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Ok so the busiest tollywood hero is  going to be married. Now this report is based on a interview taken by some reporter  and published in some  magagazine/newspaper.

Why he opt for settled marriage ?

As the actor said that he  always a liked the arranged marriage .Then he said that he left the responsibility to choose the right partner for him to his parents as he know that parents will always choose the best for    him.

 According to the ACTOR Jeet the arranged marriage just like an adventure where many good phases has to be revealed after the marriage.People will discover each other after they marry.

When asked about that what his to be bride think about his profession then he said that his to be bride have seen few of his movies and they also discussed about that and she also respect his profession as well as she can be a good critic of his films .According to the Jeet the career of family background of both the families are almost the same and certainly this will help in adjusting the going to be relation ship between the two families.

How did Jeet found out his life partner?

As the actor said there was a lady in lucknow who was his sisters relative, According to the actor that lady suggested   him to marry the to be bride of jeet.

Then after the actor meets her, he begins to like her    and amazed to her simplicity and found that she can be fitted as his life partner.

When asked about that whether the actor thinks that his bride(to be) may come in film-then actor said that he don’t think so .

What is the date of the marriage:

As  the actor said it may be on February 2011.

Now  who is the  girl??

She is a lucknow based school teacher name Mohna.

We all welcome Mohna to WestBengal.

Perhaps the most important service provided by X.25 is multiplexing. A DTE is allowed to establish up to 4095 simultaneous virtual circuits with other DTEs over a single DTE-DCE link. The DTE can internally assign these circuits in anyway it pleases. Individually virtual circuits could correspond to applications, process, or terminals for example. The DTE-DCE link provides full duplex multiplexing, i.e., at anytime, a packet associated with a given virtual circuit can be transmitted in either direction.

To sort out which packets belong to which virtual circuits, each packet contains a 12-bit virtual circuit number. The assignment of virtual circuit numbers follows the convention depicted in the figure. Number zero is always reserved for diagnostic packets common to all virtual circuits. Then contiguous ranges of numbers are allocated for four categories of virtual circuits. Permanent virtual circuits are assigned numbers beginning with 1. The next category is one way, incoming virtual calla. This means that only incoming calls from the network can be assigned these numbers; the virtual circuit however, is two-way (full duplex). When a call request comes in, the DCE selects an unused number from this category.

One-way outgoing calls are those initiated by the DTE. In this case, the DTE selects an unused number from among those allocated for these calls. This separation of categories is intended to avoid the simultaneous selection of the same number for two different virtual circuits by the DTE and DCE.

The two-way virtual-call category provides an overflow for allocation shared by DTE and DCE, allowing for peak differences in traffic flow.

One interesting comparison can be made between these two algorithms. Consider first the Bellman-Ford algorithm where the calculation for node n involves knowledge of the link cost to all neighboring nodes to node n ( djn) plus the total path cost to each of those neighboring nodes from a particular source node s. Each node can maintain a set of costs and associated paths for every other node in the network and can exchange this information with its direct neighbors from time to time. Each node therefore deals with only one information from its neighbors and knowledge of its link costs,to update its costs and paths. On the other hand in  Dijkstra’s algorithm each node must have complete topological information about the network. That is each node must know the link costs of all links in the network. Thus  for this algorithm, information must be exchanged with all other nodes.
A final point : Both algorithms are known to converge under static conditions of topology and link costs and will converge to the same solution. If the link cost change over time, the algorithm will attempt to catch up with these changes. However , if the link cost depends on traffic ,which in turn depends on the routes chosen, then a feedback condition exists, and instabilities may result.

What is ASN.1? Write down the utilities for using ASN.1.

Ans. ASN.1 is the acronym of Abstract Syntax Notation One. The development of ASN.1 is the most significant development in computer communications. It has become an important universal language for defining application-level protocols. ASN.1 is a language that can be used to define data structures. A structure definition is in the form of a named module.The named module can then be used to reference the structure.

The Abstract Syntax is used for the exchange consists of application-level PDUs,which contain protocol control information and user data.within a system, the information represented using an Abstract Syntax must be mapped into some form for presentation to the human user.Thus the Abstract Syntax Notation is employed by a user to define network management information; the application must then convert this definition to a form suitable for local storage.

