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 Traditional Cryptography?

- Cryptography is the practice that involves study and application of the techniques for making communication secure with the adversaries or the third parties. 

To be more general, it involves construction and the analyzation of the protocols for overcoming the impact of the adversaries and other aspects concerning the information security such as the following:

Ø  Data confidentiality

Ø  Data integrity

Ø  Authentication

Ø  Non – repudiation

- The modern cryptography in contrast to the traditional cryptography intersects the computer science, mathematical and the engineering disciplines. 

There are various applications of cryptography as in the following:

Ø  ATM cards

Ø  Computer passwords

Ø  Electronic commerce

- The traditional cryptography was synonymous with the process of encryption which involves converting the information which is in readable state to such a state in which it appears like utter nonsense. 

- The one who generated the encrypted message also shared the technique for decoding the message only with the desired recipients, thus the unwanted people are precluded from doing so.

- Cryptography is in use since the World War I and the methods that were used then now have become so complex and eventually its application increased. 

- Modern cryptography’s foundation is based up on the computer science and the mathematical theory. 

- The designing of the cryptographic algorithms is done around the computational hardness assumptions. 

- In practice, this makes these algorithms quite hard to break by any third party. 

- However, theoretically it is possible to break in to such a system but for doing so any known practical means are in-feasible.

- That is why, all these schemes are considered to be computationally safe and secure. 

For the following, the continuous adaptation of these methods is required:

Ø  Improvements in the algorithms for the integer factorization.

Ø  Faster computing technology.

- Also, there are schemes that are information – theoretically secure and even with unlimited computing power, these schemes cannot be broken.

- One such scheme is one time pad. 

- Also, the implementation of these schemes is also quite difficult when compared to the schemes that are computationally secure but are theoretically breakable. 

- Traditionally cryptography referred only to the encryption which involves conversion of the ordinary info in to cipher text or unintelligible text. 

- The reverse process of this is decryption. 

- The pair of algorithms that carry out these two processes is called the cipher. - Each instance of the operation of the cipher is controlled by a key which is kept secret between the communicants. 

- The purpose of this key lies in decryption of the cipher text. 

- Earlier the encryption and the decryption process were carried out directly by the ciphers without involvement of any integrity or authentication checks. 

- Before the advent of the modern cryptography, the traditional cryptography was known to be concerned only with the message confidentiality i.e., converting the message from comprehensible text in to incomprehensible text and vice versa. 

- The message was thus unreadable for the eavesdroppers and the interceptors without key. 

- For ensuring the secrecy in the communications, the encryption process was used. 

- But now the field expands far beyond the confidentiality issues.

- It now consists of techniques for authentication and message integrity checking, secure computation techniques, interactive proofs, digital signatures and so on. 

- Earlier two types of classical ciphers were used namely substitution ciphers and the transposition ciphers. 

- The former type involved replacing the letters by some other letters.

- The transposition ciphers involved rearrangement of the letters. 

- Some examples of early ciphers are caeser cipher, atbash cipher etc. 

- The early ciphers were assisted by some other physical aids and devices. 

- Eventually more complex ciphers could be developed with the development of the digital computers. 

- Any kind of data that could be represented in binary format could be encrypted.

How can firewalls secure a network?

Firewalls in computer systems are either software based or hardware based. But they have the same purpose of keeping a control over the incoming as well as the outgoing traffic. 

In this article we discuss about how the network is secured by the firewalls. 

- This control is maintained through the analyzation of the data packets. 

- After analyzation, the firewall’s work is to determine whether to allow these packets to pass or not. 

- This decision is taken based up on some set of rules.

- With this set of rules, a barrier is established by the firewall between the external network that is not considered as secure and trusted and the internal network which is secure and trusted. 

- Most of the personal computer’s operating systems come with a built-in software based firewall for providing protection against the threats from external networks. 

- Some firewall components might also be installed in the intermediate routers in the network. 

- Also some firewalls have been designed to perform routing as well.

