1.List out the features of x.25 ROEVER ENGINEERING COLLEGE Elambalur,Perambalur-621212 DEPARTMENT OF CSE NP UNIT-I * Call control packets, used for setting up and clearing virtual circuits, are carried on the same channel and the same virtual circuit as data packets. In effect, inband signaling is used. * Multiplexing of virtual circuits takes place at layer 3. * Both layer 2 and layer 3 include flow control and error control mechanisms 2.what are the key difference between frame rely and x.25? * Call control signaling is carried on a separate logical connection from user data. Thus, intermediate nodes need not maintain state tables or process messages Relating to call control on an individual per-connection basis. * Multiplexing and switching of logical connections take place at layer 2 instead Of layer 3, eliminating one entire layer of processing. * There is no hop-by-hop flow control and error control. End-to-end flow control
And error control, if they are employed at all, are the responsibility of a higher layer. 3. Explain about the frame rely architecture. Frame rely architecture support two modes of operation that is two separate planes of operation: a control (C) plane, which is involved in the establishment and termination of logical connections, and a user (U) plane, which is responsible for the transfer of user data between subscribers. Thus, C-plane protocols are between a subscriber and the network, while U-plane protocols provide endto-end functionality 4. What are the core functions of LAPF? * Frame delimiting, alignment, and transparency * Frame multiplexing/demultiplexing using the address field * Inspection of the frame to ensure that it consists of an integral number of octets prior to zero-bit insertion or following zero-bit extraction * Inspection of the frame to ensure that it is neither too long nor too short * Detection of transmission errors * Congestion control functions *The last function listed above is new to LAPF
5. What is control plan? The control plane for frame-mode bearer services is similar to that for common channel Signaling in circuit-switching services, in that a separate logical channel used for control information. In the case of ISDN, control signaling is done over the D channel, to control the establishment and termination of frame-mode virtual calls on the D, B, and H channels (see Appendix A). At the data link layer, LAPD (Q.921) is used to provide a reliable data link control service, with error control and flow control, between user (TE) and network (NT) over the D channel. This data link service is used for the exchange of Q.933 control-signaling messages. 6. W hat is user plan? For the actual transfer of information between end users, the user-plane protocol is LAPF (Link Access Procedure for Frame-Mode Bearer Services), which is defined in Q.922. Q.922 is an enhanced version of LAPD (Q.921). Only the core functions of LAPF are used for frame relay: * Frame delimiting, alignment, and transparency * Frame multiplexing/demultiplexing using the address field * Inspection of the frame to ensure that it consists of an integral number of octets prior to zero-bit insertion or following zero-bit extraction * Inspection of the frame to ensure that it is neither too long nor too short * Detection of transmission errors * Congestion control functions
7. Give the various view point of ISDN? * Principles of ISDN * The user interface * Objectives * Services 8. List out the services of ISDN? 1. Support of voice and nonvoice applications using a limited set of Standardized Facilities 2. Support,for switched and nonswitched applications 3. Reliance on 64-kbps connections. 4. Intelligence in the network. 5. Layered protocol architecture. 9. List out the objectives of ISDN? Standardization Transparency. Separation of competitive functions.
eased and switched services. Cost-related tariffs.. Smooth migration. Multiplexed support. 10. List out the series of ISDN. * 1.100 Series-General Concepts * 1.200 Series-Service Capabilities * 1.300 Series-Network Aspects * 1.400 Series-User-Network Interfaces * 1.500 Series-Internet work Interfaces * 1.600 Series-Maintenance Principles 11. Give the types of ISDN channel. * B channel: 64 kbps * D channel: 16 or 64 kbps * H channel: 384(H0), 1536(H11), and 1920 (H12) kbps
12. What is B channel? The B channel is the basic user channel. It can be used to carry digital data, PCM-encoded digital voice, or a mixture of lower-rate traffic, including digital data and digitized voice encoded at a fraction of 64 kbps. In the case of mixed traffic, all traffic must be destined for the same endpoint. 13. How do you set up connection over B channel? * Circuit-switched. * Packet-switched. * Frame mode. * Semipermanent. 14. What is D channel? The D channel serves two purposes. First, it carries signaling information to control circuitswitched calls on associated B channels at the user interface. In addition, the D channel may be used for packet-switching or low-speed (e.g., 100 bps) telemetry at times when no signaling information is waiting. 15. What is H channel? H channels are provided for user information at higher bit rates. The user may employ such a channel as a high-speed trunk, or the channel may be subdivided according to the user's own TDM scheme.
