2012

Siemens Industrial

Training Report Industrial Training Report

Srinidhi Bheesette

Siemens Industrial Training Report 2012

Srinidhi Bheesette Page 1

Mentor- Mr. Prashant Gavade

Topic-Data Networking

Networking is required to allow multiple computers to connect to each other and share data. There

are some basic components which are used for establishing a network, there are switch, router and

clients (the laptops or computers).

To connect these computers there are two types of cable:

Straight cable: This is used for connecting non-identical elements.

1. Switch to router

2. Switch to PC or server.

Crossover cable: This is used for connecting identical elements.

1. Switch to switch

2. PC to PC

3. Hub to hub

4. Router to router

5. Switch to hub

Every client (PC or laptop) is identified using a unique name, here known as IP (Internet Protocol)

address. It is a 32 bit address divided into 4 octaves each, e.g. : 192.168.10.1,168.187.12.42 etc.

There are 5 types of IP addresses:

Class A-N.H.H.H

Class B-N.N.H.H

Class C-N.N.N.H

Class D-multicasting

Class E-Research and Development

The table.1 gives the information about the various IP address (its decimal range, octal bits,

network/host ID, subnet mask, number of networks and the no of host per network)

Figure 1: Straight and Cross cable connections

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Table.1 Different Category (CAT) cables

Each device also consists of a Network Identification Card (NIC) which is used to connect to a

network through a switch. Every NIC consists of a unique MAC (Media Access Control) number,

e.g.:9C-8E-99-43-56-A7, here the first 4bits (i.e.9C-8E) specify the name of the manufacturer(here

Realtek).

Every data communication over the network takes place over two protocols: TCP/IP and UDP.

TCP/IP stands for Transfer Control Protocol/Internet Protocol. In this type the every time the source

send data it expects an acknowledgement, thus it has control over the data and it decides whether

to transmit more data or not But this feature is not present in UDP (User Datagram Protocol),thus

this protocol does not have control over the data, it sends data even if the receiver does not respond

to it.

Comparing TCP/IP and UDP:

TCP/IP UDP

Sequence Non-sequence

Reliable Non-Reliable

Connection oriented Not connection oriented

Virtual circuit Low overhead

Acknowledge No acknowledgment

Window flowing is present No windowing

DHCP:

DHCP stands for Dynamic Host Control Protocol. It is a device which is connected to the switch in the

network topology which is used to automatically assign a unique IP address to each client connected

in the network. This is used when it is not possible to configure many multiple computers connected

to the network.

The Dynamic Host Configuration Protocol (DHCP) is a network configuration protocol for hosts

on Internet Protocol (IP) networks. Computers that are connected to IP networks must be

configured before they can communicate with other hosts. The most essential information needed is

an IP address, and a default route and routing prefix. DHCP eliminates the manual task by a network

administrator. It also provides a central database of devices that are connected to the network and

eliminates duplicate resource assignments.

In addition to IP addresses, DHCP also provides other configuration information, particularly the IP

addresses of local Domain Name Server (DNS), network boot servers, or other service hosts.

Table.2 TCP/IP vs. UDP

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DHCP is used for IPv4 as well as IPv6. While both versions serve much the same purpose, the details

of the protocol for IPv4 and IPv6 are sufficiently different that they may be considered separate

protocols.[1]

Hosts that do not use DHCP for address configuration may still use it to obtain other configuration

information. Alternatively, IPv6 hosts may use stateless address auto configuration. IPv4 hosts may

use link-local addressing to achieve limited local connectivity.

For example:

192.168.10.1..10.2......192.168.10.10 are some set of IPs to be allocated to 10 clients.

Figure 2 : DHCP status in network details

Figure 3: DHCP settings

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Types of networks:

LAN-Local Area Network

MAN- Metropolitan Area Network

WAN-Wide Area Network

Local Area Network (LAN):

Local area network is network connecting computers or laptop in a confined area radius of about

100-400m. It is within a community, college, hotel, office etc. A local area network (LAN) is

a computer network that interconnects computers in a limited area such as a home, school,

computer laboratory, or office building using network media.[1]The defining characteristics of LANs,

in contrast to wide area networks (WANs), include their usually higher data-transfer rates, smaller

geographic area, and lack of a need for leased telecommunication lines.

ARCNET, Token Ring and other technology standards have been used in the past,

but Ethernet over twisted pair cabling, and Wi-Fi are the two most common technologies currently

used to build LANs.

Metropolitan Area Network (MAN):

A MAN is optimized for a larger geographical area than a LAN, ranging from several blocks of

buildings to entire cities. MANs can also depend on communications channels of moderate-to-high

data rates. A MAN might be owned and operated by a single organization, but it usually will be used

by many individuals and organizations. MANs might also be owned and operated as public utilities.

They will often provide means for internetworking of local networks.

Wide Area Network (WAN):

As the name suggests this network is spread over several kilometres and is used to communicate

with other countries. In this type of network the data to be communicated is transmitted over a

satellite which broadcasts it in the given direction.

A Wide Area Network (WAN) is a telecommunication network that covers a broad area (i.e., any

network that links across metropolitan, regional, or national boundaries). Business and government

entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various

geographical locations. In essence this mode of telecommunication allows a business to effectively

carry out its daily function regardless of location.

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Topologies:

Topology is the pattern in which different computers are connected in the network. The type of

topology should be chosen in such a manner that each computer of the network should be able to

communicate with any other computer.

Types of topologies:

Bus: A linear bus topology consists of a main run of cable with a terminator at each end (See

fig. 4). All nodes (file server, workstations, and peripherals) are connected to the linear

cable.

Star: A star topology is designed with each node (file server, workstations, and peripherals)

connected directly to a central network hub, switch, or concentrator. Data on a star network

passes through the hub, switch, or concentrator before continuing to its destination. The hub,

switch, or concentrator manages and controls all functions of the network. It also acts as a

repeater for the data flow. This configuration is common with twisted pair cable; however, it can

also be used with coaxial cable or fibre optic cable.