There are different types of firewalls which function differently.This classification of the firewalls is based up on the place where the communication is taking place i.e., whether at the network layer or the application layer.

Packet filters or network layer: 

- Firewalls used at the network layer are often termed as the packet filters. 

- This firewall operates at low level of the protocol stack of the TCP/ IP and so does not allow the packets to pass through it unless they satisfy all the rules. 

- These rules might be defined by the administrator of the firewall. 

- These firewalls can also be classified in to two categories namely the stateless firewalls and the state-ful firewall. 

- The former kind use less memory and operates faster in the simple filters, thus taking less time for filtering. 

- These firewalls are used for filtering the stateless network protocols i.e., the protocols which do not follow the session concept. 

- These firewalls are not capable of making complex decisions based up on the state of the communication. 

- The latter kind maintains the context of the active sessions. 

- This state info is used by these firewalls for speeding up the packet processing. 

- A connection is described using any of the properties such as the UDP or TCP ports, IP addresses and so on. 

- If a match is found between an existing connection and the packet, it is allowed to pass. 

- Today firewalls have capabilities of filtering the packets based up on attributes like IP addresses of source and destination hosts, protocols, originator’s netblock, TTL values and so on.

Application layer Firewalls: 

- Firewalls of this type work on the TCP/ IP stack’s application level. 

- All the packets traveling in and out of the application are intercepted by this firewall. 

- This leads to blocking of the other packets also. 

- Firstly, all the packets are inspected for any malicious content for preventing the outspread of the Trojans and worms. 

- Some additional inspection criteria might be used for adding some extra latency to the packet forwarding. 

- This firewall determines whether a given connection should be accepted by a process. 

- This function is established by the firewalls by hooking themselves in to the socket calls for filtering the connections. 

- These application layer firewalls are then termed as the socket filters.

- There way of working is somewhat similar to the packet filters except that the rules are applied to every process rather than connections. 

- Also, the rules are defined using the prompts for those processes that have not been provided with a connection. 

- These firewalls are implemented in combination with the packet filters.

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 is fragmentation?

- The fragmentation technique is implemented in the IP (internet protocol) for breaking down the datagrams into smaller pieces. 

- This is done so that it becomes easy for the data packets to be passed through the link with a datagram size smaller than that of the original MTU or the maximum transmission unit. 

- The procedure for the IP fragmentation along with the procedures for reassembling and transmitting the datagrams is given in the RFC 791. 

- For determining the optimal MTU path, the IPv6 hosts are needed so that the packets can be sent. 

- If in case the PDU i.e., the protocol data unit received by the router is larger than the MTU of the next hop, then there are two options are available if IPv4 transport is being used:

Ø Dropping the PDU and sending an ICMP (internet control message protocol) message indicating that the condition packet is quite big.

Ø  Fragmenting the IP packet and then transmitting it over the link whose MTU is smaller. Any IPv6 packet with a size less than or equal to 1280 bytes can be delivered without having the need for using the IPv6 fragmentation.

- If a fragmented IP packet is received by the recipient host, its job is to reassemble the datagram and then send it over to the protocols at the higher layers. 

- The purpose of reassembling is expected to take place at the recipient’s host side but for some practical reasons it might be done by some intermediate router. 

- For example, the fragments might be reassembled by the NAT (network address translation) for translating the data streams. 

- Excessive re-transmission can result as a consequence of the IP fragmentation whenever packet loss might be encountered by the fragments. 

- It is required for all the reliable protocols (example, TCP) for re-transmitting the fragments in their correct order for recovering from the single fragment loss. 

Thus, typically two approaches are used by the senders for determining datagrams of what size should be transmitted over the network:

1. First approach: The sender must transmit an IP datagram of size as same as that of the first hop’s MTU.
2. Second approach: Running the path MTU discovery algorithm.

- Fragmentation does leave an impact on the network forwarding. 

- When there are multiple parallel paths for the internet router the traffic is split by the technologies such as the CEF and LAG throughout the links via some hash algorithms. 