Examples of applications include fast facsimile, video, high-speed data, high-quality audio, and multiple information streams at lower data rates. 16. How do you establish ISDN connection? ISDN provides four types of service for end-to-end communication: * Circuit-switched calls over a B channel. * Semi permanent connections over a B channel. * Packet-switched calls over a B channel. * Packet-switched calls over the D channel. UNIT-II 1.List out the features of x.25 * Call control packets, used for setting up and clearing virtual circuits, are carried on the same channel and the same virtual circuit as data packets. In effect, inband signaling is used. *Multiplexing of virtual circuits takes place at layer 3. *Both layer 2 and layer 3 include flow control and error control mechanisms 2.what are the key difference between frame rely and x.25? * Call control signaling is carried on a separate logical connection from user data.
Thus, intermediate nodes need not maintain state tables or process messages Relating to call control on an individual per-connection basis. * Multiplexing and switching of logical connections take place at layer 2 instead Of layer 3, eliminating one entire layer of processing. * There is no hop-by-hop flow control and error control. End-to-end flow control And error control, if they are employed at all, are the responsibility of a higher layer. 3. Explain about the frame rely architecture. Frame rely architecture support two modes of operation that is two separate planes of operation: a control (C) plane, which is involved in the establishment and termination of logical connections, and a user (U) plane, which is responsible for the transfer of user data between subscribers. Thus, C-plane protocols are between a subscriber and the network, while U-plane protocols provide endto-end functionality 4. What are the core functions of LAPF? * Frame delimiting, alignment, and transparency * Frame multiplexing/demultiplexing using the address field * Inspection of the frame to ensure that it consists of an integral number of octets prior to zero-bit insertion or following zero-bit extraction * Inspection of the frame to ensure that it is neither too long nor too short
* Detection of transmission errors * Congestion control functions *The last function listed above is new to LAPF, and 5. What is control plan? The control plane for frame-mode bearer services is similar to that for common channel Signaling in circuit-switching services, in that a separate logical channel used for control information. In the case of ISDN, control signaling is done over the D channel, to control the establishment and termination of framemode virtual calls on the D, B, and H channels (see Appendix A). At the data link layer, LAPD (Q.921) is used to provide a reliable data link control service, with error control and flow control, between user (TE) and network (NT) over the D channel. This data link service is used for the exchange of Q.933 control-signaling messages. 6. W hat is user plan? For the actual transfer of information between end users, the user-plane protocol is LAPF (Link Access Procedure for Frame-Mode Bearer Services), which is defined in Q.922. Q.922 is an enhanced version of LAPD (Q.921). Only the core functions of LAPF are used for frame relay: * Frame delimiting, alignment, and transparency
* Frame multiplexing/demultiplexing using the address field * Inspection of the frame to ensure that it consists of an integral number of octets prior to zero-bit insertion or following zero-bit extraction * Inspection of the frame to ensure that it is neither too long nor too short * Detection of transmission errors * Congestion control functions 7. Give the various view point of ISDN? * Principles of ISDN * The user interface * Objectives * Services 8. List out the services of ISDN? 1. Support of voice and nonvoice applications using a limited set of Standardized Facilities 2. Support,for switched and nonswitched applications
3. Reliance on 64-kbps connections. 4. Intelligence in the network. 5. Layered protocol architecture. 9. List out the objectives of ISDN? Standardization Transparency. Separation of competitive functions. eased and switched services. Cost-related tariffs.. Smooth migration. Multiplexed support. 10. List out the series of ISDN. * 1.100 Series-General Concepts * 1.200 Series-Service Capabilities * 1.300 Series-Network Aspects
* 1.400 Series-User-Network Interfaces * 1.500 Series-Internet work Interfaces 1.600 Series-Maintenance Principles 11. Give the types of ISDN channel. * B channel: 64 kbps * D channel: 16 or 64 kbps * H channel: 384(H0), 1536(H11), and 1920 (H12) kbps 12. What is B channel? The B channel is the basic user channel. It can be used to carry digital data, PCM-encoded digital voice, or a mixture of lower-rate traffic, including digital data and digitized voice encoded at a fraction of 64 kbps. In the case of mixed traffic, all traffic must be destined for the same endpoint. 13. How do you set up connection over B channel? * Circuit-switched. * Packet-switched. * Frame mode.