What is X.25 interface? Define DTE & DCE

The X.25 software and hardware allow the router to communicate over a public X.25 network. The X.25 network interface complies with CCITT 1980 and 1984 specifications for X.25 interfaces by offering multiplexed channels and reliable end-to-end data transfer across a WAN. Layer 1 X.25 defines the electrical and mechanical procedures for activating and deactivating the physical medium connecting the DTE and the DCE. This relationship is shown below:

DTE: DTE or Data terminal equipment devices are end systems that communicate across the X.25 network. They are usually terminals, personal computers, or network hosts, and are located on the premises of individual subscribers.

DCE: DCE or Data circuit-terminating equipment are communications devices, such as modems and packet switches that provide the interface between DTE devices and a PSE (Packet-switching exchange), and are generally located in the carrier’s facilities.

Briefly describe multiplexing service of X.25. How flow control & error control is being achieved in X.25

Multiplexing of virtual circuits takes place at layer 3.The traditional approach to packet switching makes use of X.25, which not only determine the user network interface but also influences the internal design of the network. Today’s networks employ reliable digital transmission technology over high quality, reliable transmission links, many of which are optical fiber. Thus multiplexing of X.25 makes its more reliable & easily operable.

Flow control is generally based on the start & waits technique and is achieved by using an acknowledgement (ACK) for error free frames & a negative acknowledgement (Nak) for frames containing error. Ack0 & Ack1 are usually used alternately for detecting sequence errors, which are caused by either, duplicated or lost frames.

Error control is achieved by 16-bit CRC or FCS algorithm. In the event of an error frame, the sender retransmits the frame to the receiver.

For fixed routing, a single, permanent route is configured for each source- destination pair of nodes in the network. It determines routes using a least cost algorithm. The routes are fixed, or at least only change when there is a change in the topology of the network. A central routing matrix is created for implementing fixed routing which is shown below:

: First Generation adaptive algorithm

In this algorithm, each node maintains two vectors:

Where

Di = delay vector for node i

dij = current estimate of minimum delay from node i to node j (dij = 0)

N = number of nodes in network

Si = successor node vector for node i

sij = the next node in the current minimum delay route from i to j

Periodically each node exchanges its delay vector with all of its neighbors. On the basis of all incoming delay vectors, a node k updates both of its vectors as follows:

Delay for going k to j node, dkj = min [d _ij + l _ki ]

i € A

s _kj = i using i that minimizes the preceding expression

where

A = set of neighbor nodes for k

l _ki = current estimate of delay from k to i

Figure below provides an example of the original ARPANET algorithm:

• For network above, snapshot for node 1 shown

• Later, link costs change in the network

• Update comes in from its neighbors (2, 3, 4)

LAPB (Link Access Protocol Balanced) is a data link layer protocol that manages communication and packet framing between DTE and DCE devices. LAPB is a bit-oriented protocol that ensures that frames are correctly ordered and error-free.

LAPB uses three frame format types:

Information (I) frame- These frames carry upper-layer information and some control information (necessary for full-duplex operation). I-frame functions include sequencing, flow control, and error detection and recovery. I-frames carry send- and receive-sequence numbers.

Supervisory (S) frames- These frames provide control information. They request and suspend transmission, report on status, and acknowledge the receipt of I frames. They do not have an information field.

Unnumbered (U) frames- These frames are not sequenced. They are used for control purposes. For example, they can initiate a connection using standard or extended windowing (modulo 8 versus 128), disconnect the link, report a protocol error, or similar functions.

Ø Flag- Delimits the LAPB frame. Bit stuffing is used to ensure that the flag pattern does not occur within the body of the frame.

Ø Address- Indicates whether the frame carries a command or a response.

Ø Control- Provides further qualifications of command and response frames, and also indicates the frame format (U, I, or S), frame function (for example, receiver ready or disconnect), and the send/receive sequence number.

Ø Data- Carries upper-layer data. Its size and format vary depending on the Layer 3 packet type. The maximum length of this field is set by agreement between a PSN administrator and the subscriber at subscription time.

Ø Frame check sequence (FCS)- Ensures the integrity of the transmitted data.

What are the differences between datagram approach virtual circuit approaches in packet switching network? Which one is advantageous & why?

The datagram service, coupled with internal datagram operation, allows for efficient use of the network; no call setup and no need to hold up packets while a packet in error is retransmitted. This latter feature is desired in some real-time applications.

The virtual-circuit service can provide end-to-end sequencing and error control; this service is attractive for supporting connection-oriented applications, such as file transfer and remote-terminal access.

In practice, the virtual-circuit service is much more common than the datagram service. The reliability and convenience of a connection-oriented service is seen as more attractive than the benefits of the datagram services

What is HDLC?