Figure 3: LAN and WAN layout

Figure 4: Bus topology

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Ring: In Ring Topology, all the nodes are connected to each-other in such a way that they

make a closed loop. Each workstation is connected to two other components on either side,

and it communicates with these two adjacent neighbours. Data travels around the network,

in one direction. Sending and receiving of data takes place by the help of TOKEN. (See fig6)

Extended Star: A type of network topology in which a network that is based upon the

physical star topology has one or more repeaters between the central node (the 'hub' of the

star) and the peripheral or 'spoke' nodes, the repeaters being used to extend the maximum

transmission distance of the point-to-point links between the central node and the

peripheral nodes beyond that which is supported by the transmitter power of the central

node or beyond that which is supported by the standard upon which the physical layer of

the physical star network is based.

If the repeaters in a network that is based upon the physical extended star topology are

replaced with hubs or switches, then a hybrid network topology is created that is referred to

as a physical hierarchical star topology, although some texts make no distinction between

the two topologies.

Figure 5: Star Topology

Figure 6: Ring Topology

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Figure 7: Extended star topology

Mesh: A network setup where each computer and network device is interconnected with

one another, allowing for most transmissions to be distributed, even if one of the

connections go down. This topology is not commonly used for most computer networks as it

is difficult and expensive to have redundant connection to every computer. However, this

topology is commonly used for wireless networks. Below is a visual example of a simple

computer setup on a network using a mesh topology. See figure 8.

IEEE standard:

IEEE 802 refers to a family of IEEE standards dealing with local area networks and metropolitan area

networks. More specifically, the IEEE 802 standards are restricted to networks carrying variable-size

packets. (By contrast, in cell relay networks data is transmitted in short, uniformly sized units called

cells. Isochronous networks, where data is transmitted as a steady stream of octets, or groups of

octets, at regular time intervals, are also out of the scope of this standard.) The number 802 was

simply the next free number IEEE could assign, though “802” is sometimes associated with the date

the first meeting was held — February 1980.

Figure 8: Mesh Topology

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IEEE standard Application

802.1 Bridging (networking) and Network

Management

802.2 OSI

802.3 MAC/Ethernet

802.6 MANs (DQDB) Table 3: IEE Standard with their applications

CSMA/CD: It stands for Carrier Sense Multiple Access/Collation Detection.

Carrier sense multiple access with collision detection (CSMA/CD) is a Media Access Control method

in which:

a carrier sensing scheme is used.

a transmitting data station that detects another signal while transmitting a frame, stops

transmitting that frame, transmits a jam signal, and then waits for a random time interval before

trying to resend the frame.

CSMA/CD is a modification of pure carrier sense multiple access (CSMA). CSMA/CD is used to

improve CSMA performance by terminating transmission as soon as a collision is detected, thus

shortening the time required before a retry can be attempted. The algorithm is show below. (See

figure 9).

Figure 9: The flowchart of CSMA/CA

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OSI model:

The Open Systems Interconnection (OSI) model is a product of the Open Systems

Interconnection effort at the International Organization for Standardization. It is a prescription of

characterising and standardising the functions of a communications system in terms of abstraction

layers. Similar communication functions are grouped into logical layers. A layer serves the layer

above it and is served by the layer below it.

For example, a layer that provides error-free communications across a network provides the path

needed by applications above it, while it calls the next lower layer to send and receive packets that

make up the contents of that path. Two instances at one layer are connected by a horizontal

connection on that layer.

Layer 7-Application layer: It deals with the network applications like E-Mail, Web Browser etc. This

layer interacts with software applications that implement a communicating component. Such

application programs fall outside the scope of the OSI model. Application-layer functions typically

include identifying communication partners, determining resource availability, and synchronizing

communication. When identifying communication partners, the application layer determines the

identity and availability of communication partners for an application with data to transmit.

Layer 6-Presentation Layer:

The presentation layer establishes context between application-layer entities, in which the higher-

layer entities may use different syntax and semantics if the presentation service provides a mapping

between them. If a mapping is available, presentation service data units are encapsulated into

session protocol data units, and passed down the stack.

Layer 5-Session Layer:

It talks about the sessions like Simplex, Half duplex or Full duplex.The session layer controls the

dialogues (connections) between computers. It establishes, manages and terminates the

Figure 10: OSI model

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connections between the local and remote application. It provides for full-duplex, half-duplex,

or simplex operation, and establishes check pointing, adjournment, termination, and restart

procedures. The OSI model made this layer responsible for graceful close of sessions, which is a

property of the Transmission Control Protocol, and also for session check pointing and recovery,

which is not usually used in the Internet Protocol Suite.

Layer 4-Transport Layer:

The transport layer provides transparent transfer of data between end users, providing reliable data

transfer services to the upper layers. The transport layer controls the reliability of a given link

through flow control, segmentation/desegmentation, and error control. Some protocols are state-

and connection-oriented. This means that the transport layer can keep track of the segments and

retransmit those that fail. The transport layer also provides the acknowledgement of the successful

data transmission and sends the next data if no errors occurred.

Layer 3-Network Layer:

The network layer provides the functional and procedural means of transferring variable

length data sequences from a source host on one network to a destination host on a different

network (in contrast to the data link layer which connects hosts within the same network), while

maintaining the quality of service requested by the transport layer. The network layer performs

network routing functions, and might also perform fragmentation and reassembly, and report

delivery errors. Routers operate at this layer, sending data throughout the extended network and

making the Internet possible.

Layer 2-Data Link:

The data link layer provides the functional and procedural means to transfer data between network

entities and to detect and possibly correct errors that may occur in the physical layer. Originally, this

layer was intended for point-to-point and point-to-multipoint media, characteristic of wide area

media in the telephone system. Local area network architecture, which included broadcast-capable

multi-access media, was developed independently of the ISO work in IEEE Project 802. IEEE work

assumed sub layering and management functions not required for WAN use

Layer 1: Physical Layer:

The major functions and services performed by the physical layer are:

Establishment and termination of a connection to a communications medium.

Participation in the process whereby the communication resources are effectively shared among

multiple users. For example, contention resolution and flow control.

Modulation or conversion between the representation of digital data in user equipment and the

corresponding signals transmitted over a communications channel. These are signals operating

over the physical cabling (such as copper and optical fibre) or over a radio link.