* Semipermanent. 14. What is D channel? The D channel serves two purposes. First, it carries signaling information to control circuit-switched calls on associated B channels at the user interface. In addition, the D channel may be used for packet-switching or low-speed (e.g., 100 bps) telemetry at times when no signaling information is waiting. 15. What is H channel? H channels are provided for user information at higher bit rates. The user may employ such a channel as a high-speed trunk, or the channel may be subdivided according to the user's own TDM scheme. Examples of applications include fast facsimile, video, high-speed data, highquality audio, and multiple information streams at lower data rates. 16. How do you establish ISDN connection? ISDN provides four types of service for end-to-end communication: * Circuit-switched calls over a B channel. * Semipermanent connections over a B channel. * Packet-switched calls over a B channel. * Packet-switched calls over the D channel.
UNIT-III 1. What are the essential ingredients of a symmetric cipher? It consists of five ingredients namely Plain text Encryption algorithm Secret key Cipher key Decryption algorithm 2. What are the two basic functions used in encryption algorithms? The two basic functions used in encryption algorithms are Substitution Transposition 3. How many keys are required for two people to communicate via a cipher? If both sender and receiver use the same key, the system is referred to as symmetric, single key, or conventional encryption. If the sender and receiver each use a different key, the system is referred to as asymmetric two-key, or public-key encryption 4. What is the difference between a block cipher and a stream cipher? A block cipher processes the input one block of elements at a time, producing an output block for each input block. A stream cipher processes the input elements continuously, producing output one element at a time, as it goes along.
5. What are the essential ingredients of a symmetric cipher? It consists of five ingredients namely Plain text Encryption algorithm Secret key Cipher key Decryption algorithm 6. how do you encryption and decryption are done using RSA crypto-system. RSA cryptosystem: 1. Generate two large random primes, p and q, of approximately equal size such that their product n=p q is of the required bit length. 2. Compute n=pq and and (o) phi=(p-1)(q-1). 3. Choose an integer e,1<e<phi, such that gcd(e,phi)=1. 4. Compute the secret exponent d,1<d<phi, such that ed=1 (mode phi). 5. The public key is(n,e) and the private key is (n,d). Keep all the values d,p,q and phi secret. 7.How do elliptic curve take part in encryption and decryption process? Encryption: Sender A does the following: 1. Obtain the recipint B s public key (n,e) 2. Represents the plaintext message a positive integer m. 3. Computes the ciphertext c=m mod n 4. Sends the ciphertext c to B 8. What is message authentication? It is a procedure that verifies whether the received message comes from assigned source has not been altered. It uses message authentication codes, hash algorithms to authenticate the message.
9. Define the classes of message authentication function. Message encryption: The entire cipher text would be used for authentication. Message Authentication Code: It is a function of message and secret key produce a fixed length value. Hash function: Some function that map a message of any length to fixed length which serves as authentication. 10. What are the requirements for message authentication? The requirements for message authentication are Disclosure: Traffic Analysis: Masquerade: Content modification:. Sequence modification: Timing modification: Source repudiation: Destination repudiation: 11. What you meant by hash function? Hash function accept a variable size message M as input and produces a fixed size hash code H(M) called as message digest as output. It is the variation on the message authentication code. 12. Differentiate MAC and Hash function? MAC: In Message Authentication Code, the secret key shared by sender and receiver. The MAC is appended to the message at the source at a time which the message is assumed or known to be correct. Hash Function: The hash value is appended to the message at the source at time when the message is assumed or known to be correct. The hash function itself not considered to be secret. 13. Any three hash algorithm. MD5 (Message Digest version 5) algorithm.
SHA_1 (Secure Hash Algorithm). RIPEMD_160 algorithm. 14. What are the requirements of the hash function? H can be applied to a block of data of any size. H produces a fixed length output. H(x) is relatively easy to compute for any given x, making both hardware and software implementations practical. 15. What you meant by MAC? MAC is Message Authentication Code. It is a function of message and secret key which produce a fixed length value called as MAC. MAC = CK (M) Where M K = variable length message = secret key shared by sender and receiver. C K(M) = fixed length authenticator. 16. Differentiate internal and external error control. Internal error control: In internal error control, an error detecting code also known as frame check sequence or checksum. External error control: In external error control, error detecting codes are appended after encryption. 17. What is the meet in the middle attack? This is the cryptanalytic attack that attempts to find the value in each of the range and domain of the composition of two functions such that the forward mapping of one through the first function is the same as the inverse image of the other through the second function-quite literally meeting in the middle of the composed function. 18. What is the role of compression function in hash function? The hash algorithm involves repeated use of a compression function f, that takes two inputs and produce a n-bit output. At the start of hashing the chaining variable has an initial value that is specified as part of
the algorithm. The final value of the chaining variable is the hash value usually b>n; hence the term compression.