN Cntd…
A local-area network (LAN) is a computer network that spans a
relatively small area(100mtr).
LAN can be connected to other LANs over any distance via telephone
lines and radio waves. A system of LANs connected in this way is
called wide area network(WAN)

6. Types of LANs The three most popular types of LANs are:
Token ring network
FDDI (Fiber Distributed Data Interface) network
Ethernet

7. Token Ring Network Originally developed by IBM in 1970’s
Still IBM’s primary LAN technology
In cases of heavy traffic, the token ring network has higher throughput than Ethernet due to the deterministic (non-random) nature of the medium access
Is used in applications in which delay when sending data must be predictable
Is a robust network i.e. it is fault tolerant through fault management mechanisms
Can support data rates of around 16 Mbps
Typically uses twisted pair

8. 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
Source:

9. Ethernet
First network to provide CSMA/CD is the protocol for carrier transmission access in Ethernet networks.
Developed in 1976 by Xerox PARC (Palo Alto Research Center) in cooperation with DEC and Intel
Standard that has been established in the IEEE-standard
Is a fast and reliable network solution
One of the most widely implemented LAN standards
Can support data rates in the range of 10Mbps- 10 Gbps
Used with a bus or star topology
On Ethernet, any device can try to send a frame at any time.
Carrier Sense Multiple Access/Collision Detect (CSMA/CD) : 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.

10. Local Area Networks

11. Personal Area Network (PAN) as an application of LAN
A personal area network (PAN) is a computer network used for communication among computer and different information technological devices close to one person.
Is a small network established for communication between different devices, such as laptops, computers, mobiles, and PDAs.
A pan may include wired and wireless devices.
The reach of a pan typically extends to 10 meters.

12. Advantages and Disadvantages of LANs
Cost reductions through sharing of information and databases, resources and network services.
Increased information exchange between different departments in an organization, or between individuals.
Improves the communication security (eg. Single department of college).
Increasing number and variety of intelligent data terminals, PCs and workstations. (easy to increase computers specific to single department etc)
Disadvantages:
Special security measures are needed to stop users from using programs and data that they should not have access to;
Networks are difficult to set up and need to be maintained by skilled technicians.
If the file server develops a serious fault, all the users are affected, rather than just one user in the case of a stand-alone machine.

13. MAN Metropolitan Area Networks

14. Metropolitan Area Network (MAN)
‘Metropolitan' - describes important cities like New Delhi, Mumbai, Kolkata, Bangalore, Chennai etc.
Companies that have several branches within the Mumbai city such as banks, use a MAN.
MAN can be defined as a group of computers and network devices connected together within a large physical area.
It is relatively larger than LAN and extends across a city or a metropolitan.
It is created by connecting two or more LANs located at different locations in a city.
MANs have the requirement of using telecommunication media such as voice segments or data segments.
Branch offices are connected to head offices through MANs. Examples of organizations that use MANs are universities and colleges, grocery chains, and banks.

15. Metropolitan Area Networks (MANs)…

16. Advantages and Disadvantages of MAN
It provides a good back bone for a large network and provides greater access to WANs.
The dual bus used in MAN helps the transmission of data in both direction simultaneously.
A Man usually encompasses several blocks of a city or an entire city.
Disadvantages:
More cable required for a MAN connection from one place to another.
It is difficult to make the system secure from hackers and industrial espionage (spying) graphical regions.

17. WAN Wide Area Networks

18. Wide Area Network (WAN)
A wide area network (WAN) is a computer network that covers a large geographic area such as multiple cities, countries or intercontinental distances. Best example: Internet
A WAN uses a communications segment that combines many types of media such as telephone lines, cables, fiber, satellite and air waves.
E.g. Local banks have always maintained their business online by connecting all computers of their branches in the countries. International banks also use WAN to connect their computers all over the world.
WAN is a group of MANs or LANs or the mixture of both networks.
May be privately owned or leased. Also called “enterprise networks” if they are privately owned by a large company.
It can be leased through one or several carriers (ISPs-Internet Service Providers) such as AT&T, Sprint, Cable and Wireless.
Services include internet, frame relay, ATM (Asynchronous Transfer Mode)

19. Wide area network Cntd…
May be privately owned or leased
Also called “enterprise networks” if they are privately owned by a large company
Is typically slower and less reliable than a LAN
Sprint
Network
Sprint provisions a connection between the two networks DC
Runs a 1Gbps LAN

20. Wide Area Networks (WANs)…
WANs connecting LANs between cities
The main difference between a MAN and a WAN is that the WAN uses Long Distance Carriers. Otherwise the same protocols and equipment are used as a MAN.