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The layers and their functions in a tabular form are shown below:

TCP/IP Layer: The TCP/IP is similar to the OSI model except the fact that the presentation and

Session layer is absent in TCP/IP model, hence it consists of only 4 layers

Table 4: OSI layers and functions in tabular form

Figure 11: OSI and the TCP/IP model

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Category cables:

In the context of the 100-ohm UTP (Unshielded Twisted Pair) type of cable used for Ethernet wiring the only categories of interest are Cat3, Cat4, Cat5, Cat5e, Cat6, and Cat7. CATx is an abbreviation for the category number that defines the performance of building telecommunications cabling as outlined by the Electronic Industries Association (EIA) standards. Some specifications for these categories are shown further down.

Up until the late 1980s thick or thin coaxial cable was typically used for 10-Mbps Ethernet networks, but around that time, UTP cabling became more commonly used because it was easier to install and less expensive. UTP CAT3 and CAT4 were used for a quite limited time since the emergence of 100Base-TX networks meant a quick shift to CAT5. By the year 2000, moves to gigabit (1000Base-TX) Ethernet LANs created a need for another specification, CAT5e. CAT5e is now being superseded by CAT6 cable and there is a developing standard for CAT7.

Organizations such as the Telecommunication Industry Association (TIA) and Electronic Industries

Association (EIA) set specific product standards, and these guidelines have resulted in cables being

classified into various categories based on their performance levels. These are known as category

cables. Each cable differs from other in terms of the type, Bandwidth and thus application as shown:

Table 6: Specifications of CAT 3, 4, 5, 5e, 6 and 7 cables

CAT5 and CAT5e are pretty much the same,CAT5e specification simply included some additional

limits over the CAT5 specification. The reality is that most CAT5 cable is in fact CAT5e cable just not

certified as such. Here is a comparison of those extra specifications.

Table 5: TCP/IP layers and applications

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Table 7: Comparison between CAT 5,5e and 6 cables

Category 6 cable, commonly referred to as Cat 6, is a cable standard for Gigabit Ethernet and other

network physical layers that is backward compatible with the Category 5/5e and Category 3

cable standards. Compared with Cat 5 and Cat 5e, Cat 6 features more stringent specifications

for crosstalk and system noise. The cable standard provides performance of up to 250 MHz and is

suitable for 10BASE-T, 100BASE-TX (Fast Ethernet), 1000BASE-T/1000BASE-TX (Gigabit Ethernet)

and 10GBASE-T (10-Gigabit Ethernet).

Whereas Category 6 cable has a reduced maximum length when used for 10GBASE-T; Category 6a

cable, or Augmented Category 6, is characterized to 500 MHz and has improved alien

crosstalk characteristics, allowing 10GBASE-T to be run for the same distance as previous protocols.

Figure 12: Pin position of a CAT 6 cables

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Category 5 cable (Cat 5) is a twisted pair cable for carrying signals. This type of cable is used

in structured cabling for computer networks such as Ethernet. It is also used to carry other signals

such as telephony and video. The cable is commonly connected using punch down

blocks and modular connectors. Most Category 5 cables are unshielded, relying on the twisted pair

design and differential signalling for noise rejection. Category 5 has been superseded by

the Category 5e (enhanced) specification.

Figure 13: Modular connector of cat 5 cable

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Virtual Local Area Network (VLAN):

A virtual local area network, virtual LAN or VLAN, is a group of hosts with a common set of

requirements, which communicate as if they were attached to the same broadcast domain,

regardless of their physical location. A VLAN has the same attributes as a physical local area

network (LAN), but it allows for end stations to be grouped together even if not on the

same network switch. VLAN membership can be configured through software instead of physically

relocating devices or connections. Most every Enterprise network today uses the concept of virtual

LANs (VLAN). Without VLANs, a switch considers all interfaces on the switch to be in the same

broadcast domain.

To physically replicate the functions of a VLAN would require a separate, parallel collection of

network cables and equipment separate from the primary network. However, unlike a physically

separate network, VLANs must share bandwidth; two separate one-gigabit VLANs that share a single

one-gigabit interconnection can suffer reduced throughput and congestion. It virtualizes VLAN

behaviours (configuring switch ports, tagging frames when entering VLAN, lookup MAC table to

switch/flood frames to trunk links, and untagging when exit from VLAN.)

VLANs are created to provide the segmentation services traditionally provided by routers in LAN

configurations. VLANs address issues such as scalability, security, and network management. Routers

in VLAN topologies provide broadcast filtering, security, address summarization, and traffic flow

management. By definition, switches may not bridge IP traffic between VLANs as it would violate the

integrity of the VLAN broadcast domain.

This is also useful if someone wants to create multiple layer 3 networks on the same layer 2 switch.

For example, if a DHCP server is plugged into a switch it will serve any host on that switch that is

configured to get its IP from a DHCP server. By using VLANs you can easily split the network up so

some hosts won't use that DHCP server and will obtain link-local addresses, or obtain an address

from a different DHCP server.

VLANs are layer 2 constructs, compared with IP subnets, which are layer 3 constructs. In an

environment employing the VLANs, a one-to-one relationship often exists between VLANs and IP

subnets, although it is possible to have multiple subnets on one VLAN. VLANs and IP subnets provide

independent Layer 2 and Layer 3 constructs that map to one another and this correspondence is

useful during the network design process.

By using VLANs, one can control traffic patterns and react quickly to relocations. VLANs provide the

flexibility to adapt to changes in network requirements and allow for simplified administration.

In cloud computing VLANs and IP addresses on them are resources that can be managed by end

users. Placing cloud-based virtual machines on VLANs may be preferable to directly on the Internet

to avoid security issues.

Configuration of VLANs:

We can configure VLAN on a switch or router using many ways like for example using pocket

tracker, HyperTerminal etc.

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The figure below shows how a VLAN is configured using HyperTerminal:

Run HyperTerminal in Windows by going to Start > Programs > Accessories > Communications > HyperTerminal.