HDLC (High-Level Data Link Control) is a bit-oriented synchronous data link layer protocol developed by the International Organization for Standardization (ISO). It provides both connection oriented & connectionless service. HDLC can be used for point to multipoint connections, but is now used almost exclusively to connect one device to another, using what is known as Asynchronous Balanced Mode (ABM).

Describe supervisory frame in HDLC

Supervisory Frames (S-frames) in HDLC are used for flow and error control whenever piggybacking is impossible or inappropriate, such as when a station does not have data to send. S-frames do not have information fields.

The S-frame control field includes a leading “10″ indicating that it is an S-frame. This is followed by a 2-bit type, a poll/final bit, and a sequence number. If 7-bit sequence numbers are used, there is also a 4-bit padding field. The first 2 bits mean it is an S-frame. Poll/Final bit is called Poll when used by the primary station to obtain a response from a secondary station, and Final when used by the secondary station to indicate a response or the end of transmission.

Write the sequences for HDLC initialization

Ans: Initialization may be requested by either side by issuing one of the six set-mode commands. This command serves three purposes:

It signals the other side that initialization is requested

It specifies which of the three modes ( NRM, ABM, ARM ) is requested.

It specifies whether 3- or 7-bit sequences numbers are to be used.

If the other side accepts this request, then the HDLC module on that end transmits an unnumbered acknowledged (UA) frame back to the initiating side. If the request is rejected, then a disconnected mode (DM) frame is sent.

HDLC is the protocol which is now considered an umbrella under which many Wide Area protocols sit. ITU-T developed HDLC in 1979, and within HDLC there are three types of stations defined:

• Primary Station - this completely controls all data link operations issuing commands from secondary stations and has the ability to hold separate sessions with different stations.
• Secondary Station - this can only send responses to one primary station. Secondary stations only talk to each other via a Primary station.
• Combined Station - this can transmit and receive commands and responses from one other station.

When transferring data, stations are in one of three modes:

• Normal Response Mode (NRM) where the secondary station needs permission from the primary station before it can transmit data. Mainly used on multi-point lines.
• Asynchronous Response Mode (ARM) where the secondary station can send data without receiving permission from the primary station. This is hardly ever used.
• Asynchronous Balanced Mode (ABM) where either station can initiate transmission without permission from the other. This is the most common mode used on point-to-point links.

There are three types of HDLC frame types defined by the control field:

• Information Frames are used for the data transfer between stations. The send sequence, or next send N(S), and the receive sequence, or next receive N(R), hold the frame sequence numbers. The Poll/Final bit is called Poll when used by the primary station to obtain a response from a secondary station, and Final when used by the secondary station to indicate a response or the end of transmission.
• Supervisory Frames are used to acknowledge frames, request for retransmissions or to ask for suspension of transmission. The Supervisory code denotes the type of supervisory frame being sent.
• Unnumbered Frames are used for link initialisation or link disconnection. The Unnumbered bits indicate the type of Unnumbered frame being used.

The project idea is to create a system to prevent the trains from colliding with each other i.e to prevent the accident of trains. Now for simple  idea of projects :
Each train has some IR(very intense and highly collimated beam) transmitter as well as receiver at the front and at the back of trains .Now total  the system consists of IR Transceiver and Microcontroller. Now each train has some unique ID (Train Number) that is there inside the microcontroller ROM. Now When two trains will come nearly face to face  i mean consider the situation when two trains coming head on –on  a single line, now when ever they are at a distance between the range of IR transmitters then both train will  receive a transmitted signal form each other  microcontroller will give proper signal so that the  actuator/relay may be able to stop the trains before they collide.
But for this situation to occur following important things need to be considered and tested accordingly.
What are the ranges of the train’s IR transceivers ? Is that range is sufficient to stop the trains at that distance before they collide. As each train will take some distance or move a considerable amount of distance after is breaks are pressed or activated and trying to stop .Also at what velocity the trains are approaching to each other: So those  information are required to know, what IR range and transceivers we are going to choose .for example if the trains for which this system is going to be implemented the maximum possible speed say 200 Km/Hr, and say when the  trains are running at their maximum speed, then it need to be tested that within  how much distance the trains will be stopped after it the breaks are pressed.
Now another things are needed to be considered -are the tracks are linear because the IR sensor etc will work only for linear tracks( i.e. straight line).
So these things are to be taken care off when doing or creating the design according to this methodology.

NOW part 2 will have another approach for anti-collision system design.

See More here …