What are advantages and limitations of Wi-Fi?

The Wi-Fi has its own set of advantages and limitations. 

Advantages of WiFi

- WiFi makes the deployment of local Area Networks or LANs quite cheap.  

- There are some areas where the cables cannot be installed such as in historical buildings and outdoor areas. 

- But these spaces do not have any problem in hosting a wireless LAN.  

- Wireless Network adapters are being built into almost all the laptops by the manufacturers.

- A basic level of service is provided at which different brands concerning and client network interfaces access points that are competing with each other can inter-operate. 

- The products that have been certified by Wi-Fi alliance show back word compatibility. 

- A standard device for WiFi will work at any place in the whole world unlike our phones. 

- The WPA2 or the WiFi protected access encryption is secure provided a condition that the pass phrase used is quite strong.  

- The new protocols use for WMM i.e., Quality of service increase the suitability of the Wi-Fi regarding its use in latency - sensitive applications. 

- WMM is a power saving mechanism that is used for extending the life of the battery. 

Limitations of WiFi

- Inconsistency of the operation and spectrum assignments poses a problem worldwide.  

- The range all the WiFi networks is limited. 

- A wireless access point typically uses a stock antenna having a range of 100 m outdoors and 25m indoors.

- The frequency band is a major factor for producing variations in the range.  

- The range of Wi-Fi with a 2.4 ghz frequency block is better when compared with the 5.0 ghz frequency block Wi-Fi. 

- Some wireless routers come with detachable antennas. 

- These antennas can be removed for improving the range. 

- In their place upgraded antennas can be fitted. 

- The benefit of these antennas is that they have high directional gain at the remote devices. 

- The local regulations limit the maximum amount of power that can be transmitted by a Wi-Fi. 

- The power consumption of Wi-Fi is quite higher than the other standards.  

- This is so because of the reach requirements of the wireless LAN applications.

- There are technologies available that provide a propagation range that is much shorter. 

- One such technology is Bluetooth and has very low power consumption.  

- Other technologies such as zigbee have low power consumption, a long range but provides low data rate. 

- The most commonly used wireless encryption standard is WEP or wired equivalent privacy. 

- Even this standard has been proven to be breakable even if correct configuration is used. 

- This problem was addressed by WPA or Wi-Fi protected access standard to some extent. 

- By default the wireless access points use the encryption free mode. 

- The wireless security is disabled because of which the LAN can be openly accessed. 

What are uses of Wifi?

- Routers sometimes act as a Wi-Fi access point incorporating a cable modem or a DSL modem.

- These routers are installed in buildings and homes for providing Internet access and other inter networking services to the devices that in turn are connected to a either through a cable or wireless. 

- Similarly, there are routers that are powered by battery and they consist of a Wi-Fi access point and a mobile Internet radio modem. 

- Today smartphones come with this as a built-in capability.  

- However, this feature is disabled by the carriers. 

- The carriers might charge extra money for this. 

- The standalone facilities are provided by Internet packs. 

- The places where there is no network access, wifi is used. 

- Using Wi-Fi, a direct communication link between two computers can be established.  

- There is no intermediate point.  

- This type of transmission is termed as ad hoc wifi transmission. 

- This network mode is now very popular with the multi-player game consoles. Examples are:

       > Nintendo DS

       > PlayStation portable

       > Digital cameras

       > Other consumer electronic devices.

- A citywide Wi-Fi plan has been implemented by a number of the cities around the world.  

- In India, the first city to do so was Mysore.  

- The first city in the world was Jerusalem.

- The first city in United States was Sunnyvale in California to offer city-wide wifi. 

- Another type of wifi implementation is campus-wide wifi.  

- A number of colleges in United States have set up this kind of wifi network.  

- The first university to have it was Carnegie Mellon University. 

- Using wifi, the local area Network can be deployed in very less cost.  

- There are places where it is not possible for the physical transmission medium such as cables to reach. 

- In such places wifi network is of crucial importance.  

- Also, wifi can be easily deployed in historical buildings and outdoor areas.  

- Now, because of the increasing popularity of the Wi-Fi, the manufacturers are developing Wireless Network adapters for most of the notebooks and laptops.  

- This eventually led to a fall in the price of the Wi-Fi chip set. 

- Today, the Wi-Fi chip set is economically feasible and is included in most of the devices.  

- There are many brands of client network interfaces and access-points that are competing with each other.  

- These interfaces are able to inter-operate at a basic level. 

- The Wi-Fi certification for the products is issued by wifi alliance. 

