What are uses of WiMax technology?

- The WiMax technology has been used since a long time to provide assistance to the communication process.

- This area has seen major deployment of wimax technology especially in Indonesia during the calamity of tsunami in the year of 2004. 

- The WiMax technology brought in the possibilities of providing broadband access that helped a big deal in regeneration of the communication. 

- The organizations such as FEMA and FCC (federal communications commission) felt the need of wimax in their communication process. 

- The WiMax applications with high efficiency are available today.

- It is known to offer a broad base for the customers and the services had been improved by adding mobility feature to them.

- The service providers use the WiMax technology for providing various services such as mobile and Internet access, voice, video and data. 

There are other advantages of using wimax technology.  

- You get to save a lot of prospective cost and at the same time you get efficiency in services.

- It is even capable of allowing the video making, VOIP calling and data transfers at high speeds.

- The mobile community has been upgraded so much with the coming of the WiMax technology.

- However, there are three main applications offered by WiMax namely backhaul, consumer connectivity and business.

- The real augmentation has been drawn to communications through WiMax technology because of which they can benefit both from the data transmission and video apart from voice. 

- This has facilitated quick response from the applications as per the situation.  

- A temporary communication services can be deployed by a client using WiMax technology.

- It can even speed up the network according to the circumstances and events.  

- This has got us access to visitors, employees and media on a temporary basis.  

- If we are located in the range of the tower, it is quite easy for us to gain access to the equipment of the premises of for the events.

The factors that make the wimax technology so powerful are the following:

> high bandwidth

> high quality services

> security

> deployment

> full duplex consisting of DSL

> reasonable cost

For some applications, the wimax technology is used exclusively as in the following:

1. A means of connecting for the small and medium sized businesses.  - This technology has enabled these businesses to progress day by day.

- The connectivity offered by WiMax technology is good enough to attract clients.  

- It then provides them a number of services such as that of hotspots and so on.  

- Therefore, this application has gotten into spot light.

2. Backhaul

- The most important application of the WiMax technology is the range.

- This is so because using WiMax tower can be used as a means to connect with the other WiMax towers through line-of-sight communication which involves using microwave links. 

- This connectivity between two towers is called as backhaul.  

- It is capable of covering up to 3000 miles. 

- The WiMax network is even sufficient for covering remote and rural areas.

3. The nomadic broadband is another application of wimax technology which can be considered as an extended plan of wifi.

- The access points provided by WiMax technology might be less in number but they offer very high security.  

- Many companies use the WiMax base station for the development of the business.

What is WiMax technology?

Worldwide inter-operability for microwave access or wimax is standard developed for wireless communications that has been designed so as to deliver data rates of 30-40 mbps. The update in the technology in the year 2011 upgraded the technology to provide around 1 gbps for the stations that were fixed. 

- The Wimax forum is responsible for naming the technology as Wimax. 

- This forum was formed in the year of 2001 for the promotion of the inter-operability and conformity of this standard. 

- The Wimax has been defined by the forum as the technology based up on standards that enable the last mile wireless broadband delivery as alternative for the DSL and the cable thing. 

- The IEEE 802/ 16’s interoperability implementations are referred to as the WiMax. 

- The wimax forum has ratified this family of standards. 

- By virtue of the certification provided by this forum, the vendors are able to sell mobile and fixed products that are wimax certified. 

- This is done for ensuring that a level of inter-operability is maintained at par with the other products that have been also certified for the same profile. 

- The ‘fixed wimax’ is the name given to the original IEEE 802.16 standards.

- ‘Wifi on steroids’ is the term used to refer to WiMax sometimes. 

It has got a number of applications such as in:

Ø  Broadband connections

Ø  Cellular back-haul

Ø  Hot spots and so on.

- This technology shares some similarity with the Wifi technology however, this one is more capable of transmitting data at greater distances.

It is because of its range and bandwidth that the WiMax is suitable for the following applications:

Ø  Provides services such as the IPTV services and VoIP (telecommunications services).