21. Wide Area Networks (WANs)…

22. Advantages of WAN
Covers a large geographical area so long distance businesses can connect on the one network.
Shares software and resources with connecting workstations.
Messages can be sent very quickly to anyone else on the network. These messages can have pictures, sounds, or data included with them (called attachments).
Expensive things (such as printers or phone lines to the internet) can be shared by all the computers on the network without having to buy a different peripheral for each computer.
Everyone on the network can use the same data. This avoids problems where some users may have older information than others.

23. Disadvantages of WAN
Need a good firewall to restrict outsiders from entering and disrupting the network.
Setting up a network can be an expensive, slow and complicated. The bigger the network the more expensive it is.
Once set up, maintaining a network is a full-time job which requires network supervisors and technicians to be employed.
Security is a real issue when many different people have the ability to use information from other computers. Protection against hackers and viruses adds more complexity and expense.

24. Comparisons of LAN, MAN, WAN

25. Differences between LAN, MAN, WAN
BASIS
LAN
MAN
WAN
Range
A communication network linking a number of stations in same local area. Range is 1 to 10 km
This network shares the characteristics of packet broadcasting networks. Range is100 km
A communication network distinguished from a Local Area Network. Range is Beyond 100 km
Media Used
Uses guided media
Uses guided as well as unguided media
Uses unguided media
Speed
A high speed i.e. 100kbps to 100mbps
Optimized for a large geographical area than LAN.
Long distance communications, which may or may not be provided by public packet network.
Cost
cheaper
costly
expensive
Equipment needed
NIC, switch and hub
Modem and router
Microwave, radio, infra-red laser
Protocols
Attached Resource computer network (ARCNET), Token ring
Frame relay and asynchronous transfer mode(ATM)
ATM, FDDI, SMDS

26. NETWORK ARCHITECTURE
Network architecture is a overall design of a computer network, that describes how a computer network is configured and what strategies are being used. Also known as network model or network design.
Mainly focuses on the functions of the networks.
Types of network models :
Client/Server Network
Peer-to-Peer(P2P)

27. CLIENT/SERVER Architecture
A client/server network is a network in which the shared files and applications are stored in the server but network users (clients) can still store files on their individual PCs.
A server is a computer that shares information and resources with other computers on a network.
A client is a computer which requests services or files from a server computer.

28. Peer-to-peer or P2P Architecture
It is a network with all the nodes acting as both servers and clients.
A PC can access files located on another PC and can also provide files to other PCs.
All computers in the peer-to-peer network has equal responsibilities and capabilities to use the resources available on the network.
With peer-to-peer network, no server is needed; each computer in the network is called a peer.

29. Hybrid Architecture
A hybrid, in general, is a composition of two different types of elements.
A hybrid network architecture is created to get the benefits of both, the peer-to-peer and the client-server architectures, in a network.

30. Differences :

31. NETWORK TOPOLOGIES

32. Network Topologies
Network Topology – Maps of how the physical or logical paths of network devices connect using Hubs/Switches. The pattern of interconnection of nodes in a network is called the Topology.
This layout also determines the manner in which information is exchanged within the network.
The major topologies are:
Ring Topology – Network that is physically wired like a star network but, logically in a ring; passes control from one device to the next in a continuous fashion using a special data packet called a token. Used in Token Ring networks.
Star Topology – Most common Ethernet network topology where each device connects to a central hub or switch.
Bus Topology – Network wherein all devices connect to a single cable. If the cable fails, the network is down.
Mesh Topology – Network where all devices connect to each other by cabling to provide link redundancy for maximum fault tolerance. Most likely in WANs.
Tree Topology – The tree topology is created where the nodes are connected in a hierarchical manner.
Hybrid Topology – The hybrid topology can be a combination of two or more basic topologies
Network devices:
Hub – A device used with the Universal Serial Bus or in a star network topology that allows multiple device connections.
Switch – In star networks, a Layer 2 central controlling device. A switch looks at each data frame as it comes through each port.

