A server algorithm that combines delayed allocation and pre-allocation can limit maximum concurrency levels. Delayed allocation reserves disk space for files but writes data to disk periodically rather than immediately. Pre-allocation reserves additional disk blocks upfront. To limit concurrency, the server restricts the number of concurrent client connections or operations that can be processed simultaneously.
This document provides an overview of SMTP (Simple Mail Transfer Protocol) including its history, general features, how it works, and limitations. SMTP is an Internet standard used to transfer email between Mail Transfer Agents (MTAs). It originated in 1980 and was standardized in 1981. Key points are that SMTP operates over TCP port 25 in a request-response format, uses status codes to indicate success or failure, and relies on MTAs like Sendmail to route and deliver messages between servers. However, it only supports basic 7-bit ASCII encoding and is susceptible to misuse like spamming.
This document discusses two common protocols for retrieving email from a server: POP3 and IMAP. POP3 allows a user to download emails from the server to their local device but does not support server-side functionality. IMAP allows users to access and manipulate emails stored on the server, avoiding delays from downloading. While POP3 is more widely used currently, IMAP offers advantages like folder management and searching that make it a preferable protocol.
TCP and UDP are transport layer protocols used for data transfer in the OSI model. TCP is connection-oriented, requiring a three-way handshake to establish a connection that maintains data integrity. It guarantees data will reach its destination without duplication but is slower than UDP. UDP is connectionless and used for applications requiring fast transmission like video calls, but does not ensure packet delivery and order. Both protocols add headers to packets with TCP focused on reliability and UDP on speed.
The document discusses the Transport layer protocols TCP and UDP. It describes TCP as a connection-oriented protocol that provides reliable, ordered delivery of streams of data through mechanisms like sequencing, acknowledgment, flow control and error checking. UDP is described as a simpler connectionless protocol that provides best-effort delivery without checking for errors or lost packets. The key concepts of ports, sockets, multiplexing and demultiplexing are also covered, as well as the header formats and functions of TCP and UDP.
The document discusses the User Datagram Protocol (UDP). It provides the following key points:
- UDP is an alternative to TCP that offers a limited connectionless datagram service for delivery of messages between devices on an IP network. It does not guarantee delivery, order of packets, or duplicate protection like TCP.
- UDP is commonly used for applications that require low latency and minimal processing time like DNS, SNMP, and streaming media. These applications can tolerate some data loss since reliability is not critical.
- The UDP header is only 8 bytes, containing source/destination port numbers and length fields. It provides an optional checksum for error detection but no other reliability mechanisms.
Tcp vs udp difference and comparison diffenHarikiran Raju
The document compares TCP and UDP protocols. TCP is connection-oriented and ensures reliable, ordered delivery of data. It is slower than UDP but suited for applications requiring high reliability. UDP is connectionless and does not guarantee delivery, order, or error checking. It is faster than TCP but less reliable. Examples of TCP applications include web browsing and file transfer. UDP is commonly used for applications requiring fast transmission like games and streaming media.
Transport layer protocols provide services like reliable data transfer and connection establishment between applications on networked devices. They address this need through protocols like TCP and UDP. TCP provides reliable, ordered data streams using mechanisms like three-way handshake, sequence numbers, acknowledgments, retransmissions, flow control via sliding windows, and connection termination handshaking. UDP provides simple datagram transmissions without reliability or flow control.
This document provides an overview of SMTP (Simple Mail Transfer Protocol) including its history, general features, how it works, and limitations. SMTP is an Internet standard used to transfer email between Mail Transfer Agents (MTAs). It originated in 1980 and was standardized in 1981. Key points are that SMTP operates over TCP port 25 in a request-response format, uses status codes to indicate success or failure, and relies on MTAs like Sendmail to route and deliver messages between servers. However, it only supports basic 7-bit ASCII encoding and is susceptible to misuse like spamming.
This document discusses two common protocols for retrieving email from a server: POP3 and IMAP. POP3 allows a user to download emails from the server to their local device but does not support server-side functionality. IMAP allows users to access and manipulate emails stored on the server, avoiding delays from downloading. While POP3 is more widely used currently, IMAP offers advantages like folder management and searching that make it a preferable protocol.
TCP and UDP are transport layer protocols used for data transfer in the OSI model. TCP is connection-oriented, requiring a three-way handshake to establish a connection that maintains data integrity. It guarantees data will reach its destination without duplication but is slower than UDP. UDP is connectionless and used for applications requiring fast transmission like video calls, but does not ensure packet delivery and order. Both protocols add headers to packets with TCP focused on reliability and UDP on speed.