Ø  Provides mobile broadband connectivity that is portable across the cities and countries and that can be accessed via different kinds of devices.

Ø  Provides an alternative for DSL and cable in the form of wireless last mile broadband access.

Ø  Acts as a source of internet connectivity.

Ø  Metering and smart grids.

- This technology can be used at home for providing internet access across the countries. 

- This has also caused a rise in the market competition. 

- The WiMax is even economically feasible. 

- Mobile wimax has been used as a replacement for the technologies like CDMA, GSM that are cellular phone technologies.  

- The technology has also been used as an overlay for increasing the capacity.  

- The fixed wimax is now used for 2g, 3g and 4g networks as a wireless back-haul technology in almost all the nations whether they are developed or developing.  

- In some states of North America, this technology is provided through a numbered of copper wire line connections. 

- On the other hand, the technology is back hauled via satellites in case of the remote cellular operations.  

- While in other cases even microwave Links are used. 

- The bandwidth requirements of the WiMAX demand more substantial back-haul when compared to other legacy cellular applications. 

- In some of the cases, the sites have been aggregated by the operators by use of Wireless Technology.  

- The traffic is then introduced to the fiber networks as per the convenience.  

- The technologies that provide triple play services are directed compatible with the WiMAX.  

- These services might include multi-casting and quality of service. 

- WiMax has been widely used for providing assistance in the communications. 

- The Intel Corporation has donated the hardware for WiMax technology for assisting the FCC (federal communications commission) and FEMA etc.

- The subscribers’ stations or SS are the devices which are used for connecting to a WiMAX Network. 

- These devices might be portable such as the following:

      > Handsets and smart phones

      > PC peripheral such as USB dongles, PC Cards and so on. 

      > Embedded devices in notebooks.

What are the parameters of QoS - Quality of Service?

With the arrival of the new technologies, applications and services in the field of networking, the competition is rising rapidly. Each of these technologies, services and applications are developed with an aim of delivering QoS (quality of service) that is either better with the legacy equipment or better than that. The network operators and the service providers follow from trusted brands. Maintenance of these brands is of critical importance to the business of these providers and operators. The biggest challenge here is to put the technology to work in such a way that all the expectations of the customers for the availability, reliability and quality are met and at the same time the flexibility for quick adaptation of the new techniques is offered to the network operators. 

What is Quality of Service?

- The quality of service is defined by its certain parameters which play a key role in the acceptance of the new technologies. 

- The organization working on several specifications of QoS is ETSI.

- The organization has been actively participating in the organization of the inter-operability events regarding the speech quality.

- The importance of the QoS parameters has been increasing ever since the increasing inter-connectivity of the networks and interaction between many service providers and network operators for delivering communication services.

- It is the quality of service that grants you the ability for the making parameters specifications based up on multiple queues in order to shoot up the performance as well as the throughput of wireless traffic as in VoIP (voice over internet), streaming media including audio and video of different types. 

- This is also done for usual IP over the access points.

- Configuration of the quality of service on these access points involves setting many parameters on the queues that are already there for various types of wireless traffic. 

- The minimum as well as the maximum wait times are also specified for the transmission. 

- This is done through the contention windows. 

- The flow of the traffic between the access point and the client station is affected by the EDCA (AP enhanced distributed channel access) parameters. 

- The traffic flow from client to the access point is controlled by the station enhanced distribution channel access parameters. 

Below we mention some parameters:

Ø  QoS preset: The options listed by the QoS are WFA defaults, optimized for voice, custom and WFA defaults.

Ø  Queue: For different types of data transmissions between AP – to – client station, different queues are defined:

- Voice (data 0): Queue with minimum delay and high priority. Data which is time sensitive such as the streaming media and the VoIP are automatically put in this queue.

- Video (data 1): Queue with minimum delay and high priority. Video data which is time sensitive is put in to this queue automatically.

- Best effort (data 2): Queue with medium delay and throughput and medium priority. This queue holds all the traditional IP data. 