33. Diagrammatical Representation

34. Star Topology – WS connected through a Hub/Switch
Network Topologies
Star Topology – WS connected through a Hub/Switch
Network Topologies

35. BUS TOPOLOGY
A bus topology consists of a single central cable to which all computers and other devices connect. A bus topology is also known as a bus network.
DESCRIPTION OF BUS TOPOLOGY
Very common in LAN for data networks.
Must have a common backbone or single transmission medium (the central cable) to connect all devices. Normally coaxial cable is used as transmission medium.
All nodes share the backbone to communicate with each other on the network.
Sometimes, a bus network has more than one server. Sometimes, a server is not needed on the network.
Drawback: Terminators located at both end of BUS absorbs signal, removing it from BUS

36. Ring topology
A ring topology consists of all computers and other devices that are connected in a loop through a point-to-point connection. Ring topology is also known as a ring network.
DESCRIPTION OF RING TOPOLOGY
Can be found in LAN.
Each node directly connect to two neighboring nodes. Data is accepted from one neighboring node and transmitted to other. Data travels in one direction.
A server may exist in a ring network, but it will not connect to all the nodes in the network. Hence server, like other nodes, will only communicate to its two neighboring nodes
Drawback: If one node on the network stops, the entire network stops functioning.

37. Star topology
A star topology consists of a central host which acts as the centre, and all nodes connect to the host. A star topology is also known as star network.
DESCRIPTION OF STAR TOPOLOGY
A star network is found in a LAN setting.
A star network must have a host which acts as the centre.
The host can be a server, hub or router.
In a star network, every node will not connect to the neighboring nodes instead every node must connect to the host in order to communicate.
Hence new nodes can be easily added to these networks by attaching the required nodes to the hub or router.

38. Star topology DESCRIPTION OF STAR TOPOLOGY Drawbacks :
The host will control the flow of communication in the network. Hence if host id down then communication stops.
Setting up a star topology requires a lot of cabling because all the nodes have to connect to the hub.

39. Mesh topology
Mesh Network is a network where all the nodes are connected to each other and is a complete network. In a Mesh Network every node is connected to other nodes on the network through hops. It is called the self healing technology where it receives data one way or the other.
DESCRIPTION OF MESH TOPOLOGY
Used in large internetworking environments with stars, rings, buses as nodes.
Each node is connected to more than one node. This provide an alternate route mechanism supporting back-up and rerouting.
Data is automatically configured to reach the destination by taking the shortest route. (used by routing protocols like OSPF). Hence excellent for long distances.
The reliability factor is high in any kind of Mesh Network.
The Mesh Network is based on a very sensible concept
and has lesser chances of a network breakdown.

40. DESCRIPTION OF TREE TOPOLOGY
Tree topology is the combination of the bus and the star topology. The tree like structure allows you to have many servers on the network and you can branch out the network on many ways. Also known as hierarchical network.
DESCRIPTION OF TREE TOPOLOGY
The tree topology is created where the nodes are connected in a hierarchical manner.
In tree topology, the device at the root is referred to as the parent for all the other nodes or devices in the network.
The nodes below a parent node are referred to as child nodes.
Nodes of some devices are linked to a centrally located hub which is called the active hub.

41. DESCRIPTION OF TREE TOPOLOGY
The active hub has a hardware device called the repeater.
This Strengthens the transmission and increases the travelling distance of a signal.
The secondary hub can isolate communications between different computers.

42. Hybrid Topology
The hybrid topology can be a combination of two or more basic topologies, such as bus, ring, star, mesh, or tree.
Hybrid networks combine more than two topologies, which, in turn, enable  you to get advantages of the constituent topologies.