- This makes them backwards compatible with each other. 

- A standard Wi-Fi Device is supposed to work anywhere in the world. 

- The encryption standard that is considered secure is the WPA2 or wifi protected access.  

- But, this would work only if the pass phrase that is being used is strong enough. 

- The Wi-Fi has been made more suitable with the use of new protocols such as quality of service.  

- This has made wifi compatible with latency sensitive applications.  

- Nowadays, for extending battery life power saving mechanisms such as WMM are being used.  

- These are the major uses of wifi technology.

- The usage wifi has been limited because of its limited range. 

- Therefore, in order to cover up a large area several intermediate Wi-Fi access-points have to be set up. 

- The variations in the range can be produced by varying the frequency band.  

- Wifi with a small frequency block works better than wifi with a larger frequency block.

- Wifi with the larger frequency blocks are optionally used. 

- The power of wifi network can be harnessed by using high gain direction antennas instead of using detachable antennas.  

- Another factor limiting the performance of wifi transmission is the local regulations. 

- Wifi also requires high power to operate upon. 

- This is a cause of concern for the devices' batteries.

What is Wifi technology? How does it work?

- Wifi has emerged as a very popular technology. 

- This technology has enabled the electronic devices to exchange information between them and to share the internet connection without using any cables or wires. 

- It is a wireless technology. 

- This technology works with the help of the radio waves. 

- The Wifi is defined as a WLAN (wireless local area network) product by the wifi alliance that is based on the standards defined by IEEE (802.11 standards). 

- Most of the WLANs are based upon these standards only and so this technology has been named as wifi which is the synonymous with the term WLAN. 

- The wifi-certified trademark might be used by only those wifi products which have the complete certification for the wifi alliance inter-operability. 

- A number of devices now use wifi such as the PCs, smart phones, video game consoles, digital cameras, digital audio players, tablet computers and so on. 

- All these devices can connect to the network and access internet by means of a wireless network access point. 

- Such an access point is more commonly known as a ‘hotspot’. 

- The range of an access point is up to 20 m. 

- But it has a much greater range outside.  

- An access point can be installed in a single room or in an area of many square miles. 

- This can be achieved by using a number of overlapping access points. 

- However, the security of the wifi is less compared to the wired connections for example Internet.

- This is so because a physical connection is not required by an intruder. 

- The web pages using SSL have security but the intruders can easily access the non-encrypted files on the internet. 

- It is because of this, that the various encryption technologies have been adopted by the wifi. 

- The earlier WEP encryption was weak and so was easy to break.

- Later, came the higher quality protocols such as the WPA2 and WPA. 

- The WPS or the wifi protected set up was an optional feature that was added in the year of 2007. 

- This option a very serious flaw which is that it allowed the recovery of the password of the router by an attacker.

- The certification and the test plan has been updated by the wifi alliance for ensuring that there is resistance against attacks in all the devices that have been newly certified.

- For connecting to a wifi LAN, a wireless network interface controller has to be incorporated in to the computer system.

- This combination of the interface controller and the computer is often called as the station. 

- The same radio frequency communication channel is shared by all the stations.

- Also, all the stations receive any transmission on this channel. 

- Also, the user is not informed of the fact that the data was delivered to the recipient and so is termed as the ‘best–effort delivery mechanism’. 

- For transmitting the data packets, a carrier wave is used. 

- These data packets are commonly known as the ‘Ethernet frames’. 

- Each station regularly tunes in to the radio frequency channel for picking up the transmissions that are available. 

- A device that is wifi enabled can connect to the network if it lies in the range of the wireless network. 

- One condition is that the network should have been configured for permitting such a connection. 

- For providing coverage in a large area multiple hotspots are required. 

- For example, wireless mesh networks in London. 

- Through wifi, services can be provided in independent businesses, private homes, public spaces, high street chains and so on. 

- These hotspots have been set up either commercially or free of charge. 

- Free hotspots are provided at hotels, restaurants and airports. 

Explain Border Gateway Protocol (BGP)?

- BGP or Border gateway protocol is the set of rules that is implemented for making the routing decisions at the core of the internet. 

- It involves the use of the IP networks table or we can say prefixes which are used for designating the reach-ability of the network to the autonomous systems. 

- This protocol falls under the category of the path vector protocol or sometimes classified as a variant of the distance vector routing protocols. 

- The metrics of the IGP or the interior gateway protocol are not used by the border gateway protocol rather paths, rule sets or polices are used for making decisions for routing. 