- The major goal of this algorithm is to make sure that all the packets with the same flow are transmitted out on the same path for the minimization of the not so required packet reordering. 

- If the TCP or UDP port numbers are used by the hash algorithm, the fragmented packets might be forwarded through different paths. 

- This is so because the layer 4 information is contained only in the first fragment of the packet. 

- As a result of this, usually the initial fragment arrives after the non-initial fragments. 

- This condition is often treated as an error by most of the security devices in the hosts.  

- Therefore, they drop these packets.

- The fragmentation mechanism differs in IPv4 and IPv6. 

- In the former, the fragmentation is performed by the router. 

- On the other hand, in IPv6 fragments that are larger than MTU are dropped by the routers.

- Also, in both the cases there is a variation in the header format. 

- Since fragmentation is carried out using analogous fields, therefore the algorithm can be used again and again for the purpose of fragmentation and reassembling. 

- A best effort should be made by the IPv4 hosts for reassembling the datagram fragments. 

What are the differences between inter-network routing and intra-network routing?

- The individual networks when combined together form the inter-network. 

- Intermediate inter networking devices are used for making connections between them. 

- All these networking elements combine to work as single large unit. 

- The creation of the internetworking has been made possible because of the packet switching technology. 

- The router is the most common and important device used for performing inter-network routing and intranetwork routing.

- Routing across various networks in the inter network is termed as internetwork routing and routing within the same network is termed intranetwork routing. 

In this article we discuss about the differences between internetwork routing and intranetwork routing. 

- Just like inter-network, intranetwork also uses IP (internet protocol) technology for computing services and sharing information. 

- But what makes it different from internetworking is that it is limited to some organization whereas internetwork extends beyond all i.e., it is not limited.

- Or we can put it in other words: Internetwork is spread across organizations and Intranetwork lies within an organization. 

- In some cases, the term intranetwork might mean only the internal website of the organization, but in other cases it might be a larger part of the IT infrastructure of the organization. 

- Sometimes, it may span over a number of LANs (local area networks). 

- The intranetwork is driven by the goal of minimizing the time, effort and cost of the individual’s desktop in order to make it more competitive, cost efficient, timely as well as productive.

- An intranetwork is capable of hosting multiple websites that are private to organizations and may even constitute an important part of the collaboration and communication between the members of the organization. 

- Intranetwork also makes use of various well known protocols such as the FTP, SMTP and HTTP. 

- The intranets are often incorporated with the technologies for lending a modern interface to the systems that host the corporate data. 

- These systems are known as the legacy systems. 

- We can see intranetwork to be a private analog of the internetwork. 

- It means the internetwork has been simply extended to an organization for its private use. 

- Extranetworks are a modified version of the intranetworks.

- Here, the website might be accessed by the non-members i.e., the suppliers, customers or some other approved third parties and so on. 

- Intranetworks are well equipped with a special protocol called the AAA protocol. 

- The 3 As stand for authentication, authorization and accounting. 

- There are a number of organizations who are concerned about the security of their intranetworks. 

- They have deployed a firewall and a network gateway for controlling the access to their services. 

- The intermediate systems when connect together form the internetwork whereas they may bound together a part of the internetwork which might be an intranetwork. 

- The intranetwork routing involves routing between two routers which lie in the same network whereas in internetwork routing, routing is done between routers which reside across different networks. 

- Intranetwork routing is quite easy when compared to the internetwork routing. 

- Protocols used in both the types of routing are different.

- Interior gateway protocol is responsible for routing in the intranetworks whereas the exterior gateway protocol takes the responsibility of routing across the internetwork. 

- Most common example of interior gateway protocol is the OSPF or the open shortest path first protocol. 

- And most common example of exterior gateway protocol is the border gateway protocol or BGP. 

- Also, the routing graphs for both the types are different. 

- In the intranetwork’s graph, all the routers are simply linked to one another in the same network. 

- There is less mess.

- On the other hand, the inter network’s graph is quite tedious. 

- This is so because routers of different networks have to be inter-linked with one another.