The document discusses the Transport layer protocols TCP and UDP. It describes TCP as a connection-oriented protocol that provides reliable, ordered delivery of streams of data through mechanisms like sequencing, acknowledgment, flow control and error checking. UDP is described as a simpler connectionless protocol that provides best-effort delivery without checking for errors or lost packets. The key concepts of ports, sockets, multiplexing and demultiplexing are also covered, as well as the header formats and functions of TCP and UDP.
The document discusses the User Datagram Protocol (UDP). It provides the following key points:
- UDP is an alternative to TCP that offers a limited connectionless datagram service for delivery of messages between devices on an IP network. It does not guarantee delivery, order of packets, or duplicate protection like TCP.
- UDP is commonly used for applications that require low latency and minimal processing time like DNS, SNMP, and streaming media. These applications can tolerate some data loss since reliability is not critical.
- The UDP header is only 8 bytes, containing source/destination port numbers and length fields. It provides an optional checksum for error detection but no other reliability mechanisms.
Tcp vs udp difference and comparison diffenHarikiran Raju
The document compares TCP and UDP protocols. TCP is connection-oriented and ensures reliable, ordered delivery of data. It is slower than UDP but suited for applications requiring high reliability. UDP is connectionless and does not guarantee delivery, order, or error checking. It is faster than TCP but less reliable. Examples of TCP applications include web browsing and file transfer. UDP is commonly used for applications requiring fast transmission like games and streaming media.
Transport layer protocols provide services like reliable data transfer and connection establishment between applications on networked devices. They address this need through protocols like TCP and UDP. TCP provides reliable, ordered data streams using mechanisms like three-way handshake, sequence numbers, acknowledgments, retransmissions, flow control via sliding windows, and connection termination handshaking. UDP provides simple datagram transmissions without reliability or flow control.
TCP is a connection-oriented, reliable transport protocol that provides stream delivery, connection-oriented, and reliable services. It uses sequence numbers, acknowledgment numbers, and other features like flow control, error control, and congestion control to reliably deliver data between two endpoints. A TCP connection involves three phases - connection establishment using a three-way handshake, reliable data transfer with acknowledgments, and connection termination with another three-way handshake or four-way handshake with half-close option. TCP works well for both low and high-speed networks.
This document provides an overview of the User Datagram Protocol (UDP). It discusses UDP's attributes that make it suited for certain applications like streaming media. It describes UDP's packet structure including header fields like source/destination ports and checksum. It also compares UDP to the Transmission Control Protocol (TCP), noting that UDP does not guarantee delivery or ordering while TCP provides reliability. The document provides examples of applications that commonly use UDP like DNS and VoIP.
DNS translates domain names like www.google.com to IP addresses so that internet resources can be accessed in a meaningful way independent of location. HTTP defines how web pages are requested and transmitted between browsers and servers, such as when typing a website domain into the browser address bar. FTP and SMTP are protocols for transferring files and email messages between servers.
The application layer allows users to interface with networks through application layer protocols like HTTP, SMTP, POP3, FTP, Telnet, and DHCP. It provides the interface between applications on different ends of a network. Common application layer protocols include DNS for mapping domain names to IP addresses, HTTP for transferring web page data, and SMTP/POP3 for sending and receiving email messages. The client/server and peer-to-peer models describe how requests are made and fulfilled over the application layer.
Here are explanations of the requested concepts:
1. SMTP (Simple Mail Transfer Protocol):
- Used for sending and receiving email messages between servers
- Works on TCP port 25
- Client (email sender) connects to SMTP server and sends the email
- SMTP server then handles delivering the email to recipient's SMTP server
2. POP (Post Office Protocol):
- Used for retrieving email from a remote server to a local machine
- Works on TCP port 110 (POP3)
- User must first authenticate with their username and password
- POP downloads all emails from the server to the local machine
- Emails are then deleted from the server by default
3. IMAP (Internet Message Access Protocol):
This document provides an overview of the Simple Mail Transfer Protocol (SMTP). It begins with an introduction that defines SMTP and its use for electronic mail transmission. It then covers the working of SMTP, including the client-server model, commands, responses, and mail transfer phases of connection setup, mail transfer, and connection termination. It also provides a comparison of SMTP to HTTP, noting differences in how each protocol transfers files and initiates TCP connections. In summary, the document outlines the key components and functionality of the SMTP protocol for electronic mail transmission across the internet.
The document discusses several internet protocols including IP, HTTP, HTTPS, FTP, POP3, IMAP, SMTP, and MIME. IP defines how data is sent between computers on the internet using packets. HTTP and HTTPS govern how data is exchanged over the world wide web, with HTTPS providing encryption. FTP, POP3, IMAP, and SMTP define standards for file transfer and email transmission, storage, and access between servers and clients. MIME extended email to allow transmission of non-text files.