- This is why the border gateway protocol is often called a reach-ability protocol rather than being termed as a routing protocol. 

- The BGP has ultimately replaced the EGP or the exterior gateway protocol. 

- This is so because it allows the full decentralization of the routing process for making transition between the ARPANET model’s core and the decentralized system that consists of a NSFNET backbone and the regional networks associated with it. 

- The present version of the BGP that is being used is the version 4. 

- The earlier versions were discarded for being obsolete. 

- The major advantage is of the classless inter-domain routing and availability of a technique called the route aggregation for making reductions in the routing size. 

- The use of the BGP has made the whole routing system a decentralized system.

- BGP is used by most of the internet service providers for establishing a route between them. 

- This is done especially when the ISPs are multi-homed. 

- That’s why even though it is not used directly by the users; it is still one of the most important protocols in networking. 

- The BGP is used internally by a number of large private IP networks. 

- For example, it is used to combine many large open shortest path first or OSPF networks where these networks do not have the capability to scale to the size by themselves. 

- BGP is also used for multi-homing a network so as to provide a better redundancy. 

- This can be either to many ISPs or to a single ISP’s multi access points. 

- Neighbors of the border gateway protocol are known as the peers. 

- They are created by manually configuring the two routers so as to establish a TCP session on the port. 

- Messages called the 19 byte keep alive messages are sent to the port periodically by the BGP speaker for maintaining the connection. 

- Among the various routing protocols, the most unique is BGP since it relies up on TCP for transporting. 

- When the protocol is implemented in the autonomous system among two peers, it is called IBGP or the internal border gateway protocol. 

- The protocol is termed as the EBGP or the external border gateway protocol when it runs between many autonomous systems.

- Border edge routers are the routers that are implemented on the boundary for exchanging information between various autonomous systems.

- BGP speakers have the capability for negotiating with the session’s option capabilities such as the multi-protocol extensions and a number of recovery modes. 

- The NLRI (network layer reach-ability information) can be prefixed by the BGP speaker if at the time of the creation itself, the multi-protocol extensions are negotiated. 

- The NLRI is advertised along with some address family prefix. 

The family consists of the following:

Ø  IPv4

Ø  IPv6

Ø  Multicast BGP

Ø  IPv4/ IPv6 virtual private networks

- These days the border gateway protocol is being commonly employed as the generalized signaling protocol whose purpose is to carry information via the routes that might not form the global internet’s part. 

Explain the concept of inter-networking?

- The practice in which one computer network is connected with the other networks is called inter-networking. 

- The networks are connected with the help of gateways. 

- These gateways are used since they offer a common method for routing the data packets across the networks.

- The resulting system in which a number of networks are connected is called the inter-network or more commonly as the internet. 

- The terms “inter” and “networking” combine together to form the term “internet working”.  

- Internet is the best and the most popular example of the inter networking. 

- Internet has formed as a result of many networks connected with the help of numerous technologies. 

- Many types of hardware technologies underlie the internet. 

- The internet protocol suite (IP suite) is the inter networking protocol standard responsible for unifying the diverse networks. 

- This protocol is more commonly known as the TCP/ IP. 

- Two computer local area networks (LANs) connected to one another by means of a router form the smallest internet but not the inter network. 

- Inter networking is not formed by simply connecting two LANs together via a hub or a switch. 

- This is called expansion of the original local area network. 

- Inter networking was started as a means for connecting the disparate networking technologies. 

- Eventually, it gained widespread popularity because of the development needs of connecting many local area networks together through some kind of WAN (wide area network). 

- “Catenet” was the original term that was used for the inter network. 

- Inter network includes many types of other networks such as the PAN or personal area network. 

- Gateways were the network elements that were originally used for connecting various networks in predecessor of the internet called the ARPANET. 

- Today, these connecting devices are more commonly known as the internet routers. 

- There is a type of interconnection between the various networks at the link layer of the networking model. 

- This layer is particularly known as the hardware centric layer and it lies below the TCP/ IP logical interfaces level. 

Two devices are mainly used in establishing this interconnection:

Ø  Network switches and

Ø  Network bridges

- Even now this cannot be called as inter networking rather, the system is just a single and large sub-network. 

- Further, for traversing these devices no inter networking protocol is required. 

- However, it is possible to convert a single network in to an inter network. 

- This can be done by making various segments out of the network and also making logical divisions of the segment traffic using the routers. 

- The internet protocol suite has been particularly designed for providing a packet service. 

- This packet service offered by the IPS is quite unreliable. 

- The elements that maintain a network state and are intermediate in the network are avoided by the architecture. 

