4.1 DESIGN ISSUES OF TRANSPORT LAYER 4.2 DESIGN ISSUES OF SESSION LAYER 4.3 DESIFN ISSUES OF PRESENTATION LAYER 4.5 TCP WINDOW MANAGEMENT

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1 UNIT DESIGN ISSUES OF TRANSPORT LAYER 4.2 DESIGN ISSUES OF SESSION LAYER 4.3 DESIFN ISSUES OF PRESENTATION LAYER 4.4 CONNECTION MANAGEMENT & THREE WAY HANDSHAKE 4.5 TCP WINDOW MANAGEMENT 4.6 REMOTE PROCEDURE CALL 4.7 DATA COMPRESSION TECHIQUES 4.8 CRYPTOGRAPHY 4.9 IEEE FORMAT FORMAT FORMAT FORMAT FORMAT 1 EDITED BY: PAWAN PANDEY

2 4.1 DESIGN ISSUES OF TRANSPORT LAYER: The various functions of transport layer are: a) Establishing, Maintaining & Releasing Connection b) Addressing c) Data Transfer d) Flow Control e) Error Control f) Congestion Control 4.2 DESIGN ISSUES OF SESSION LAYER: Authentication Authentication is the act of establishing or confirming something (or someone) as authentic, that is, that claims made by or about the thing are true. This might involve confirming the identity of a person, the origins of an artifact, or assuring that a computer program is a trusted one Permissions or Access control One familiar use of authentication and authorization is access control. A computer system supposed to be used only by those authorized must attempt to detect and exclude the unauthorized. Access to it is therefore usually controlled by insisting on an authentication procedure to establish with some established degree of confidence the identity of the user, thence granting those privileges as may be authorized to that identity Checkpoints Session layer is responsible for creating several checkpoints, checkpoints are also treated as recovery points i.e. in case of failure the system rollback to its previous checkpoint configuration or action. 4.3 DESIFN ISSUES OF PRESENTATION LAYER: a) Data encryption/decryption b) Character/string conversion c) Data compression d) Graphic handling 2 EDITED BY: PAWAN PANDEY

3 4.4 CONNECTION MANAGEMENT & THREE WAY HANDSHAKE : A TCP connection is defined to be a 4-tuple consisting of two IP addresses and two port numbers. It is a pair of endpoints or socketswhere each endpoint is identified by an (IP address, port number) pair. A connection typically goes through three phases: a) Setup b) Data transfer (called established) c) Teardown (closing). A three-way handshake is a method used in a TCP/IP network to create a connection between a local host/client and server. It is a three-step method that requires both the client and server to exchange SYN and ACK (acknowledgment) packets before actual data communication begins. A three-way handshake is also known as a TCP handshake. a) A client node sends a SYN data packet over an IP network to a server on the same or an external network. The objective of this packet is to ask/infer if the server is open for new connections. b) The target server must have open ports that can accept and initiate new connections. When the server receives the SYN packet from the client node, it responds and returns a confirmation receipt the ACK packet or SYN/ACK packet. c) The client node receives the SYN/ACK from the server and responds with an ACK packet. 3 EDITED BY: PAWAN PANDEY

4 4.5 TCP WINDOW MANAGEMENT: Windowing and Window Size: Window management in TCP is an important concept that ensures reliability in packet delivery as well as reduce the wastage of time in waiting for the acknowledge after each packet. Window size: window size determines the amount of data that you can transmit before receiving an acknowledgment.sliding window refers to the fact that the window size is negotiated dynamically during the TCP session. 4.6 REMOTE PROCEDURE CALL: A program on one computer on a network uses a Remote Procedure Call to make a request of a program on another computer on the network without knowing the network's details. The RPC protocol is a network programming model for point-to-point communication within or between software applications. An RPC is also known as a subroutine call or a function call. In RPC, the sending computer makes a request in the form of a procedure, function, or method call. RPC translates these calls into requests and sends them over the network to the intended destination. The RPC recipient then processes the request based on the procedure name and argument list, and sends a response to the sender when complete. RPC applications typically implement software modules called "proxies" and "stubs" that broker the remote calls and make them appear to the programmer to be the same as local procedure calls. More recent examples of RPC technologies include Microsoft DCOM, Java RMI, and XML- RPC and SOAP. 4.7 DATA COMPRESSION TECHIQUES: Data compression squeezes data so it requires less disk space for storage and less bandwidth on a data transmission channel. Communications equipment like modems, bridges, and routers use compression schemes to improve throughput over standard phone lines or leased lines. Compression is also used to compress voice telephone calls transmitted over leased lines so that more calls can be placed on those lines. 4 EDITED BY: PAWAN PANDEY

Two important compression concepts are lossy and lossless compression: Lossy compression With lossy compression, it is assumed that some loss of information is acceptable.

5 Two important compression concepts are lossy and lossless compression: Lossy compression With lossy compression, it is assumed that some loss of information is acceptable. The best example is a videoconference where there is an acceptable amount of frame loss in order to deliver the image in real time. People may appear jerky in their movements, but you still have a grasp for what is happening on the other end of the conference. In the case of graphics files, some resolution may be lost in order to create a smaller file. The loss may be in the form of color depth or graphic detail. Lossless compression With lossless compression, data is compressed without any loss of data. It assumes you want to get everything back that you put in. Critical financial data files are examples where lossless compression is required Lossy compression can provide compression ratios of 100:1 to 200:1, depending on the type of information being compressed. Lossless compression ratios usually only achieve a 2:1 compression ratio. 4.8 CRYPTOGRAPHY: Cryptography is the science of using mathematics to encrypt and decrypt data. Cryptography enables you to store sensitive information or transmit it across insecure networks (like the Internet) so that it cannot be read by anyone except the intended recipient Public key cryptography Public key cryptography is an asymmetric scheme that uses a pair of keys for encryption: a public key, which encrypts data, and a corresponding private, or secret key for decryption. You publish your public key to the world while keeping your private key secret. Anyone with a copy of your public key can then encrypt information that only you can read. 5 EDITED BY: PAWAN PANDEY

4.8.2 Digital signatures A digital signature is

nearly impossible to counterfeit, plus it attests to

identity of the signer. 4.9 IEEE FORMAT : 4.9.1 802.

11 is the collection of standards set up for wireless

6 4.8.2 Digital signatures A digital signature is superior to a handwritten signature in that it is nearly impossible to counterfeit, plus it attests to the contents of the information as well as to the identity of the signer. 4.9 IEEE FORMAT : FORMAT is the collection of standards set up for wireless networking lives in the physical layer and data link layer in the OSI. 6 EDITED BY: PAWAN PANDEY

7 FORMAT IEEE uses CSMA/CD for Multiple Access which senses carrier before transmitting and listens for a collision while transmitting. When it detects collision it backs off and wait for random time and retransmit FORMAT A ring is first initialized by using a coordinator and the stations are inserted in the order of their address FORMAT IEEE uses token ring technique where a small frame called token is passed around the network. The node which passes the token can transmit data. If a node receiving the token has no information to send, it passes the token to the next end station. Each station can hold the token for a maximum period of time. 7 EDITED BY: PAWAN PANDEY

Operating Systems Design Exam 3 Review: Spring 2011

Operating Systems Design Exam 3 Review: Spring 2011 Paul Krzyzanowski pxk@cs.rutgers.edu 1 1. Why does an IP driver need to use ARP, the address resolution protocol? IP is a logical network. An IP address