The transport layer provides end-to-end communication between processes on different machines. Two main transport protocols are TCP and UDP. TCP provides reliable, connection-oriented data transmission using acknowledgments and retransmissions. UDP provides simpler, connectionless transmission but without reliability. Both protocols use port numbers to identify processes and negotiate quality of service options during connection establishment.
SMTP is the standard protocol for sending emails between servers. Under SMTP, a client SMTP process opens a TCP connection to a remote server SMTP process and sends mail across the connection. The server listens on port 25 for connections. When a connection is made, the two processes execute a simple request-response dialogue defined by SMTP to transmit sender and recipient addresses and the email message itself. Mail is then forwarded to remote servers or delivered locally. POP3 and IMAP allow users to download stored mail from the local server.
There are two main internet protocols: TCP and UDP. TCP is connection-oriented and reliable, ensuring packets are delivered in order. It is slower than UDP but suited for applications like web browsing where reliability is important. UDP is connectionless and faster but packets may arrive out of order or not at all, making it well-suited for real-time applications like games and streaming media. Key differences between the two protocols include their handling of connections, ordering of packets, speed, and reliability of delivery.
What is the difference between udp and tcp internet protocols krupalipandya29
UDP and TCP are internet protocols that operate at the transport layer. TCP is connection-oriented and reliable, ensuring delivered messages arrive in order. It is used for applications like web and email. UDP is connectionless and unreliable, providing no guarantee of delivery or message ordering. It is used for applications requiring speed like streaming media.
TCP and UDP use ports to direct data packages to applications. Ports are numbered openings that operating systems use to direct incoming data to the correct destination. Common port numbers include 80 for HTTP, 443 for HTTPS, 22 for SSH, and 25 for SMTP. Protocols like HTTP and HTTPS operate at the application layer and use plain text requests and responses, while HTTPS additionally implements encryption through SSL to secure the connection.
Jaimin chp-6 - transport layer- 2011 batchJaimin Jani
The document discusses the transport layer in computer networking. It explains that the transport layer provides logical communication between processes running on different hosts. It describes two main transport protocols: TCP and UDP. TCP provides connection-oriented transmission that is reliable and in-order, while UDP provides connectionless transmission that is unreliable and unordered. The document also covers topics like connection establishment, port numbers, sockets, and services provided by the transport layer.
This document provides an overview of internet protocols for email (SMTP) including:
- SMTP is used to transfer email between servers and works in a client-server model. Email clients use POP3 or IMAP to retrieve messages from servers.
- Key components include user agents (email clients), message transfer agents (MTA servers), and protocols like SMTP, POP3, and IMAP.
- SMTP uses a stored-and-forward method to route emails through intermediate servers within a network on its way to the destination address.
TCP and UDP are transport layer protocols that package and deliver data between applications. TCP provides reliable, ordered delivery through connection establishment and packet sequencing. UDP provides faster, unreliable datagram delivery without connections. Common applications using TCP include HTTP, FTP, and SMTP. Common UDP applications include DNS, DHCP, and streaming media.
This document provides an overview of various application layer protocols including electronic mail (SMTP, POP3, IMAP), HTTP, web services, DNS, and SNMP. It discusses the distinction between application programs and protocols, how protocols implement remote procedure calls, and that protocols have companion protocols that define message formats. Specific protocols covered in more detail include SMTP for mail transfer, POP3 and IMAP for mail access, HTTP for web access, and the general functions of DNS and SNMP in networks.
RPC allows a program to call a subroutine that resides on a remote machine. When a call is made, the calling process is suspended and execution takes place on the remote machine. The results are then returned. This makes the remote call appear local to the programmer. RPC uses message passing to transmit information between machines and allows communication between processes on different machines or the same machine. It provides a simple interface like local procedure calls but involves more overhead due to network communication.
UDP and TCP Protocol & Encrytion and its algorithmAyesha Tahir
The document discusses the TCP/IP protocol suite and the UDP and TCP transport layer protocols. UDP is a connectionless, unreliable protocol that provides basic process-to-process communication with minimal overhead. TCP is a connection-oriented, reliable protocol that establishes virtual connections between processes, provides reliable in-order data delivery through flow and error control mechanisms, and allows processes to communicate via data streams. Both protocols use port numbers to identify communicating processes and encapsulate data in IP datagrams for transmission.