- The focus of the architecture is more on the end points of the active communication session.

- For a reliable transfer of the data, a proper transport layer protocol must be used by the applications. 

- One such protocol is the TCP (transmission control protocol) and it is capable of providing a reliable stream for communication. 

- Sometimes a simpler protocol such as the UDP (user datagram protocol) might be used by the applications. 

- The applications using this protocol carry out only those tasks for which reliable data delivery is not required or for which realtime is required. 

Examples of such tasks include voice chat or watching a video online etc. Inter networking uses two architectural models namely:

1. OSI or the open system interconnection model: This model comes with 7 layer architecture that covers the hardware and the software interface.
2. TCP/ IP model: The architecture of this model is somewhat loosely defined when compared with the OSI model. 

What are different methods of broadcasting a packet?

Without broadcasting, our information theory and telecommunications does not mean anything. 

- It is broadcasting that actually makes the transfer of data possible from one point to another. 

- Broadcasting can be defined as the method of transfer of a message to a number of recipients, all at the same time. 

- Broadcasting is often considered to be a sort of high – level operation in some programs while low level operation in some other programs. 

- For example, in message passing interface, broadcasting is a high level operation whereas in broadcasting on Ethernet, it is considered to be a low level operation in networking. 

We have many kinds of routing schemes suiting for various kinds of broadcasting requirements:

1. Anycast
2. Broadcast
3. Multicast
4. Unicast
5. Geocast

- Broadcasting is transmission of a packet to each and every device that is attached to the network. 

- However, the broadcasting is limited to transmission in the broadcast domain in practical applications. 

- Broadcasting can be contrasted with uni cast routing scheme in the sense that in uni cast, the datagrams are transmitted by one host and are received by another single host only. 

- This receiving host is identified with an IP address on the network that is unique to it. 

- All the technologies used in networking are not capable of supporting broadcasting. 

For example, the following do not have this capability:

Ø  X.25 relay

Ø  Frame relay

- The broadcast method cannot be implement with IPv6 i.e., the successor of the IPv4 (internet protocol version 4).

- This is for the avoidance of the disturbance to the nodes. 

- Also, there does not exist anything such as the internet wide broadcast. 

- Therefore, this limits the scope of the broadcasting to the LAN technologies such as token ring and Ethernet since here the impact of the broadcasting performance is small.

Categories of Broadcasting Methods

The broadcasting methods can be classified in to 4 major categories as per the IEEE 802.11 standard:

1. Simple flooding method: 

- In this method the packets are rebroadcast-ed by each of the nodes.

- A message is disseminated to all the neighboring nodes by a source node in the MANET. 

- If the neighboring nodes would have received this message already, then this time the message will be dropped.

- If not, they will re-disseminate the message to their neighbors simultaneously. 

- This process continues until all the nodes have received this message. 

- Only for a MANET this method proves to be reliable that too only if the nodes have low density as well as high mobility. 

- This method has a good potential for harming the network and make it unproductive. 

- This happens so because it will cause congestion in the network thereby exhausting the power of the battery.

2. Area based broadcasting method: 

- Here, we assume a transmission distance.

- Only if sufficient coverage area is detected, the node can rebroadcast otherwise not. 

- This method can be of two types namely location based scheme and the distance based scheme.

3. Probability tested: 

- Rebroadcasting is done by the nodes depending up on the network’s topology and probabilities assigned to them. 

- This somewhat resembles the flooding algorithm with the only exception that a predetermined probability is used for rebroadcasting by the nodes.

- The transmission coverage might be shared by the multiple nodes where the network is too dense.

4. Neighborhood based broadcasting method: 

- Neighborhood method is used for maintaining a state in the neighborhood and rebroadcasting is done with the help of the info obtained from the nodes in this neighboring area. 

- There are two types of this method namely self-pruning approach and ad hoc broadcasting approach.      

Explain the concept of piggybacking?

- Piggybacking is a well known technique used in the transmission of data in the third layer of the OSI model i.e., the network layer. 

- It is employed in making a majority of the frames that are transmitted from receiver to the emitter. 

- It adds to the data frame, the confirmation that the sender sent on successful delivery of data frame. 

- This confirmation is called the ACK or acknowledge signal. 

- Practically, this ACK signal is piggybacked on the data frame rather than sending it individually by some other means. 

Principle behind Piggybacking

- The piggybacking technique should not be confused with the sliding window protocols that are also employed in the OSI model. 