After clicking on the HyperTerminal icon, you will see this window:

HyperTerminal prompts you to create a new connection. Note that this is not required but let’s go ahead and do it.

Type in the word Cisco for the connection name and click OK.

Connect your Cisco device to your PC’s COM1 port but don’t turn it on yet. On the next window that appears, make sure that the “Connect Using” field says COM1 and click OK.

Figure 14: HyperTerminal Window

Figure 15: Connect To settings

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On the next window, change the Baud rate to 9600 and click OK.

Now, turn on your Cisco device. In the HyperTerminal window, you should see the boot up process

for your device, like this:

Figure 16: COM 1 port properties

Figure 17: Bios and credential window

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An example showing port 1 and port 48 of Switch-1 and Switch-2 being configured as VLAN with

untagged and tagged modes is shown below:

VLANs are used to connect to a network even when you are physically present at some distant

location. This allows us to access the network even when we are at home or if we are present

another organization or company. Another way of connected to VLANs is by using softwares likes

putty or SSH client.

Figure 18: Setting up VLAN between two switches for a phone and PC

Figure 19: PuTTY command promt

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When do I need a VLAN?

When we have more than 200 devices on your LAN When we have a lot of broadcast traffic on your LAN Groups of users need more security or are being slowed down by too many broadcasts? Groups of users need to be on the same broadcast domain because they are running the same

applications. An example would be a company that has VoIP phones. The users using the phone could be on a different VLAN, not with the regular users.

Or, just to make a single switch into multiple virtual switches. We could also use subnets in our network but the difference between VLAN and subnet is:

VLAN Subnets

Devices are in different physical locations. All devices must be connected to the same switch.

A VLAN is a layer 2 term. A subnet is a layer 3 term.

The configuration is done on server side. Based on client side IP configuration.

The client cannot change it. The client can use any subnet he wants.

VLAN is an isolated portion of the network. It allows segmentation of a network.

It allows tagging and un-tagging of data. This feature is not available in subnet.

VLAN is software based. Subnet is hardware based.

Table 8: VLAN vs. Subnets

Spanning Tree:

The Spanning Tree Protocol (STP) is a network protocol that ensures a loop-free topology for

any bridged Ethernet local area network. The basic function of STP is to prevent bridge loops and

the broadcast radiation that results from them. Loops are formed when two open port in a switch

are connected to each other using an Ethernet cable, this causes uncertainty in the path of the data

transfer and the packet is not transferred to the client efficiently. Spanning tree also allows

a network design to include spare (redundant) links to provide automatic backup paths if an active

link fails, without the danger of bridge loops, or the need for manual enabling/disabling of these

backup links.

Spanning Tree Protocol (STP) is standardized as IEEE 802.1D. As the name suggests, it creates

a spanning tree within a mesh network of connected layer-2 bridges (typically Ethernet switches),

and disables those links that are not part of the spanning tree, leaving a single active path between

any two network nodes.

STP is based on an algorithm invented by Radia Perlman while working for Digital Equipment

Corporation.

The spanning tree algorithm is fed into each switch to automatically prevent the loops.

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A series of diagrams explain the spanning tree processes are shown below:

Figure 20: Assume 3 bridges are connected in the network A,B and C. After the connections are set up every bridge

assumes it is the root making its bridge ID the root ID

Figure 21: The bridge C send it Root ID to the other two bridges which check weather their root ID are less or greater.

Depending on this they select their root.

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Figure 22: Similarly Bridge A also send it root ID to other bridges and thus they all finalize bridge A as root bridge

Figure 23: The root bridge (Bridge A) chooses the Designated and Non-designated port.

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Figure 25: As soon as the flow of BPDUs from Bridge C is interrupted, the Bridge B waits for some duration and

subsequently opens its port 1/2 to forwarding which was blocked earlier. This way spanning tree algorithm is performed.

Figure 24: The BPDUs are sent by Bridge C thus the path is forwarding and the port 1/2.blocked

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Mentor-Mr Narayan Bhagwe

Topic-Wireless Local Area Network

A wireless local area network (WLAN) links two or more devices using some wireless distribution

method (typically spread-spectrum or OFDM radio), and usually providing a connection through an

access point to the wider internet. This gives users the mobility to move around within a local

coverage area and still be connected to the network. Most modern WLANs are based on IEEE

802.11 standards, marketed under the Wi-Fi brand name.

Wireless LANs have become popular in the home due to ease of installation, and in commercial

complexes offering wireless access to their customers; often for free. Large wireless network

projects are being put up in many major cities: New York City, for instance, has begun a pilot

program to provide city workers in all five boroughs of the city with wireless Internet access.]

The major IEEE standards for wireless:

Table 9: IEEE 802.11 WLAN standard and their specification

802.11a

i. The 802.11a standard uses the same data link layer protocol and frame format as the

original standard, but an OFDM based air interface (physical layer). It operates in the 5 GHz

band with a maximum net data rate of 54 Mbit/s, plus error correction code, which yields

realistic net achievable throughput in the mid-20 Mbit/s .

ii. Since the 2.4 GHz band is heavily used to the point of being crowded, using the relatively

unused 5 GHz band gives 802.11a a significant advantage. However, this high carrier

frequency also brings a disadvantage: the effective overall range of 802.11a is less than that

of 802.11b/g. In theory, 802.11a signals are absorbed more readily by walls and other solid

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objects in their path due to their smaller wavelength and, as a result, cannot penetrate as far

as those of 802.11b. In practice, 802.11b typically has a higher range at low speeds (802.11b

will reduce speed to 5 Mbit/s or even 1 Mbit/s at low signal strengths). 802.11a also suffers

from interference, but locally there may be fewer signals to interfere with, resulting in less

interference and better throughput.

802.11b

i. 802.11b has a maximum raw data rate of 11 Mbit/s and uses the same media access

method defined in the original standard. 802.11b products appeared on the market in

early 2000, since 802.11b is a direct extension of the modulation technique defined in the

original standard. The dramatic increase in throughput of 802.11b (compared to the

original standard) along with simultaneous substantial price reductions led to the rapid

acceptance of 802.11b as the definitive wireless LAN technology.

ii. 802.11b devices suffer interference from other products operating in the 2.4 GHz band.