AD, DNS, DHCP, HTTP, HTTPS, SMTP, POP3 and FTP use specific port numbers. The FTP server accepts incoming FTP requests and copies files to a publishing folder for access over the network. Virtual hosting refers to multiple websites hosted on one server, with each site virtually shared and not dedicated. Cloud computing infrastructure differs from traditional client-server models by using a main cloud controller and worker nodes/clusters to process requests from clients.
The document discusses processes and threads in distributed systems. It explains that threads allow multiple executions within the same process by sharing resources like memory. Distributed systems can use multithreaded clients and servers to improve performance. Code migration is also discussed, where a program's code and execution state can be moved between machines for better load balancing or to reduce communication costs. The challenges of migrating local resources that may be fixed to a particular machine are also covered.
TCP is a connection-oriented, reliable transport protocol that provides stream delivery, connection-oriented, and reliable services. It uses sequence numbers, acknowledgment numbers, and other features like flow control, error control, and congestion control to reliably deliver data between two endpoints. A TCP connection involves three phases - connection establishment using a three-way handshake, reliable data transfer with acknowledgments, and connection termination with another three-way handshake or four-way handshake with half-close option. TCP works well for both low and high-speed networks.
This document provides an overview of the User Datagram Protocol (UDP). It discusses UDP's attributes that make it suited for certain applications like streaming media. It describes UDP's packet structure including header fields like source/destination ports and checksum. It also compares UDP to the Transmission Control Protocol (TCP), noting that UDP does not guarantee delivery or ordering while TCP provides reliability. The document provides examples of applications that commonly use UDP like DNS and VoIP.
DNS translates domain names like www.google.com to IP addresses so that internet resources can be accessed in a meaningful way independent of location. HTTP defines how web pages are requested and transmitted between browsers and servers, such as when typing a website domain into the browser address bar. FTP and SMTP are protocols for transferring files and email messages between servers.
The application layer allows users to interface with networks through application layer protocols like HTTP, SMTP, POP3, FTP, Telnet, and DHCP. It provides the interface between applications on different ends of a network. Common application layer protocols include DNS for mapping domain names to IP addresses, HTTP for transferring web page data, and SMTP/POP3 for sending and receiving email messages. The client/server and peer-to-peer models describe how requests are made and fulfilled over the application layer.
Here are explanations of the requested concepts:
1. SMTP (Simple Mail Transfer Protocol):
- Used for sending and receiving email messages between servers
- Works on TCP port 25
- Client (email sender) connects to SMTP server and sends the email
- SMTP server then handles delivering the email to recipient's SMTP server
2. POP (Post Office Protocol):
- Used for retrieving email from a remote server to a local machine
- Works on TCP port 110 (POP3)
- User must first authenticate with their username and password
- POP downloads all emails from the server to the local machine
- Emails are then deleted from the server by default
3. IMAP (Internet Message Access Protocol):
This document provides an overview of the Simple Mail Transfer Protocol (SMTP). It begins with an introduction that defines SMTP and its use for electronic mail transmission. It then covers the working of SMTP, including the client-server model, commands, responses, and mail transfer phases of connection setup, mail transfer, and connection termination. It also provides a comparison of SMTP to HTTP, noting differences in how each protocol transfers files and initiates TCP connections. In summary, the document outlines the key components and functionality of the SMTP protocol for electronic mail transmission across the internet.
The document discusses several internet protocols including IP, HTTP, HTTPS, FTP, POP3, IMAP, SMTP, and MIME. IP defines how data is sent between computers on the internet using packets. HTTP and HTTPS govern how data is exchanged over the world wide web, with HTTPS providing encryption. FTP, POP3, IMAP, and SMTP define standards for file transfer and email transmission, storage, and access between servers and clients. MIME extended email to allow transmission of non-text files.
The transport layer provides end-to-end communication between processes on different machines. Two main transport protocols are TCP and UDP. TCP provides reliable, connection-oriented data transmission using acknowledgments and retransmissions. UDP provides simpler, connectionless transmission but without reliability. Both protocols use port numbers to identify processes and negotiate quality of service options during connection establishment.
SMTP is the standard protocol for sending emails between servers. Under SMTP, a client SMTP process opens a TCP connection to a remote server SMTP process and sends mail across the connection. The server listens on port 25 for connections. When a connection is made, the two processes execute a simple request-response dialogue defined by SMTP to transmit sender and recipient addresses and the email message itself. Mail is then forwarded to remote servers or delivered locally. POP3 and IMAP allow users to download stored mail from the local server.
There are two main internet protocols: TCP and UDP. TCP is connection-oriented and reliable, ensuring packets are delivered in order. It is slower than UDP but suited for applications like web browsing where reliability is important. UDP is connectionless and faster but packets may arrive out of order or not at all, making it well-suited for real-time applications like games and streaming media. Key differences between the two protocols include their handling of connections, ordering of packets, speed, and reliability of delivery.