- Background (data 3): Queue with high throughput and lowest priority. Data which is bulky, requires high throughput and is not time sensitive such as the FTP data is queued up here.

Ø AIFS (inter-frame space): This puts a limit on the waiting time of the data frames. The measurement of this time is taken in terms of the slots. The valid values lie in the range of 1 to 255.

Ø Minimum contention window (cwMin): This QoS parameter is supplied as input to the algorithm for determining the random back off wait time for re-transmission.

Ø cwMax

Ø maximum burst

Ø wi – fi multimedia

Ø TXOP limit

Ø Bandwidth

Ø Variation in delay

Ø Synchronization

Ø Cell error ratio

Ø Cell loss ratio

What is meant by Quality of Service provided by network layer?

- The QoS or the quality of service is such a parameter that refers to a number of aspects of computer networks, telephony etc. 

- This parameter allows transportation of traffic as per some specific requirements. 

- Technology has advanced so much now computer networks can also be doubled up as the telephone networks for doing audio conversations. 

- The technology even supports the applications which have strict service demands. 

- The ITU defines the quality of service in telephony. 

It covers all the requirements concerning all the connection’s aspects such as the following:

Ø  Service response time

Ø  Loss

Ø  Signal – to – noise ratio

Ø  Cross – talk

Ø  Echo

Ø  Interrupts

Ø  Frequency response

Ø  Loudness levels etc.  

- The GoS (grade of service) requirement is one subset of the QoS and consists of those aspects of the connection that relate to its coverage as well as capacity. 

- For example, outage probability, maximum blocking probability and so on. 

- In the case of the packet switched telecommunication networks and computer networking, the resource reservation mechanisms come under the concept of traffic engineering. 

- QoS can be defined as the ability by virtue of which the different applications, data flows and users can be provided with different priorities. 

- It is important to have QoS guarantees if the capacity of the network is quite insufficient. 

- For example, voice over IP, IP-TV and so on. 

- All these services are sensitive to delays, have fixed bit rates and have limited capacities.

- The protocol or network supporting the QoS might agree up on some traffic contract with the network node’s reserve capacity and the software. 

- However, the quality of service is not supported by the best effort services. 

-Providing high quality communication over such networks provides a alternative to the QoS control mechanisms that are complex. 

- This happens when the capacity is over-provisioned so much that it becomes sufficient for the peak traffic load that has been expected. 

- Now since the network congestion problems have been eliminated, the QoS mechanisms are also not required. 

- It might be sometimes be taken as the level of the service’s quality i.e., the GoS. 

- For example, low bit error probability, low latency, and high bit rate and so on. 

- QoS can also be defined as a metric that reflects up on the experienced quality of the service.

- It is the cumulative effect that can be accepted. 

Certain types of the network traffic require a defined QoS such as the following:

Ø  Streaming media such as IPTV (internet protocol television), audio over Ethernet, audio over IP etc.

Ø  Voice over IP

Ø  Video conferencing

Ø  Telepresence

Ø  iSCSI, FCoE tec. Storage applications

Ø  safety critical applications

Ø  circuit emulation service

Ø  network operations support systems

Ø  industrial control systems

Ø  online games

- All the above mentioned services are examples of the inelastic services and a certain level of latency and bandwidth is required for them to operate properly. - On the other hand, the opposite kind of services such as the elastic services can work with any level of bandwidth and latency. 

- An example of these type of services is the bulk file transfer application based up on TCP.

- A number of factors affect the quality of service in the packet switched networks. 

- These factors can be broadly classified in to two categories namely technical and the human factors. 

The following factors are counted as the human factors:

Ø  reliability

Ø  scalability

Ø  effectiveness

Ø  maintainability

Ø  grade of service and so on.

- ATM (asynchronous transfer mode) or GSM like voice transmissions in the circuit switched networks have QoS in their core protocol. 

What are the services provided to upper layers by transport layer?

In the field of computer networking, the purpose of the 4^th layer or the transport layer is to provide services for the end to end communication for the various operating applications. The services are provided within an architectural framework that consists of protocols and the components and is layered. It also offers convenient services such as the following:

Ø  Connection – oriented data stream support

Ø  Reliability

Ø  Flow control

Ø  Multiplexing and so on.