Devices operating in the 2.4 GHz range include: microwave ovens, Bluetooth devices,

baby monitors, and cordless telephones.

802.11g

i. In June 2003, a third modulation standard was ratified: 802.11g. This works in the 2.4 GHz

band (like 802.11b), but uses the sameOFDM based transmission scheme as 802.11a. It

operates at a maximum physical layer bit rate of 54 Mbit/s exclusive of forward error

correction codes, or about 22 Mbit/s average throughputs. 802.11g hardware is fully

backward compatible with 802.11b hardware and therefore is encumbered with legacy

issues that reduce throughput when compared to 802.11a by ~21%.

ii. The then-proposed 802.11g standard was rapidly adopted by consumers starting in January

2003, well before ratification, due to the desire for higher data rates as well as to reductions

in manufacturing costs. By summer 2003, most dual-band 802.11a/b products became dual-

band/tri-mode, supporting a and b/g in a single mobile adapter card or access point. Details

of making b and g work well together occupied much of the lingering technical process; in an

802.11g network, however, activity of an 802.11b participant will reduce the data rate of the

overall 802.11g network.

iii. Like 802.11b, 802.11g devices suffer interference from other products operating in the

2.4 GHz band, for example wireless keyboard

802.11n

i. 802.11n is an amendment which improves upon the previous 802.11 standards by

adding multiple-input multiple-output antennas (MIMO). 802.11n operates on both the

2.4 GHz and the lesser used 5 GHz bands. The IEEE has approved the amendment and it was

published in October 2009. Prior to the final ratification, enterprises were already migrating

to 802.11n networks based on the Wi-Fi Alliance's certification of products conforming to a

2007 draft of the 802.11n proposal.

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The other standards summarized in a tabular form are shown below:

Table 10: Universal 802.11 standards

Thus in order to connect to the Local Area Network (LAN) or to the Internet wirelessly we require

Access points. In computer networking, a wireless access point (WAP) is a device that allows wireless

devices to connect to a wired network using Wi-Fi, Bluetooth or related standards. The WAP usually

connects to a router (via a wired network) if it's a standalone device, or is part of a router itself.

There are many companies which manufacture access points. Some of them are listed below.

1. Siemens

2. Aruba

3. Cisco

4. Ruckus

5. TP Link

6. Huwai

7. D Link

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The image below shows the access points manufacture by Siemens. The above one is a

antenna less PCB based micro strip antenna access point. And the access point below is

with two external antennas.

The specifications of some of the access points manufacture by Siemens are:

Name Range Price

AP 2610 30m 10000

AP 2620 30m 11000

AP 2630 35m 9500

AP 2640 35m 9500

AP 2650 25m 5600

AP 2660 30m 5500

AP 3610 100m 35000

AP 3620 120m 35000 Table 11: Price and range of some access points manufacture by Siemens

Channel and international compatibility:

802.11 divides each of the above-described bands into channels, analogous to the way radio and TV

broadcast bands are sub-divided. For example the 2.4000–2.4835 GHz band is divided into 13

channels spaced 5 MHz apart, with channel 1 centred on 2.412 GHz and 13 on 2.472 GHz (to which

Japan added a 14th channel 12 MHz above channel 13 which was only allowed for 802.11b). 802.11b

was based on DSSS with a total channel width of 22 MHz and did not have steep skirts. Consequently

only three channels do not overlap. Even now, many devices are shipped with channels 1, 6 and 11

Figure 26: Siemens access points

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as preset options even though with the newer 802.11g standard there are four non-overlapping

channels - 1, 5, 9 and 13. There are now four because the OFDM modulated 802.11g channels are

20 MHz wide.

Thus in wireless planning too many companies used access point of channels separated by a factor

of 5. Both the 802.11b and 802.11g have 13 channels and 802.11a has 165 channels. But India we

are allowed to use only 11 channels of every standard. The overlapping of channels other then

channel 1, 6 and 11 is shown below.

Figure 27: Overlapping of channel of 802.11a, 802.11b, and 802.11g standards

Figure 28: Channel 1, 6, and 11 are the non-overlapping channels.

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The wireless frequency bands are broadly classified into two band:

1. ISM- Industrial, scientific and medical radio band. The industrial, scientific and medical (ISM)

radio bands are radio bands (portions of the radio spectrum) reserved internationally for the

use of radio frequency (RF) energy for industrial, scientific and medical purposes other than

communications. Examples of applications in these bands include radio-frequency process

heating, microwave ovens, and medical diathermy machines. There frequency range is from

2.40GHz to 2.48GHz In general, communications equipment operating in these bands must

tolerate any interference generated by ISM equipment, and users have no regulatory

protection from ISM device operation.

2. U-NII- Unlicensed National Information Infrastructure radio band is part of the radio

frequency spectrum used by IEEE-802.11a devices and by many wireless ISPs. It operates

over three ranges:

i. U-NII Low (U-NII-1): 5.15-5.25 GHz. Regulations require use of an integrated antenna. Power

limited to 50mW

ii. U-NII Mid (U-NII-2): 5.25-5.35 GHz. Regulations allow for a user-installable antenna, subject

to Dynamic Frequency Selection(DFS, or radar avoidance).Power limited to 250mW

iii. U-NII Worldwide: 5.47-5.725 GHz. Both outdoor and indoor use, subject to Dynamic

Frequency Selection (DFS, or radar avoidance). Power limited to 250mW. This spectrum was

added by the FCC in 2003 to "align the frequency bands used by U-NII devices in the United

States with bands in other parts of the world". The FCC currently has an interim limitation on

operations on channels which overlap the 5600 - 5650 MHz band.

iv. U-NII Upper (U-NII-3): 5.725 to 5.825 GHz. Sometimes referred to as U-NII / ISM due to

overlap with the ISM band. Regulations allow for a user-installable antenna. Power limited

to 1W

Wireless Security:

Wireless security is the prevention of unauthorized access or damage to computers using

wireless networks. The most common types of wireless security are Wired Equivalent Privacy (WEP)

and Wi-Fi Protected Access (WPA). WEP is one of the least secure forms of security. A network that

is secured with WEP has been cracked in 3 minutes by the FBI.[1]WEP is an old IEEE 802.11 standard

from 1999 which was outdated in 2003 by WPA or Wi-Fi Protected Access. WPA was a quick

alternative to improve security over WEP. The current standard is WPA2; some hardware cannot

support WPA2 without firmware upgrade or replacement. WPA2 uses an encryption device which

encrypts the network with a 256 bit key; the longer key length improves security over WEP.