43. Network Topologies
Network Topologies
Network – Table # 1

44. Differences : Bus Topology Ring Topology Star Topology Structure
there is a single
central cable (backbone) and all computers and other devices connect to it
all computers and other devices are
connected in a circle
there is a central host and all nodes
connect to it
Host existence
depends on network
needs
depends on network needs
yes
Connection
between nodes
It has no connection between the nodes. no
Host failure
network can still run
network will fail
Node failure
Ease of
troubleshooting
difficult. Need to
search for the
problematic node one by one
depends on backbone. If there is a backbone,
troubleshooting is
difficult. If there is no backbone, the focus is on the two nodes not communicating
depends on the host. It
is easier to repair the problematic host. However, if the nodes fail, then each node has to be searched
Ease of adding
or removing nodes
easy
difficult
average
Number of nodes when extending network
many
limited

45. Overview of LAN Technology - Ethernet

46. What is Ethernet ?
Developed in 1976 by Xerox PARC (Palo Alto Research Center) in cooperation with DEC and Intel
Standard that has been established in the IEEE-standard
First network to provide CSMA/CD is the protocol for carrier transmission access in Ethernet networks.
Carrier Sense Multiple Access/Collision Detect (CSMA/CD) : 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.
Is a fast and reliable network solution
Ethernet is one of the most widely implemented LAN standards
Can support data rates/bandwidth in the range of 10Mbps- 10 Gbps
Used with different topologies
On Ethernet, any device can try to send a frame at any time.
Ethernet is a certain type of a local area network (LAN)
Cabling and signaling schemes were invented at Xerox

47. Ethernet Evolution Through Four Generatipon

48. Ethernet topologies
Bus
Star
Ring

49. Coaxial cable Ethernet cable types
Twisted pair as the name indicates is a pair of cable that are twisted around each other. The basic advantage is that any external electromagentic and electrostatic noise gets cancelled out due to the twists.
The number of twists/length or the spacing between the twists has a direct bearing on the performance of that the cable can support. Cross talk is reduced by having different twists/length for adjacent pairs of cables.
The thickness of the conductor determines what is the resistive attenuation and hence what is the distance between two repeaters. The basic function of a repeater is to clean up and amplify the signal to its original levels and then retransmit. The thickness is measured in gauge or mm diameter. Typically a 24AWG thickness is equal to 0.50 mm diameter.
A shield around each pair of twisted cable protects the data from cross talk – data in adjacent pairs affecting each other and also external noise. There are two different shield – a foil surrounding each twisted pair
A coaxial cable has the pair of conductors – one inside the other cylindrically. They are separated by an insulator ring.
An optical fibre cable would consist of a glass core – the conducting fibre surrounded by a cladding. Additionally there is a protective plastic sheath and a strengthening cover. The digital bits are converted in to optical signals that get transmitted through the glass fibre through total internal reflection.
The transmission characteristics in fibre is determined by the way the light reflects inside the glass. There are different types of glasses classified based on the impurity levels – step-index multimode fibre, graded-index multimode fibre and single mode fibre

50. Connectors for UTP/STP, coaxial and optical fibre cables
Here are a few common connectors used for connecting and terminating UTP/FTP, coaxial cables. These are used for point to point connections.

51. Ethernet Media
A big part of designing and installing an Ethernet system is using the right medium. A large selection of cables is a result of Ethernet evolution over the years and Ethernet flexibility.
The three major types of media in use today are:
• Coax
- Thick wire 10Base-5
- Thin wire 10Base-2
• Twisted pair
- 10Base-T
- 100Base-T (twisted pair and fiber-optic cable)
- 1000Base-T
• Fiber optic
- 10Base-F
- 1000Base-X
The first Ethernet systems used 10Base-5 coax cable. The name identifies different functions and limitations of the cabling:
• Mb/s bandwidth of the signal
• Base - Cable carries only Ethernet
• meters is the longest distance a cable segment can carry the signal
The expensive thick wire cable (10 mm) was soon replaced by less expensive, but less efficient, 10Base-2 thin wire cable. The maximum range for thin wire is 185 meters (that rounded up to 2
for the name of the cable).