What is the difference between udp and tcp internet protocols krupalipandya29
UDP and TCP are internet protocols that operate at the transport layer. TCP is connection-oriented and reliable, ensuring delivered messages arrive in order. It is used for applications like web and email. UDP is connectionless and unreliable, providing no guarantee of delivery or message ordering. It is used for applications requiring speed like streaming media.
TCP and UDP use ports to direct data packages to applications. Ports are numbered openings that operating systems use to direct incoming data to the correct destination. Common port numbers include 80 for HTTP, 443 for HTTPS, 22 for SSH, and 25 for SMTP. Protocols like HTTP and HTTPS operate at the application layer and use plain text requests and responses, while HTTPS additionally implements encryption through SSL to secure the connection.
Jaimin chp-6 - transport layer- 2011 batchJaimin Jani
The document discusses the transport layer in computer networking. It explains that the transport layer provides logical communication between processes running on different hosts. It describes two main transport protocols: TCP and UDP. TCP provides connection-oriented transmission that is reliable and in-order, while UDP provides connectionless transmission that is unreliable and unordered. The document also covers topics like connection establishment, port numbers, sockets, and services provided by the transport layer.
This document provides an overview of internet protocols for email (SMTP) including:
- SMTP is used to transfer email between servers and works in a client-server model. Email clients use POP3 or IMAP to retrieve messages from servers.
- Key components include user agents (email clients), message transfer agents (MTA servers), and protocols like SMTP, POP3, and IMAP.
- SMTP uses a stored-and-forward method to route emails through intermediate servers within a network on its way to the destination address.
TCP and UDP are transport layer protocols that package and deliver data between applications. TCP provides reliable, ordered delivery through connection establishment and packet sequencing. UDP provides faster, unreliable datagram delivery without connections. Common applications using TCP include HTTP, FTP, and SMTP. Common UDP applications include DNS, DHCP, and streaming media.
This document provides an overview of various application layer protocols including electronic mail (SMTP, POP3, IMAP), HTTP, web services, DNS, and SNMP. It discusses the distinction between application programs and protocols, how protocols implement remote procedure calls, and that protocols have companion protocols that define message formats. Specific protocols covered in more detail include SMTP for mail transfer, POP3 and IMAP for mail access, HTTP for web access, and the general functions of DNS and SNMP in networks.
RPC allows a program to call a subroutine that resides on a remote machine. When a call is made, the calling process is suspended and execution takes place on the remote machine. The results are then returned. This makes the remote call appear local to the programmer. RPC uses message passing to transmit information between machines and allows communication between processes on different machines or the same machine. It provides a simple interface like local procedure calls but involves more overhead due to network communication.
UDP and TCP Protocol & Encrytion and its algorithmAyesha Tahir
The document discusses the TCP/IP protocol suite and the UDP and TCP transport layer protocols. UDP is a connectionless, unreliable protocol that provides basic process-to-process communication with minimal overhead. TCP is a connection-oriented, reliable protocol that establishes virtual connections between processes, provides reliable in-order data delivery through flow and error control mechanisms, and allows processes to communicate via data streams. Both protocols use port numbers to identify communicating processes and encapsulate data in IP datagrams for transmission.
AD, DNS, DHCP, HTTP, HTTPS, SMTP, POP3 and FTP use specific port numbers. The FTP server accepts incoming FTP requests and copies files to a publishing folder for access over the network. Virtual hosting refers to multiple websites hosted on one server, with each site virtually shared and not dedicated. Cloud computing infrastructure differs from traditional client-server models by using a main cloud controller and worker nodes/clusters to process requests from clients.
The document discusses processes and threads in distributed systems. It explains that threads allow multiple executions within the same process by sharing resources like memory. Distributed systems can use multithreaded clients and servers to improve performance. Code migration is also discussed, where a program's code and execution state can be moved between machines for better load balancing or to reduce communication costs. The challenges of migrating local resources that may be fixed to a particular machine are also covered.
This document discusses processes and threads in distributed systems. It covers how threads allow multitasking within a process by sharing resources. Threads can be implemented in either userspace or kernelspace. Distributed systems can use multithreaded clients and servers. Code migration involves moving a running program between machines for load balancing, reducing communication, or dynamic configuration. Weak mobility transfers just code, while strong mobility also moves execution state. References to local resources must also be handled during migration.