- Both the OSI (open systems interconnection) and TCP/ IP model include the transport layer. 

- The foundation of the internet is based up on the TCP/ IP model whereas for the general networking, the OSI model is followed. 

- However, the transport layer is defined differently in both of these models. Here we shall discuss about the transport layer in the TCP model since it is used for keeping the API (application programming interface) convenient to the internet hosts. 

- This is in contrast with the definition of the transport layer in the OSI model. 

- TCP (transmission control protocol) is the most widely used transport protocol and so the internet protocol suite has been named after it i.e., the TCP/ IP. 

- It is a connection-oriented transmission protocol and so it is quite complex. 

- This is also because it incorporates reliable data stream and transmission services in to its state-ful design. 

- Not only TCP there are other protocols in the same category such as the SCTP (stream control transmission protocol) and DCCP (datagram congestion control protocol).

Now let us see what all services are provided by the transport layer to its upper layers:

ØConnection-oriented communication: It is quite easy for the application for interpreting the connection as a data stream instead of having to cope up with the connectionless models that underlie it. For example, internet protocol (IP) and the UDP’s datagram protocol.

Ø Byte orientation: Processing the data stream is quite easy when compared with using the communication system format for processing the messages. Because of such simplification, it becomes possible for the applications to work up on message formats that underlie.

Ø  Same order delivery: Usually, it is not guaranteed by the transport layer that the data packets will be received in the same order in which they were sent. But this is one of the desired features of the transport layer. Segment numbering is used for incorporating this feature. The data packets are thus passed on to the receiver in order. Head of line blocking is a consequence of implementing this.

Ø  Reliability: During the transportation some data packets might be lost because of errors and problems such as network congestion. By using error detection mechanism such as CRC (cyclic redundancy check), the data might be checked by the transport protocol for any corruption and for the verification whether the correct reception of the data by either sending a NACK or an ACK signal to the sending host. Some schemes such as the ARR (automatic repeat request) are sometimes used for the retransmission of the corrupted or the lost data.

Ø  Flow control: The rate with which the data is transmitted between two nodes is managed for preventing a sending host with a fast speed from the transmission of data more than what the receiver’s data buffer can take at a time. Otherwise it might cause a buffer overrun.

Ø  Congestion avoidance: Traffic entry in to the network can be controlled by means of congestion control by avoiding congestive collapse. The network might be kept in a state of congestive collapse by automatic repeat requests. 

What are the reasons for using layered protocols?

Layered protocols are typically used in the field of networking technology. There are two main reasons for using the layered protocols and these are:

1. Specialization and
2. Abstraction

- A neutral standard is created by a protocol which can be used by the rival companies for creating programs that are compatible. 

- So many protocols are required in the field and that should also be organized properly and these protocols have to be directed to the specialists that can work up on these protocols. 

- A network program can be created using the layered protocols by a software house if the guidelines of one layer are known. 

- The services of the lower level protocols can be provided by the companies. 

- This helps them to specialize. 

- In abstraction, it is assumed that another protocol will provide the lower services. 

- A conceptual framework is provided by the layered protocol architecture that divides the complex task of information exchange into much simpler tasks between the hosts. 

- The responsibility for each of the protocols is narrowly defined. 

- A protocol provides an interface for the successive higher layer protocol. 

- As a result of this, it goes in to hiding the details of the higher protocol layers that underlies. 

- The advantage of using the layered protocols is that the same application i.e., the user level program can be used by a number of diverse communication networks.

- For example, when you are connected to a dial up line or internet via LAN you can use the same browser. 

- For simplifying the networking designs, one of the most common techniques used is the protocol layering. 

- The networking designs are divided in to various functional layers and the protocols are assigned for carrying out the tasks of each layer. 

- It is quite common to keep the functions of the data delivery separate from each other and separate layers for the connection management too.  