- In piggybacking, an additional field for the ACK or the acknowledgement signal is incorporated in to the data frame itself. 

- There is only a difference of bit between the sliding window protocol and piggybacking.

- Whenever some data has to be sent from party to another, the data will be sent along with the field for ACK. 

The piggybacking data transfer is governed by the following three rules:

Ø  If both the data as well as the acknowledgement have to be sent by the party A, it has to include both the fields in the same frame.

Ø  If only the acknowledgement has to be sent by the party A, then it will have use a separate frame i.e., an ACK for that.

Ø  If only the data has to be by the party A, then the ACK field will be included within the data frame and thus transmitted along with it. This duplicate ACK frame is simply ignored by the receiving party B.

- The only advantage of using this technique is that it helps in improving efficiency. 

- The disadvantage is that is the service can be blocked or jammed by the receiving party if there is no data to be transmitted. 

- Enabling a receiver timeout by means of a counter the moment when the party receives the data frame can solve this problem to a great extent. 

- An ACK control frame will be sent by the receiver if the timeout occurs and still there is no data for transfer. 

- A counter called the emitter timeout is also set up by the sender which if ends without getting any confirmation from the receiver will make the sender assume that the data packet got lost in the way and therefore will have to re-transmitted.

- Piggybacking is also used in accessing the internet.

- It is used in establishment of a wireless internet connection by means of wireless internet access service of the subscriber without taking explicit permission from the subscriber. 

- However, according to the various jurisdiction laws around the world, this practice is under ethical and legal controversy. 

- In some places it is completely regulated or outlawed while at other places it is allowed.  

- A business customer who provides services related to hotspots, as of cafe and hotels, cannot be thought of using piggybacking technique via non – customers. - A number of such locations provide services for a fee. 

What are the risks and liabilities with instant messaging?

There are a number of risks and liabilities associated with Instant Messaging. Till today several attempts have been done in order to create a unified IM standard. 

Few have been mentioned below:

1. Session initiation protocol or SIP of IETF.
2. SIP for instant messaging and presence leveraging extensions or SIMPLE.
3. APEX or application exchange.
4. IMPP or instant messaging and presence protocol.
5. XMPP or open XML – based extensible messaging and presence protocol.
6. Instant messaging and presence service of open mobile alliance (this one was developed exclusively for the mobiles.)

Although a number of benefits are given by instant message, there are also many risks and liabilities associated with it. This happens particularly when one uses IM at his/ her workplace. 

Associated risks and liabilities are:

1. Security risks
2. Inappropriate use
3. Compliance risks
4. Trade secret leakage

About Security Risks

- Security risks involve infecting the systems with viruses, worms, spyware and Trojans etc.

- Hackers and crackers make use of IM vectors for making phishing attempts, introducing the file attachments laden with virus and poisoned URLs. 

- Two main methods are used by the hackers for delivering the malicious code via instant messaging:

1. Delivering viruses, spyware or Trojan horses through an infected file.
2. Using the socially engineered text that has a web address enticing the recipient to go to an URL that in turn connects him/ her to a malicious website.

- The first kind of means i.e., the Trojans, worms and viruses propagate themselves by infecting the whole contact list of the user. 

- An attack done through means of a poisoned URL may infect 1000s of user’s system in a very short duration i.e., just when each of the person in the user’s contact list receives a message that appears to be from a trusted source. 

- Thus, when the recipients click on the web address, the whole cycle repeats. - Such infections might be for some criminal or a nuisance reasons. 

- These attacks are getting more sophisticated with time. 

- The connections in the instant messaging are usually in plain text. 

- This is what that makes them vulnerable to threats such as eavesdropping. 

- Also, with instant messaging, the UDP ports are left exposed to the world inviting many potential security vulnerabilities and raising many security issues.

About Inappropriate Use

 

- All the organizations, be of any type need protection against the liability of the inappropriate use of the IM service by the employees. 

- The nature of the IM, be it immediate, informal or anonymous marks it as an abuse of the workplace. 

- In a number of nations, a legal responsibility has been set up by the corporations in order to make sure that the working environment is free of any harassment for the employees. 

- Instant messaging is now included as an integral part of the policies of the companies regarding the appropriate use of services such as e – mail and world wide web and some other corporate assets.

About Compliance Risks

- Using the IM services at workplace also induces a risk concerning the non – compliance to laws and regulations that govern the use of electric communications. 

- The need for the production of the archived business communications that would satisfy the judicial requests is what to which most of the common regulations is related to. 

- There are a number of IM communications falling under the category of business communications and are retrievable.