Inter process communication by Dr.C.R.Dhivyaa, Assistant Professor,Kongu Engi...Dhivyaa C.R
Interprocess Communication: The API for the Internet Protocols – External data representation and marshalling – Client– server communication – Group communication. Distributed Objects – Communication between distributed objects – Remote procedure call.
This document discusses various topics related to computer networking including routing, addressing schemes, congestion control, remote procedure calls, simple mail transfer protocol, static routing algorithms, IPv4 addressing, and session layer design issues. It provides definitions and explanations of static and dynamic routing, differentiates between IPv4 and IPv6 addressing, describes congestion and congestion control, discusses the importance and workings of remote procedure calls, provides a detailed explanation of SMTP, explains two static routing algorithms (Dijkstra's algorithm and flooding algorithm), discusses IPv4 addressing schemes, describes congestion avoidance in the transport layer, and discusses design issues of the session layer such as dialog control.
This document summarizes key concepts about the transport layer in computer networks. It discusses:
1. The transport layer is responsible for process-to-process delivery of data across a network. This involves delivering packets from one process to another, often using a client-server model.
2. There are two main transport layer protocols - UDP, which is a connectionless and unreliable protocol, and TCP, which establishes connections and provides reliable data delivery.
3. TCP and UDP use port numbers along with IP addresses to uniquely identify processes. TCP also implements flow and error control to ensure reliable data transfer.
1. Malware - Malicious software like viruses, ransomware, spyware that infect devices.
2. Denial of Service (DoS) - Floods networks/servers with traffic to overload them. Distributed DoS (DDoS) uses multiple infected devices.
3. Man-in-the-Middle (MITM) - Hackers intercept communications between two parties to steal data or install malware. Often occurs on public WiFi.
4. Phishing - Deceptive communications like emails trick users into revealing sensitive info or installing malware.
5. SQL Injection - Malicious code inserted into databases to steal info or
The document discusses denial of service (DoS) and distributed denial of service (DDoS) attacks. It describes different types of DoS attacks such as sending malformed packets to exploit protocol or application flaws. It notes that DDoS attacks involve aggregating malicious traffic from many zombie machines to flood the victim with packets. Most defense methods focus on mitigating bandwidth consumption from packet flooding. However, attackers may also directly target applications to exhaust computational resources. The document proposes an acknowledgment-based port hopping protocol for secure communication between a sender and receiver that is resistant to such attacks.
The Java Mail Server project allows clients to connect to a mail server to send and receive emails and attachments. The project is divided into three modules: a server module that uses server sockets to accept client connections, a client module that uses sockets to connect to the server, and an email inbox module that handles mail functions like forwarding, viewing attachments, and saving emails. The server stores details of client connections, mail sending and receiving. Clients can connect when the server is active to exchange emails with other clients. Usernames and passwords are stored in data files rather than a SQL server. The project provides automatic threading to handle socket connections and includes features for reliable TCP communication between clients.
The transport layer provides efficient, reliable, and cost-effective process-to-process delivery by making use of network layer services. The transport layer works through transport entities to achieve its goal of reliable delivery between application processes. It provides an interface for applications to access its services.
This document provides information about the Networks Laboratory course offered at Anjalai Ammal Mahalingam Engineering College. It includes the syllabus, list of experiments, objectives and outcomes of the course. The course aims to teach students socket programming, simulation tools, and hands-on experience with networking protocols. Some key experiments include implementing stop-and-wait and sliding window protocols, socket programming, simulating ARP/RARP, PING and traceroute, and studying routing algorithms. The course is intended to help students use simulation tools, implement protocols, and analyze network performance and routing.
The transport layer chapter discusses process-to-process delivery and the transport layer protocols TCP and UDP. TCP provides reliable, connection-oriented data transfer using sequencing, acknowledgements and retransmissions. UDP provides simpler, connectionless delivery without reliability. Well-known ports are assigned for standard services like DNS, HTTP, FTP. TCP uses sliding windows and congestion control to prevent overwhelming the receiver. Reliability and flow control are implemented end-to-end rather than just link-by-link.
The document discusses remote procedure call (RPC), including its definition and purpose, execution steps when making an RPC, how clients connect to servers, issues around transparency, call semantics, data representation, performance, security, and how to write RPC programs. RPC allows programs to execute subroutines remotely by hiding network details in stub procedures, making remote calls similar to local calls. The Sun RPC implementation is described as an example.
Network protocols allow connected devices to communicate regardless of differences. A protocol is a set of rules that govern all aspects of communication between peers. Common network protocols include TCP, UDP, ICMP, and HTTP. TCP establishes connections to reliably deliver data. UDP prioritizes speed over reliability. ICMP reports network errors while HTTP transfers web page content. Together these protocols enable the functioning of the internet.