52. Ethernet Media Cntd...
The most popular Ethernet wiring is UTP (unshielded twisted pair) cable that comes in a wide variety of grades (categories), performance levels.
The UTP cable is similar to telephone plug cable, straight through or crossover. Straight through connections are used in most Ethernet networks.
Crossover cables can connect two computers directly to each other without the use of a hub.
Cat. 3 to Cat. 5 UTP is used for 10Base-T and 100Base-T electrical signals. Cat. 5 or better is used for 1000Base-T.
Fiber optic cables are gaining more in popularity, more expensive than electrical cable, unaffected by many environmental conditions that can be problems for coax or UTP.
SMF optic cable provides practically unlimited bandwidth expandability and the ability to transmit Ethernet signals considerably longer distances.
The most commonly used cable today is 10Base-FL (L stands for link), The 1993 standard updated the older DIX standard for Fiber Optic.
The newest and largest Ethernet networking configuration is 1000Base-X or Gigabit Ethernet, along with 10 Gig Ethernet. Short wavelength (1000Base-SX) and long wavelength (1000Base-LX) are based on an 8B/10B block encoding scheme.

53. Ethernet Media Cntd ... Example: 10base5 10 Transmission rate in Mbps
Cabling
Connector
10Base-2
Thin Ethernet
Thinwire (RG-58) coax
BNC
10Base-5
Thick Ethernet
Thickwire (10mm) coax
RG-8
10Base-T1
Unshielded twisted pair (UTP)
UTP Category 3 (Cat. 3)
RJ-45
100Base-T
UTP and fiber optics
UTP Cat. 3 to Cat. 5
RJ-45 and FC, ST, SC, LC
1000Base-T
UTP
UTP Cat. 5 and greater
10Base-FX2
Fiber optic
Single-mode fiber (SMF) or multimode
fiber (MMF)
FC, ST, SC, LC
1000Base-SX
1000Base-LX
Short wavelength
Long wavelength
Example: 10base5
10 Transmission rate in Mbps
base Base or Broadband
5 Segment length 500 meters
UTP unshielded twisted pair
STP shielded twisted pair
S/STP screened shielded twisted pair

54. Categories of 10 Mbps Traditional Ethernet
<Bandwidth/data rate><Signaling method><Max segment length or cable type>

55. 10Base-5 and 10Base-2 Implementation

56. 10Base-T & 10Base-F Implementation

57. Fast Ethernet 100 Mbps transmission rate i.e. Bandwidth
same frame format, media access, and collision detection rules as 10 Mbps Ethernet
can combine 10 Mbps Ethernet and Fast Ethernet on same network using a switch
media: twisted pair (CAT 5) or fiber optic cable (no coax)
Star-wire topology - similar to 10BASE-T
CAT 3
CAT 5

58. Fast Ethernet

59. Gigabit Ethernet Bandwidth/Speed 1Gpbs
Minimum frame length is 512 bytes
Operates in full/half duplex modes mostly full duplex

60. Gigabit Ethernet Implementations

61. 10 Gbps Ethernet Bandwidth/Speed 10 Gpbs
Maximum link distances cover 300 m to 40 km
Full-duplex mode only
No CSMA/CD
Uses optical fiber only

62. Topologies of Gigabit Ethernet

63. Access Method and Speed/Bandwidth
IEEE 802.3
Bandwidth: 10 Mbps
IEEE 802.3u
Bandwidth: 100 Mbps
Also known as fast Ethernet
IEEE 802.3z
Bandwidth: 1 Gbps
Also known as gigabit Ethernet
IEEE 802.3ae
Bandwidth: 10 Gbps
Also known as 10-gigabit Ethernet

64. Types of Addresses in Internet
Media Access Control (MAC) addresses in the network access layer
Associated w/ network interface card (NIC)
48 bits
IP addresses for the network layer
32 bits for IPv4, and 128 bits for IPv6
E.g.,
IP addresses + ports for the transport layer
E.g., :80
Domain names for the application/human layer
E.g.,
CS426
Fall 2010/Lecture 33

65. Networking Devices

66. Why internetworking devices?
Internetworking devices are products used to connect networks. As computer networks grow in size and complexity, so do the internetworking devices used to connect them.
Networks cannot be made larger (expanding) by simply adding new computers and more cables
Devices are used for Separating (connecting) networks or expanding network
Some devices are required to
segment (divide) large LAN to form smaller LANs
connect LANs
Devices allow a greater number of nodes to be connected to the network.
Second, they extend the distance over which a network can extend.
Third, they localize traffic on the network.
Fourth, they can merge existing networks.
Fifth, they isolate network problems so that they can be diagnosed more easily.