WPA2 is a WiFi Alliance branded version of the final 802.11i standard. The primary enhancement

over WPA is the inclusion of the AES-CCMP algorithm as a mandatory feature. Both WPA and WPA2

support EAP authentication methods using RADIUS servers and preshared key (PSK).

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Most of the world has switched their WAP from WEP to WPA2, since WEP has been proved too

insecure to be used. It is important to note there is a possible security flaw to the WPA protocol. It is

referred to as Hole196. It is a hole in the protocol that exposes the user to insider attacks.

The access point can be made secured by setting up security by using WEP, WPA, WPAv2 and WPA-

PSK encryption keys which are mostly 128 bits, 256 bits or even 2048 bits. An access point being

configured in such manner is shown below:

Figure 29: Security aspects of WLAN

Figure 30: Wireless security configuration

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Wireless planning:

Planning is a very important part of wireless network as it helps in configuring the signal strength

and the data rate at a particular area. This is not required in Wired or Ethernet connections as the

PCs or clients are directly connected to the switch using Fast or Giga Ethernet cables like Cat5, Cat6

or Cat 6e.

The process of planning is done by the ISP provider according to the customer needs. The points to

be considered before making a survey are:

Minimum cost.

Sufficient bandwidth

Range

Capacity

Output

Directional characteristics of the access point

Height of the access point above the floor.

Access point standard for e.g.:802.11a, g or n.

The composition of the house like walls, windows, door, furniture, lift shafts etc.

Planning is first performed using software and then accordingly the access points are set up as per

the report obtained by the planning.

One of the popularly used software used by many companies is Ekahau Site Survey. It is developed

by Ekahua Inc based in South Korea.

The steps involved in planning are illustrated as follows:

1. Open the map where the site survey is to be conducted using the Ekahau site survey

software.

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2. Now choose the wall type, windows and the door and align them accordingly as shown

below.

We place three access point spaced equally as shown below. The three access point chosen are of 3

different standards 802.11a, 802.11b and 802.11g.Each of three have their own direction, height,

range, power etc.

The signal strength offered by all the three access points must cover the entire the whole are. Thus

the ‘Signal Strength’ parameter helps in understanding the intensity of the signal coverage. This is

illustrated below:

Brick wall (attenuation-10db)

Dry wall (attenuation-3db)

Concrete wall (attenuation-12db)

Figure 31: Ekahau site survey software loaded with sample map

Figure 32: Different types of wall types, window and door frames which can be selected

Figure 33: Signal strength visualization

Access points

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The interference between different access points is another major disadvantage which should be

minimized if not nullified.

As discussed earlier interference is avoided is we choose access points with their channels separated

by a factor of 5. Thus we have used the access point with channel 26, 1 and 11.The interference can

be visualized by using the visualization option and selecting interference in the view menu.

Each type of access point conforming to different standards like 802.11 a, b and g provides different

data rate (bits/sec). The access point of standard b and g provide a data rate of 11 Mbps and

802.11g provides a Data rate of 54Mbps. The image below shows the visualization of the data rate.

The green portion indicates a speed of 11Mbps and the pink portion a speed of 54Mbps. Note that

all the above values are theoretical and practically much lesser.

No interference

Figure 34: Interference visualization for the three access points fixed

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Figure 35: Data rate visualization (Legend-Pink portion-54 Mbps; Green portion-11 Mbps)

Thus in this way the access points are configured and placed to give maximum coverage of the area

and meet the needs of the customer.

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Mentor- Mr. Sagar Punyarthi

Topics-Video Conferencing

Video conferencing is the process by which two parties at any distant location can communicate

with each other through audio as well as video. This help to save time in commuting from one place

and also helps in reducing the carbon footprint.

Video conferencing is the integration of video, audio and peripherals to enable two or more people

to communicate simultaneously over some type of telecommunications lines. By video conferencing

you are transmitting synchronized images and verbal communications between two or more

locations in lieu of them being in the same room.

The main ingredients of video conferencing are video cameras, microphones, appropriate computer

software and computer equipment and peripherals that will integrate with the transmission. The

analogue information recorded by the microphones and cameras is broken down into discreet units,

translating it to ones and zeros. A Codec encodes the information to a digital signal that can then be

transmitted to a codec at the other end, which will retranslate these digital signals back into

analogue video images and audio sounds.

This is now widely used by many companies, organization and even school and colleges for

education, meeting and conferences.

The most popular companies which offer the video conferencing technology equipments are

Polycom, Tandberg, Radvision , Aethra, Huwaie, Life Size and Genesys.

Video conferencing standards:

Like Ethernet and wireless networks, video conferencing also has some defined standards. These

standards are defined by the International Telecommunication Union (ITU) founded in the year

1865.The union developed the standards for video conferencing in the year 1996. They established

Standard H.263 to reduce bandwidth for transmission for low bit rate communication. Other

standards were developed, including H.323 for packet-based multi-media communications. These

are a variety of other telecommunications standards were revised and updated in 1998. In 1999, the

Moving Picture Experts Group as an ISO standard for multimedia content developed Standard

MPEG-4.

ITU standards for video conferencing:

H.320 (synchronous networks)

a. -Video: H.261, H.263, H.264, etc.

b. -Audio: G.711, G.722, G.722.1, G.728.

c. -Data: T.120.

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d. -Call control: H.221.

H.323 (for packet switched networks) H.323 is a multimedia conferencing protocol, which

includes voice, video, and data conferencing, for use over packet-switched networks

a. -Video: H.261, H.263, H.264, etc.

b. -Audio: G.711, G.722, G.729, G.728.

c. -Call setup: H.245, Q.931, RAS.