How a network connection is created A network connection is initi.pdfarccreation001
How a network connection is created ?
A network connection is initiated by a client program when it creates a socket for the
communication with the server. To create the socket in Java, the client calls the Socket
constructor and passes the server address and the the specific server port number to it. At this
stage the server must be started on the machine having the specified address and listening for
connections on its specific port number.
The server uses a specific port dedicated only to listening for connection requests from clients. It
can not use this specific port for data communication with the clients because the server must be
able to accept the client connection at any instant. So, its specific port is dedicated only to
listening for new connection requests. The server side socket associated with specific port is
called server socket. When a connection request arrives on this socket from the client side, the
client and the server establish a connection. This connection is established as follows:
The java.net package in the Java development environment provides the class Socket that
implements the client side and the class serverSocket class that implements the server side
sockets.
The client and the server must agree on a protocol. They must agree on the language of the
information transferred back and forth through the socket. There are two communication
protocols :
The stream communication protocol is known as TCP (transfer control protocol). TCP is a
connection-oriented protocol. It works as described in this document. In order to communicate
over the TCP protocol, a connection must first be established between two sockets. While one of
the sockets listens for a connection request (server), the other asks for a connection (client). Once
the two sockets are connected, they can be used to transmit and/or to receive data. When we say
\"two sockets are connected\" we mean the fact that the server accepted a connection. As it was
explained above the server creates a new local socket for the new connection. The process of the
new local socket creation, however, is transparent for the client.
The datagram communication protocol, known as UDP (user datagram protocol), is a
connectionless protocol. No connection is established before sending the data. The data are sent
in a packet called datagram. The datagram is sent like a request for establishing a connection.
However, the datagram contains not only the addresses, it contains the user data also. Once it
arrives to the destination the user data are read by the remote application and no connection is
established. This protocol requires that each time a datagram is sent, the local socket and the
remote socket addresses must also be sent in the datagram. These addresses are sent in each
datagram.
The java.net package in the Java development environment provides the class DatagramSocket
for programming datagram communications.
UDP is an unreliable protocol. There is no guarantee that the .
The document provides information about various networking concepts and protocols. It contains 26 questions and answers about topics such as IGMP, ping, tracert, RSVP, DHCP, domains vs workgroups, NAT, PPP, IP spoofing, IP datagrams, application gateways, circuit gateways, default gateways, LANs, intranets vs the Internet, protocols, FTP, the OSI model layers, network types, topologies, IP, TCP, UDP, IP addressing classes, multicasting, DNS, telnet, and SMTP. It also defines MAC addresses.
Unit 3 - Protocols and Client-Server Applications - ITDeepraj Bhujel
The document summarizes several internet protocols used for communication over IP networks:
SMTP is used for email transmission and uses TCP port 25. It allows for mail, recipient, and data commands in a transaction. POP and IMAP are used for retrieving email from servers, with POP deleting emails from the server and IMAP leaving them on the server. HTTP is the underlying protocol for the web and uses port 80. FTP uses ports 20 and 21 for data and control connections. PGP provides encryption for email. Client-server and n-tier architectures partition tasks between clients and servers. Multiple protocols are needed for complex network communication due to hardware failures, congestion, and other issues.
This document discusses Java networking and client/server communication. A client machine makes requests to a server machine over a network using protocols like TCP and UDP. TCP provides reliable data transmission while UDP sends independent data packets. Port numbers map incoming data to running processes. Sockets provide an interface for programming networks, with ServerSocket and Socket classes in Java. A server program listens on a port for client connections and exchanges data through input/output streams. Servlets extend web server functionality by executing Java programs in response to client requests.
Introduction to the client server computing By Attaullah HazratAttaullah Hazrat
This document is a student's term paper on client server computing. It contains an introduction to client server models and discusses different types of servers like file servers, print servers, application servers, and more. It also describes the differences between thin and fat clients and servers, with the current trend being towards fat servers and thin clients. The document provides details on various aspects of client server systems for the student's course assignment.
Have you ever been confused by the myriad of choices offered by AWS for hosting a website or an API?
Lambda, Elastic Beanstalk, Lightsail, Amplify, S3 (and more!) can each host websites + APIs. But which one should we choose?
Which one is cheapest? Which one is fastest? Which one will scale to meet our needs?
Join me in this session as we dive into each AWS hosting service to determine which one is best for your scenario and explain why!
