Excel: A powerful tool for analysis (Simple operations)

Excel is a Microsoft product. It is very essential for data analysis. By using Excel, we can do thousands of things. But, we need to know the very basics so that we get going. First, we need to learn addition, subtraction, multiplication and division.  Then we need to go upwards by using power function and other complex math function. Actually, it reduces the task of a person. It reduces human error. Once you have made an excel sheet for analysis or doing a problem, you can get the results simply by changing the data. That is very easy. I will show you this in a video. Go through it and learn it. 

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What is the difference between a routing table and a forwarding table?

Routing tables are generally not used directly for packet forwarding in modern router architectures; instead, they are used to generate the information for a smaller forwarding table. A forwarding table contains only the routes which are chosen by the routing algorithm as preferred routes for packet forwarding. It is often in a compressed or pre-compiled format that is optimized for hardware storage and lookup.

Which major internet company or organization implements content centric networking?

NDN (one instance of CCN) has research collaborations with Cisco, Qualcomm, Comcast, Verisign, and Panasonic. In addition, Intel, Huawei, Alcatel-Lucent, and Orange all have significant projects exploring NDN-related ideas.
https://named-data.net/consortium/

What's the main role of DSCP in QoS?

DSCP’ s Role in QoS:

DSCP is the six most significant bit of the DiffServ (DS) field. The DiffServ architecture defines this DS field to make per-hop behaviour (PHB) the decision about packet classification and traffic conditioning a function such as metering, marking, shaping and policing.

There are three ways we can use DSCP field

1. Classifier: Select a packet based on the contents of some portions of the packet header and apply PHB based on service characteristics defined by the DSCP value
2. Marker: Set the DSCP field based on the traffic profile
3. Metering: check compliance to traffic profile using either a shaper or dropper function.

Note:

DiffServ is a computer networking architecture that specifies a simple and scalable mechanism for classifying and managing network traffic and providing quality of service (QoS) on modern IP networks. DiffServ can, for example, be used to provide low-latency to critical network traffic such as voice or streaming media while providing simple best-effort service to non-critical services such as web traffic or file transfers. (Reference: Wiki)

Difference between Poisson distribution and exponential distribution?

Poisson distribution talks about the number of events occur in an interval of time.

Exponential distribution talks about the time taken between two events occurring.

Which topology is used for a large network?

You can use RocketFuel topologies for testing

What is Transport layer?

When we read books we found about transport layer like below

“A transport-layer provides for logical communication between the application

processes running on different hosts”

By host we mean, all the devices like laptops, smartphones, tablets,

TVs, gaming consoles, Webcams, automobiles, environmental sensing devices that are hooked up to the Internet.

By Application process, we mean different applications like Facebook, Hotstar, youtube, Whatsapp in our mobile etc.

By logical communication, we mean that from an application’s perspective, it is as if the hosts running the processes were directly connected; in reality, the hosts may be on opposite sides of the planet, connected via numerous routers and a wide range of link types.

So when we chat with friends using Whatsapp, we send messages to one another

without worrying about details of the physical infrastructure used to carry these messages.

What is difference between network layer and transport layer?

The main difference between the network layer and the transport layer:

“The transport-layer layer provides logical communication between application processes running on different hosts”

On the other hand, the network-layer provides logical communication between hosts”

The terminologies are explained below (if anyone has doubt) (Notes part).

The difference can be explained using an analogy.

Suppose there are two orphanages: Orphanage A and Orphanage B. Both in two different cities in a state. Suppose some kids of A are siblings of B (only girls stay in A and only boys stay in B). The kid loves to write to each other every week. Suppose, Alice is the caretaker of A and Bob is the caretaker of B. Both Alice and Bob are responsible for letter collection and distribution. Letters are sent inside an envelope using traditional postal service.

Each week Alice visits all the kids, collects the letters, and gives them to a postal-service mail carrier, who makes daily visits to the house. When letters arrive at A, Alice also has the job of distributing the letter to kids. Bill has a similar job on orphanage B.

application messages = letters in envelopes

processes = kids

hosts = houses

transport-layer protocol =Alice and bob

network-layer protocol = postal service (including mail carriers)

Note:

By host we mean, all the devices like laptops, smartphones, tablets,

TVs, gaming consoles, Webcams, automobiles, environmental sensing devices that are hooked up to the Internet.

By Application process, we mean different applications like Facebook, Hotstar, youtube, Whatsapp in our mobile etc.

By logical communication, we mean that from an application’s perspective, it is as if the hosts running the processes were directly connected; in reality, the hosts may be on opposite sides of the planet, connected via numerous routers and a wide range of link types.

So when we chat with friends using Whatsapp, we send messages to one another

without worrying about details of the physical infrastructure used to carry these messages.

What's the difference between packet transmission delay and propagation delay?

Difference between packet transmission delay and propagation delay:

Suppose there are two hosts H1 and H2. H1 and H2 are connected by a network or communication links (transmission media). H1 wants to send some packets (bits) to H2.

Now the time taken to place the complete data packets on the transmission media/link is called a transmission delay (Td).

If we want to put a large packet on the link, it will take more time. In addition to that if the link has more capacity/bandwidth, the time required will be less as compared to the link with less bandwidth.

So, obviously, this Td will depend on the length of the packet and bandwidth of the link.

Td= length of the data packet(l) / bandwidth of the network (BW)

So for example, if l=1000 bit and BW= 1K bits/sec,

then Td=1sec

So, we can understand that transmission delay just involves the time to place the packet in the network. But yet the data packet till not reached to H2.

Propagation delay (Tp): Time taken to transfer 1 bit from H1 to H2 is called Propagation delay.