67. Why internetworking devices? Cntd …
To connect two LANs with different protocols.
To connect a LAN to the Internet.
To break a LAN into segments to relieve traffic congestion.
To provide a security wall between two different types of users.
To connect WLAN to LAN

68. Internetworking Devices
The key Network Devices with their increasing power and complexity
Repeaters
Hubs
Bridges
Switches
Routers
Many times it is necessary to connect a LAN to another LAN or to a WAN.
Computers on different segments of a network (within a LAN) are often connected using a Hub
Different segments on different networks (LAN to LAN connections) are often performed with a Bridge.
Segments of a LAN are usually connected using a Switch.
LAN to WAN connections are usually performed with a Router.

69. Devices and the OSI Layers at which they operate
Name of Layer
Device
Layer-1
Physical
Repeater
Hub
Layer-2
Data Link
Switches
Bridges
Layer-3
Network
Routers

70. OSI Layer-1 Device - Repeaters
Used for extending the physical span of a network - Used when you need to go farther distances than the cabling will allow
Usually has 2 ports (IN/OUT)
Span is often limited by design considerations
10base5 - The span is limited to 500 meters
A Repeater is used when signals first leave a transmitting station, they are clean and easily recognizable. However, the longer the cable length, the weaker and more deteriorated the signals become as they pass along the networking media.
Repeaters connect all other LAN segments of a network

71. Fig - Extending the distance between the backbone and the nodes.
A Repeater Connection
Fig - Extending the distance between the backbone and the nodes.
Fig- Expanding the Span of the Network
Source: Black Box

72. Operations of a Repeater Within the ISO OSI Model
Operates at the lower level of the ISO OSI model
Physical layer
Physical
Layer
Repeater
Physical
Layer
Medium
Medium

73. OSI Layer-1 Device: Hub A device that contains multiple ports
Has no logic or “brain”, simply passes data out all other ports
Multi-port repeaters are often called hubs. Hubs are very common internetworking devices.
A hub interconnects two or more workstations into a local area network.
When a workstation transmits to a hub, the hub immediately resends the data frame to all connecting links.
Hubs expand one Ethernet connection into many. For example, a four-port hub connects up to four machines
The most economic way of expanding networks .

74. Hubs – Limitations Hubs cannot link unlike segments
Hubs cannot join segments with different access methods (e.g. CSMA/CD and token passing)
Hubs cannot isolate and filter packets/network traffic
They work in crossover mode or straight through mode

75. Disadvantage with using a Repeaters and Hubs
Repeater/Hub can't filter network traffic. Data, referred to as bits, arriving at one port of a repeater gets sent out on all other ports
Data gets passed along by a repeater to all other LAN segments of a network regardless of whether it needs to go there or not.
Too much traffic on a network?
If segments of a network are only connected by non-filtering devices such as repeaters, this can result in more than one user trying to send data on the network at the same time
If more than one node attempts to transmit at the same time, a collision will occur.
When a collision occurs, the data from each device impact and are damaged

76. Bridge: OSI Layer-2 Device
Bridge is a device used for connecting two LANs operating under the same protocol
Currently, the term bridge is loosely being used to describe different interconnecting devices
Used now for connecting LANs operating under different protocols as well
Facilitate the movement of data packet from one network segment to another
Connects two network segments and not multiple network segments
A Bridge has one input and one output
Bridge is used to isolate network traffic and computers
Has the intelligent to examine incoming packet source and destination addresses
Filter traffic by looking at the MAC address and does Frame filtering

77. Practical Bridge Examples

78. Bridge: OSI Layer-2 Device – How it works
Bridges maintain a MAC address table for both segments they are connected to.
Bridged network can span many segments Bridges work at the MAC Sub-layer of the Data Link Layer
Broadcasts are sent to all segments
If the frame is destined to a MAC address on the local side of the bridge, it is not forwarded to the other segment
MAC addresses on the other segment are forwarded - collects and pass packets between two network segments

79. Bridge: OSI Layer-2 Device – How Data is Forwarded

80. Selective Forwarding A B E F BRIDGE C D G H
If A sends a frame to E - the frame must be forwarded by the bridge.
If A sends a frame to B - there is no reason to forward the frame.