- Therefore, we have one protocol for performing the data delivery tasks and second one for performing connection management. 

- The second one is layered up on the first one. 

- Since the connection management protocol is not concerned with the data delivery, it is also quite simple. 

- The OSI seven layer model and the DoD model are one of the most important layered protocols ever designed. 

- A fusion of both the models is represented by the modern internet. 

- Simple protocols are produced by the protocol layering with some well defined tasks. 

- These protocols then can be put together to be used as a new whole protocol. - As required for some particular applications, the individual protocols can be either replaced or removed. 

- Networking is such a field involving programmers, electricians, mathematicians, designers, electricians and so on. 

- People from these various fields have very less in common and it is because of the layering that people with such varying skills to make an assumption or feel like others are carrying out their duty. 

- This is what we call abstraction. 

- Protocols at a level can be followed by an application programmer via abstraction assuming that network exists and similarly electricians assume and do their work. 

- One layer can provide services to the succeeding layer and can get services in return too. 

- Abstraction is thus the fundamental foundation for layering. 

- Stack has been used for representing the networking protocols since the start of network engineering. 

- Without stack, it would be unmanageable as well as overwhelming. 

- Representing the layers of specialization for the first protocols derived from TCP/ IP.

Give advantages of frame relay over a leased phone line?

Frame relay and leased phone lines are two of the physical connection media for setting up the connections. 

Advantages of Frame Relay over Leased Phone Line

- Frame relay is a kind of the standardized WAN (wide area network) technology for specifying the logical link as well as physical link layers of the digital telecommunication channels. 

- It is done by the means of a packet switching methodology.

- The frame relay technology has been designed for transportation across the ISDN (integrated services digital network) infrastructure. 

- Today, it is used in the context of a number of network interfaces. 

- Frame relays are commonly implemented for VoFR (voice over frame relay).  - It is used as an encapsulation technique for the data. 

- The frame relays are used between the WANs and the LANS.

- A private line or a leased line is provided to the user that connects to the frame relay node. 

- The frequently changing path is transparent to the WAN protocols used extensively by the end users. 

- Data is transmitted via these networks and the frame relay network handles all this.

- One advantage of the frame relays over the leased lines is that they are less expensive and this is what that makes the frame relays so popular in the telecommunications industry.

- Another advantage of the frame relays over the leased lines that make them popular is that they have user equipment that can be configured with extreme simplicity in the frame relay network. 

- The usage of the Ethernet over the fiber optics communication is high. 

- This has led to using the frame relay protocol and encapsulation by the dedicated broadband services like DSL and cable modem, VPN, MPLS etc. 

- However, there are a number of rural regions in India where there is still an absence of the cable modem and DSL services.

- In such areas, the only option for the non-dial-up connection is the frame relay line of 64 Kbit/ s.

- Thus, it might be used by some retail chain to connect with the WAN of their corporate. 

- The aim of the designers of the frame relay is to offer a telecommunication service for transmitting the cost efficient data between the various end points in the WAN and the local area networks in an intermittent traffic. 

- The data is put in to units of variable sizes called the frames by the frame relay process. 

- The required error correction process is left up to the end points. 

- This error correction includes re-transmission of the data. 

- This increases the speed of the overall transmission of data. 

- A PVC or the permanent virtual circuit is provided by the network so that when a customer looks at a dedicated connection and not having to pay for leased line that is full time engaged. 

- The route by which each frame travels to the destined end point is figured out by the service provider and thus he decides the charges based up on the usage. 

- A level of the service quality can be selected by the enterprise. 

- The frames can be prioritized while the importance of the other frames is reduced. 

- The frame relay can run on systems such as the following:

Ø  Fractional T – 1

Ø  Full T – carrier

Ø  E – 1

Ø  Full E carrier

- A frame relay provides mid-range services between ATM (asynchronous transfer mode) and the ISDN operating at a speed of 128 Kbps. 

- Not only it provides the services, it also complements them. 

- The base of the frame relay technology is provided by the X.25 packet switching that has been designed for data transmission over the analog voice lines.