Now, we can think if the distance between H1 and H2 is large, definitely the Tp will be more. Moreover, Tp will also depend on the speed of the signal (like the speed of a car).

Tp= distance (d)/ transmission speed (s)

So for example, if d=9km and s= 3 xX10 ^8 m/sec,

then Td =3 X 10 ^-5 sec

What are some ways in which congestion could affect network performance?

Congestion can affect the QoS and QoE of the users by

1. Increasing the response time of users. This is due to the increase in queuing delay at routers due to congestion. It will severely affect the delay-sensitive applications.
2. Throughput may decrease due to dropping of packets due to buffer overflow.

What is QOS in networking?

We all use different apps like YouTube, Hotstar, Netflix on our mobile phone. These applications use multimedia streaming of data. The nature of streaming data is much different from the nature of normal file transfer. Now a simple thought may come to your mind: What is the difference?

In the case of file transfer, we just need to transfer the bytes from one end to the other end, and whenever we receive all the bytes in the other end, we just combine all the bytes together and reconstruct the file.

On the other hand, in case of multimedia streaming e.g. YouTube streaming (when we watch a YouTube video online) data comes over the Internet and we are playing it simultaneously. While playing the video on YouTube, the video data is getting transmitted continuously from the YouTube server to the client which is running at our browser. You can notice that many a time video got stuck and circular things are rounding (which we call re-buffering).

So for this kind of video transmission, we need to maintain a certain level of Quality of Service(QoS). Qos in the sense that what the other end or the client-side is expecting from the Internet. So, in the case of YouTube video streaming, the youTube client is expecting a continuous stream of videos such that it can render the video directly on the player and play the video without this kind of quality drop or re-buffering. So that is why, to ensure such kind of application quality, we need to provide certain special services at the Internet level.

So, I think now we can clearly understand the definition (from Book):

QoS is the ability of the network to provide better or special service to a set of users and application to the detriment of others.

• “the the ability of the network”-it means that this will be done by network infrastructure i.e., switches and routers. There will be no traffic shaping server, the network infrastructure has to do this job.
• “to provide better or ‘special’ service”,- it means some traffic flow will be given preferential treatment and others will be given what is left over.
• “To a set of users and applications”, -it means which flow should get preference and which will get detriment treatment or less BW
• “To the detriment of others”-it means that since there will be a finite amount of bandwidth if some flow is given more bandwidth there will be less available for the remaining traffic.

Note: Don’t confuse with the offline video downloading which is different from Youtube Streaming. Offline video downloading is just similar to normal file transfer. It is just transferring the video file and playing it offline.

What is Layer 2?

Layer2 is Data link layer.

Difference between etwork driver and Network adapter

The simplest difference between Network driver and Network adapter: Network driver is software and Network adapter is hardware.

Note: Network adapter (also called NIC (network interface card) ) is a computer hardware component that connects a computer to a computer network. NIC will not work without a software driver to control the hardware.

Which network was designed by the United States Defence Department to share data?

ARPANET

What is the difference between throughput and goodput?

 I found the link below which clearly describes the difference between throughput and goodput.
 
https://packetpushers.net/throughput-vs-goodput/

What basic functions does the IPv4 header checksum field perform?

H1————R1————R2————H2

Suppose you want to send a packet from host H1 to host H2. The packet may get corrupted due to various reasons like interference, fading etc. In that case, IPv4 header checksum helps us to find out whether the packet has been received correctly received or not. Note that the checking is done only at the header part, not on the data part. The reason is that data checking is already done at the transport layer. Another point is that we are not correcting it we are just identifying it. To find the checksum we use 1’s complement method.

Please visit my blog for knowing more information on network

What is IP cloaking?

IP cloaking is the process of a web server delivering a specific web page based on the visitors IP address.

Suppose, you are visiting a website The Network Forum from France, the contents are in French language, whereas, if you are searching from India, the information appears to be in Hindi. Web server checks the IP address of your device and give different versions.

Which topology uses a centralized device for connectivity?

Star topology

What are the difference between forwarding and routing?

In the simplest way:

Forwarding: Looking up for destination in the routing table.

Routing: construction of routing table (Algorithms or protocols that are used to build the routing table) at each switch/router in the network.

 If you have query write in the comment section.

How is it possible to use the AES encryption algorithm for an IBE (identity-based encryption) scheme?

It is possible to use AES encryption algorithm for an IBE (identity-based encryption) scheme.

Both are completely different. AES is an asymmetric encryption algorithm. Here the same key is used for both encryption and decryption.

On the other hand, IBE is a kind of asymmetric encryption. In asymmetric encryption, the message is encrypted with the public key and the receiver decrypts the message with the private key. But in general public keys are stored in public directory and public key certificates are needed to prove the authenticity of the public key. The management of public key directory and the public key certificate is complex.

So a new encryption scheme is proposed in which the public key is derived from the unique identity like Gmail of the user. So there will be no headache of certificate management.

If you have query write in the comment section. 

What data structures are more efficient than hash tables?

It is not possible to tell directly which data structure is more efficient than a hash table. It depends on the application. Every data structure has its own unique characteristics.

In some cases, bloom filter and trie works better than hash table.

Below I am just trying to give you an overview.

1. Longest prefix match in routing tables: In this case, the hash table will not be efficient. Here trie is better than hash table. Applications where the entries share common prefixes, it is better to implement with trie.
2. In case some applications where u just want to know where the content exists or not, then it is better to apply Bloom Filter, as it is very fast as compared to the hash table. It also consumes less memory. But the main drawback of the bloom filter is a false positive. It means when the answer is negative it is 100% correct but the in the other case sometimes it may be wrong.