H.235 for security and encryption.

H.350 (directory based protocol).

H.225 for call signalling.

H.245 for call control.

H.332 for large conferences.

H.450.X is used for supplementary services.

H.235 is used for security and encryption.

H.246 is popularly used for interoperability.

Codecs used for video conferencing:

Video codecs:

1. H.261:

H.261 is a ITU-T video coding standard, ratified in November 1988.[1][2] It is the first member

of the H.26x family of video coding standards in the domain of the ITU-T Video Coding

Experts Group (VCEG), and was the first video codec that was useful in practical terms.

H.261 was originally designed for transmission over ISDN lines on which data rates are

multiples of 64 Kbit/s. The coding algorithm was designed to be able to operate at video bit

rates between 40 kbit/s and 2 Mbit/s. The standard supports two video frame

sizes: CIF(352x288 luma with 176x144 chroma) and QCIF (176x144 with 88x72 chroma) using

a 4:2:0 sampling scheme. It also has a backward-compatible trick for sending still picture

graphics with 704x576 luma resolution and 352x288 chroma resolution (which was added in

a later revision in 1993).

The LGPL-licensed libavcodec includes a H.261 encoder and decoder. It is supported by the

free VLC media player and MPlayermultimedia players, and in ffdshow and FFmpeg decoders

projects

2. H.263:

H.263 is a video compression standard originally designed as a low-bit rate compressed

format for videoconferencing. It was developed by the ITU-T Video Coding Experts

Group (VCEG) in a project ending in 1995/1996 as one member of the H.26x family of video

coding standards in the domain of the ITU-T.

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H.263 has since found many applications on the internet: much Flash Video content (as used

on sites such as YouTube, Google Video, MySpace, etc.) used to be encoded in Sorenson

Spark format (an incomplete implementation of H.263), though many sites now

use VP6 or H.264 encoding. The original version of the RealVideo codec was based on H.263

up until the release of RealVideo 8.

H.263 is a required video codec in ETSI 3GPP technical specifications for IP Multimedia

Subsystem (IMS), Multimedia Messaging Service (MMS) and Transparent end-to-end Packet-

switched Streaming Service (PSS). In 3GPP specifications, H.263 video is usually used

in 3GP container format.

The block layout of the H.263 system is shown below:

Figure 36: The block layout of a H.263 system

3. H.264: The H.264 and the MPEG-4 Part 10, also named Advanced Video Coding (AVC), is

jointly developed by ITU and ISO. H.264/MPEG-4 supports video compression

(coding) for video-conferencing and video-telephony applications. The H.264 video

codec has a very broad range of applications that covers all forms of digital

compressed video from, low bit-rate Internet streaming applications to HDTV

broadcast and Digital Cinema applications with nearly loss less coding.

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APPLICATIONS:

This new standard is designed for technical solutions including the following applications areas:

Broadcast over cable, satellite, Cable Modem, DSL, terrestrial, etc.

Interactive or serial storage on optical and magnetic devices, DVD, etc.

Conversational services over ISDN, Ethernet, LAN, DSL, wireless and mobile networks,

modems, etc. or mixtures of these.

Video-on-demand or multimedia streaming services.

Multimedia Messaging Services (MMS).

BENEFITS

H.264 / MPEG-4 is designed as a simple and straightforward video coding, with enhanced

compression performance, and to provide a “network-friendly” video representation.

H.264/MPEG-4 has achieved a significant improvement in the rate-distortion efficiency –

providing a factor of two in bit-rate savings compared with MPEG-2 Video, which is the most

common standard used for video storage and transmission. The coding gain of H.264 over

H.263 is in the range of 25% to 50%, depends on the types of applications.

Another popular protocols used for video conferencing are SIP and the H.323 protocols.

Figure37: Improved picture quality due to the use of H.264

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H.323 provides a greater Bandwidth and it is used for security and encryption. It has improved

reliability, ad-hoc convenience and centralized management.

Figure 38: H.323 components required for video conferencing

SIP (Session Initiation Protocol):

The Session Initiation Protocol (SIP) is an IETF-defined signaling protocol widely used for

controlling communication sessions such as voice and video calls over Internet Protocol (IP). The

protocol can be used for creating, modifying and terminating two-party (unicast) or multiparty

(multicast) sessions. Sessions may consist of one or several media streams.

Other SIP applications include video conferencing, streaming multimedia distribution, instant

messaging, presence information, file transfer and online games.

The SIP protocol is an Application Layer protocol designed to be independent of the

underlying Transport Layer; it can run on Transmission Control Protocol (TCP), User Datagram

Protocol (UDP), or Stream Control Transmission Protocol (SCTP). It is a text-based protocol,

incorporating many elements of the Hypertext Transfer Protocol (HTTP) and the Simple Mail

Transfer Protocol (SMTP).

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Figure 39: SIP layout

Table 12: Comparison between SIP and H.323

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Polycom provides many types of hardware equipments and software applications for video

conferencing like Polycom PVX and Telepresence.

Polycom PVX:

This software provides features like Picture in

Picture, Desktop sharing, Speed dial and

directory.

Polycom PVX is a full-featured H.323 compliant desktop videoconferencing solution for Microsoft Windows PCs. There is no client currently available for Mac or Solaris. The strength of this package is its quick set-up, ease-in-use and compability with other H.323 clients. Polycom PVX is not a free client (average cost ~$110). A free demo version of the Polycom PVX client is available here. This will allow a user to connect to a videoconference for up to 5 minutes.

Figure 40: Polycom PVX software

Figure 41: Polycom PVX welcome screen

Figure 42: Functions of each key

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Polycom Telepresence m100:

The Telepresence m100 solution is perfect for small and medium businesses that need a cost-

effective way to add video to their communication tools

The Polycom Telepresence m100 business-class video conferencing software application delivers HD-quality audio, video, and content sharing to users of Microsoft Windows OS. Its intuitive and simplified interface lets users search directories for colleagues or friends and click a name to call, discuss projects, and share virtually anything from their desktop with remote participants and teams.