81. Bridge Database
The bridge needs a database that contains information about which hosts are on which network.
The realistic options are:
The system administrator can create and maintain the database.
The bridge can acquire the database on the fly.
Hard to add
new computers
Some loss of efficiency

82. Switch: OSI Layer-2 Device
A switch is defined as a device that allows a LAN to be segmented
The segments will operate under the same protocol
A switch focuses on segmenting a LAN i.e. Switches divide a network into several isolated segments
Switches operate at the Data Link layer (layer 2) of the OSI model
Can interpret address information
A bridge is concerned with linking two network segments that operate under different protocols
Switches resemble bridges and can be considered as multiport bridges
By having multiports, can better use limited bandwidth and prove more cost- effective than bridge

83. Performance Improvement & Reliability in Segmented Networks
Performance is improved especially in the case of a bus network
Multiple bus paths are now available for communication
Each segment can engage in simultaneous communication within itself
Easier to isolate a problem to a segment
Thus, better manage the entire network
When one segment does not function, the other segments can continue to function
Offers better reliability to at least part of the function

84. Hub Switch Switch: OSI Layer-2 How they work 3.3Mbps 10Mbps 3.3Mbps
Switches divide a network into several isolated segments
Packets sending from 1 segment will not go to another if not specify
Each segment has its own capacity and need not be shared with other segments
Hub
3.3Mbps
10Mbps
3.3Mbps
Switch
3.3Mbps
10Mbps
10Mbps
10Mbps

85. Switch: OSI Layer-2 Device - Advantages
Switches divide a network into several isolated segments (or collision domains)
Reduce the possibility of collision
Collision only occurs when two devices try to get access to one segment
Can be solved by buffering one of them for later access
Each segment has its own network capacity
Suitable for real-time applications, e.g. video conferencing
Since isolated, hence secure
Data will only go to the destination, but not others

86. Switch: OSI Layer-2 Device - Limitations
Although contains buffers to accommodate bursts of traffic, can become overwhelmed by heavy traffic
Device cannot detect collision when buffer full
CSMA/CD scheme will not work since the data segments are isolated, not the case as in Ethernet
Some higher level protocols do not detect error
E.g. UDP
Those data packets are continuously pumped to the switch and introduce more problems

87. Types of Switching Technologies
There are two major types of switching technologies
Cut-through
Store-and-forward
Header Sender’s Add Receivers Add
Data
Cut-through
Store-and-forward

88. 7 Bytes 1 Byte 2/6 Bytes 2/6 Bytes 2 Bytes 4 Bytes
Switch: OSI Layer-2 Device – Cut Through Mode
Preamble
Des. Add
Sour. Add
Length
Data
FCS 7
Bytes 1
Byte
2/6
Bytes
2/6
Bytes 2
Bytes
Bytes 4
Bytes
Read the first 14 bytes of each packet, then transmit
Much faster
Cannot detect corrupt packets
Can propagate the corrupt packets to the network
Best suited to small workgroups

89. 100Mbps 10Mbps Switch: OSI Layer-2 Store & Forward Mode
Read the whole packet before transmit
Slower than the cut-through mode
More accurate since corrupt packets can be detected using the FCS
More suit to large LAN since they will not propagate error packets
Facilitate data transfer between segments of different speed DB
100Mbps
10Mbps

90. Switch: OSI Layer-2 Using Switches to Create VLANs
Switches can logically group together some ports to form a virtual local area network (VLAN)
SW1
VLAN1
VLAN2
Hub
SW2
Hub
Switches can be configured to communicate only within the devices in the group
SW3
Hub

91. Use of Switches in Linking LAN Segments
Crossover Traffic
Switch
Segment 2
Segment 1
Hub
Hub WS
Server WS
Server

92. Using A Switch to Link Bus LAN Segments

93. Use of Switches for Higher Bandwidth
100 MBps Switch WS WS WS WS
Each port in theory has a bandwidth of 100 Mbps.

94. Routers: OSI Layer-3 Device
Routers are another type of internetworking device, which operates at OSI Layer-3 i.e. Network Layer
These devices pass data packets between networks based on routing protocol or layer 3 information.
Routers have the ability to make intelligent decisions as to the best path for delivery of data on the network.
Layer 2 Switches cannot take advantage of multiple paths

95. Routers: OSI Layer-3 Device: How they Work
They use the destination “IP Address” of packets and routing tables to determine the best path for data delivery
As packets are passed from routers to routers, Data Link layer source and destination addresses are stripped off and then recreated
Enables a router to route a packet from a TCP/IP Ethernet network to a TCP/IP token ring network or any network
Only packets with known network addresses will be passed - hence reduce traffic
Routers can listen to a network and identify its busiest path
Will select the most cost effective path for transmitting packets

96. Router Components Hardware components of a router: Network interfaces
Interconnection network
Processor with a memory and CPU
PC router:
interconnection network is the (PCI) bus and interface cards are NICs
All forwarding and routing is done on central processor
Commercial routers:
Interconnection network and interface cards are sophisticated
Processor is only responsible for control functions (route processor)
Almost all forwarding is done on interface cards

97. Functional Components
Control
Datapath:
per-packet
processing

98. Routing and Forwarding
Routing functions include:
route calculation
maintenance of the routing table
execution of routing protocols
On commercial routers handled by a single general purpose processor, called route processor
IP forwarding is per-packet processing
On high-end commercial routers, IP forwarding is distributed
Most work is done on the interface cards

99. Basic Architectural Components Per-packet processing
Output
Scheduling
Routing
Table
Switch Fabric
Routing
Decision
Routing
Table
Forwarding
Decision
Routing
Table
Forwarding
Decision

100. Router Components On a PC router:
interconnection network is the (PCI) bus
Interface cards are NICs (e.g., Ethernet cards)
All forwarding and routing is done on central processor
On Commercial routers:
Interconnection network and interface cards can be sophisticated
Central processor is the route processor (only responsible for control functions)

101. Slotted Chassis Large routers are built as a slotted chassis
Interface cards are inserted in the slots
Route processor is also inserted as a slot
This simplifies repairs and upgrades of components

102. Evolution of Router Architectures
Early routers were essentially general purpose computers
Today, high-performance routers resemble supercomputers
Exploit parallelism
Special hardware components
Until 1980s (1st generation): standard computer
Early 1990s (2nd generation): delegate to interfaces
Late 1990s (3rd generation): Distributed architecture
Today: Distributed over multiple racks

103. 1st Generation Routers
This architecture is still used in low end routers
Arriving packets are copied to main memory via direct memory access (DMA)
Interconnection network is a backplane (shared bus)
All IP forwarding functions are performed in the central processor.
Routing cache at processor can accelerate the routing table lookup.
Drawbacks:
Forwarding Performance is limited by CPU
Capacity of shared bus limits the number of interface cards that can be connected

104. 2nd Generation Routers Keeps shared bus architecture,
but offloads most IP forwarding to interface cards
Interface cards have local route cache and processing elements
Fast path: If routing entry is found in local cache, forward packet directly to outgoing interface
Slow path: If routing table entry is not in cache, packet must be handled by central CPU
Drawbacks: Shared bus is still bottleneck

105. Another 2nd Generation Architecture
IP forwarding is done by separate components (Forwarding Engines)
Forwarding operations:
Packet received on interface: Store the packet in local memory. Extracts IP header and sent to one forwarding engine
Forwarding engine does lookup, updates IP header, and sends it back to incoming interface
Packet is reconstructed and sent to outgoing interface.

106. 3rd Generation Architecture
Interconnection network is a switch fabric (e.g., a crossbar switch)
Distributed architecture:
Interface cards operate independent of each other
No centralized processing for IP forwarding
These routers can be scaled to many hundred interface cards and to aggregate capacity of > 1 Terabit per second

107. Aggregation Router Reinventing Edge Routing
The Cisco ASR 1000 Series Aggregation Services Routers transform the service provider and enterprise network edge by delivering industry-leading performance, instant-on service capabilities, and high availability in a compact form factor.
The Cisco ASR 1000 Series Routers deliver:
Highly secure, high-performance, and integrated software-enabled services
A new price class for high-performance edge routers
High resiliency with convenient and cost-saving, in-service software upgrades
Software redundancy on non-redundant hardware
For service providers, the Cisco ASR 1000 Series facilitates more flexible, efficient, and cost-effective delivery of complex consumer and business services. And for enterprises, it delivers a highly reliable, high-performance WAN edge solution where information, communication, collaboration, and commerce converge.

108. Thank You