Figure 43: Polycom Telepresence m100 software

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Telepresence:

Telepresence refers to a set of technologies which allow a person to feel as if they were present, to

give the appearance of being present, or to have an effect, via tele-robotics, at a place other than

their true location.

Telepresence requires that the users' senses be provided with such stimuli as to give the feeling of

being in that other location. Additionally, users may be given the ability to affect the remote

location. In this case, the user's position, movements, actions, voice, etc. may be

sensed, transmitted and duplicated in the remote location to bring about this effect.

Therefore information may be travelling in both directions between the user and the remote

location.

Telepresence via video deploys greater technical sophistication and improved fidelity of both sight

and sound than in traditional videoconferencing. Technical advancements in mobile

collaboration have also extended the capabilities of videoconferencing beyond the boardroom for

use with hand-held mobile devices, enabling collaboration independent of location.

Polycom offers a complete portfolio of high definition telepresence solutions over IP networks

ranging from personal telepresence solutions to immersive telepresence solutions. It provides

mainly two services which are the:

Polycom Real Presence Experience (RPX) Series:

Features:

i. HD quality for up to 50% less bandwidth with industry-leading H.264 High Profile support ii. Ideal for executive meetings, board meetings, trainings, education, project management, and

organizations with dispersed workgroups iii. Full screen, cinematic view and seating capacity for 4 to 28 participants creates an immersive

face-to-face meeting experience iv. Transparent technology eliminates distractions and results in more productive meetings v. True-to-life dimensions allow participants to see facial expressions, make eye contact, and

read body language

Figure 44: A telepresence process in progress

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Polycom Open Telepresence Experience (OTX) 100 and 300:

Features:

i. Experience the most stunning HD quality for up to 50% less bandwidth with industry-leading H.264 High Profile support

ii. Transform team collaboration with a unique design and hidden technology for a variety of room uses and "true to life" telepresence meetings

iii. Introduce your organization to real investment protection from standards-based interoperability; connect your teams, your customers, and your partners

iv. Extend the power, performance, and simplicity of native integration with industry-leading UC environments as part of the Polycom Open Collaboration Network strategy

Polycom RMX Platforms

The Polycom RMX 4000, The Polycom RMX 2000 and RMX 1500 are the 3 multi conferencing units manufactured by Polycom which deliver a powerful range of collaboration tools suited to unique individual and team requirements, with open architecture and standards-based designs that provide long-term investment protection and a rational migration path to the future. Polycom RMX 4000:

The Polycom RMX 4000 Conference Platform allows organizations to unite teams over distance in any media. From users in immersive telepresence suites to remote audio callers, the RMX 4000 delivers high quality group communication for increased knowledge sharing and faster team decision making at large organizations. The highest capacity platform in the RMX series, the RMX 4000 natively supports multiple network types to extend the power of unified collaboration within — and beyond — the enterprise. For managing wide-scale conference deployments, the Polycom Distributed Media Application™ (DMA) 7000 pairs with the RMX 4000 and Polycom RMX 2000® to deliver unmatched redundancy, scale, flexibility, and control for conferencing.

Figure 45: Polycom RMX 4000 MC unit

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Polycom RMX 2000 MCU:

Delivers industry-firsts in quality, scale, and flexibility. Unsurpassed scale in a flexible, and future-proof platform. Unrivalled multi-party video quality with support for 1080p and 720p 60fps. Best value per call with flexible or fixed performance capacities. New ease-of-use features simplify conference management. The Polycom RMX 2000 Real-Time Media Conferencing Platform is an advanced IP-based platform for simplified multipoint conferencing. Built upon the Advanced Telecommunications Computing Architecture (Advanced TCA), the standards-based RMX 2000 conferencing platform provides ultra high-speed connectivity, extreme low latency, and the utmost in reliability and serviceability. The RMX 2000 conferencing platform also incorporates a modular, IP Multimedia Subsystem (IMS)-ready design to support highly scalable, next generation deployments of conferencing applications.

Polycom RMX 1500:

A simplified, flexible, mid-range conferencing platform

The Polycom RMX 1500 conferencing platform is designed with intelligence built in—including dynamic resource allocation, network flexibility and reliability, and cost-effective scalability, all tightly integrated with major UC partners. Built on the award-winning Polycom RMX platform, the RMX 1500 extends the power of video, audio, and content collaboration to the network edge.

Figure 46: Polycom RMX 2000 MC unit

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Video Conferencing Management Applications

For every video conferencing terminal setup one also requires some video conferencing

management applications. These are known as Conveyed management application (CAM). Some o

the applications which are provided by Polycom are shown below.

Polycom CMA 5000/4000: Centrally manage and deploy visual communications across your entire organization — desktop to

conference room. Centrally deploy, manage and provision personal and room-based endpoints. Provide corporate directory services to video enabled users Integrated presence-awareness allows users to verify contact availability with status icons The Polycom Converged Management Application (CMA) delivers and manages real-time video conferencing throughout the enterprise. With Polycom CMA, organizations can video-enable individuals and groups in conference rooms, personal workspaces, desktops, and mobile devices using a single highly scalable application. The enterprise benefits from improved communication that speeds decision making and seamlessly extends the power of video to all parts of the organization.

Figure 47: Polycom Conveyed management application

Comparison of CMA 4000 and CMA 5000:

CMA 4000 CMA 5000

1 CPU 2 CPUs

4GB memory 8 GB memory

Single Hard disk RAID (Multiple) Hard disks Table 13: CMA 4000 v. CMA 5000

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An overview of videoconferencing

Figure 48: MCU connections for video conferencing

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References:

Spanning tree-http://www.cisco.com/image/gif/paws/10556/spanning_tree1.swf

www.wikipedia.com

Polycom CMA 5000/4000 and CMA Desktop and Polycom Video Conferencing (VTC)

www.ivci.com

Polycom® OpenTelepresence Experience™ (OTX™) - Products - Polycom ; Polycom

Telepresence Solutions; Polycom® RealPresence® Immersive Theater Solutions - Products -

Polycom

www.polycom.com

www.seimens.in

www.cisco.com

Introduction to VC- Mr. Sagar Punyarthi

Switching NMS-Enterasys