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Webinar Recording: https://www.panagenda.com/webinars/hcl-notes-and-domino-license-cost-reduction-in-the-world-of-dlau/
The introduction of DLAU and the CCB & CCX licensing model caused quite a stir in the HCL community. As a Notes and Domino customer, you may have faced challenges with unexpected user counts and license costs. You probably have questions on how this new licensing approach works and how to benefit from it. Most importantly, you likely have budget constraints and want to save money where possible. Don’t worry, we can help with all of this!
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These topics will be covered
- Reducing license cost by finding and fixing misconfigurations and superfluous accounts
- How do CCB and CCX licenses really work?
- Understanding the DLAU tool and how to best utilize it
- Tips for common problem areas, like team mailboxes, functional/test users, etc
- Practical examples and best practices to implement right away
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Webinar Recording: https://www.panagenda.com/webinars/hcl-notes-und-domino-lizenzkostenreduzierung-in-der-welt-von-dlau/
DLAU und die Lizenzen nach dem CCB- und CCX-Modell sind für viele in der HCL-Community seit letztem Jahr ein heißes Thema. Als Notes- oder Domino-Kunde haben Sie vielleicht mit unerwartet hohen Benutzerzahlen und Lizenzgebühren zu kämpfen. Sie fragen sich vielleicht, wie diese neue Art der Lizenzierung funktioniert und welchen Nutzen sie Ihnen bringt. Vor allem wollen Sie sicherlich Ihr Budget einhalten und Kosten sparen, wo immer möglich. Das verstehen wir und wir möchten Ihnen dabei helfen!
Wir erklären Ihnen, wie Sie häufige Konfigurationsprobleme lösen können, die dazu führen können, dass mehr Benutzer gezählt werden als nötig, und wie Sie überflüssige oder ungenutzte Konten identifizieren und entfernen können, um Geld zu sparen. Es gibt auch einige Ansätze, die zu unnötigen Ausgaben führen können, z. B. wenn ein Personendokument anstelle eines Mail-Ins für geteilte Mailboxen verwendet wird. Wir zeigen Ihnen solche Fälle und deren Lösungen. Und natürlich erklären wir Ihnen das neue Lizenzmodell.
Nehmen Sie an diesem Webinar teil, bei dem HCL-Ambassador Marc Thomas und Gastredner Franz Walder Ihnen diese neue Welt näherbringen. Es vermittelt Ihnen die Tools und das Know-how, um den Überblick zu bewahren. Sie werden in der Lage sein, Ihre Kosten durch eine optimierte Domino-Konfiguration zu reduzieren und auch in Zukunft gering zu halten.
Diese Themen werden behandelt
- Reduzierung der Lizenzkosten durch Auffinden und Beheben von Fehlkonfigurationen und überflüssigen Konten
- Wie funktionieren CCB- und CCX-Lizenzen wirklich?
- Verstehen des DLAU-Tools und wie man es am besten nutzt
- Tipps für häufige Problembereiche, wie z. B. Team-Postfächer, Funktions-/Testbenutzer usw.
- Praxisbeispiele und Best Practices zum sofortigen Umsetzen
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Programming Foundation Models with DSPy - Meetup Slides
Internet
1. INTERNATIONAL INSTITUTE OF MANAGEMENT AND
TECHNICAL STUDIES
INTERNET
All the questions are compulsory. The first five questions shall be of 16 marks each and
the last question shall be of 20 marks.
Q1. A. Should a client use the same protocol port number each time it begins? Why or why
not?
Servers are normally known by their well-known port number. For example, every TCP/IP
implementation that provides an FTP server provides that service on TCP port 21. Every Telnet
server is on TCP port 23. Every implementation of TFTP (the Trivial File Transfer Protocol) is on
UDP port 69. Those services that can be provided by any implementation of TCP/IP have well-
known port numbers between 1 and 1023. The well-known ports are managed by the Internet
Assigned Numbers Authority (IANA).
A client usually doesn't care what port number it uses on its end. All it needs to be certain
of is that whatever port number it uses be unique on its host. Client port numbers are
called ephemeral ports (i.e., short lived). This is because a client typically exists only as long
as the user running the client needs its service, while servers typically run as long as the host
is up.
A "port" is just a number. All a "connection to a port" really represents is a packet which has
that number specified in its "destination port" header field. For a stateless protocol (UDP), there
is no problem because "connections" don't exist - multiple people can send packets to the same
port, and their packets will arrive in whatever sequence. Nobody is ever in the "connected" state.
For a stateful protocol (like TCP), a connection is identified by a 4-tuple consisting of source
and destination ports and source and destination IP addresses. So, if two different machines
connect to the same port on a third machine, there are two distinct connections because the
source IPs differ. If the same machine (or two behind NAT or otherwise sharing the same IP
address) connects twice to a single remote end, the connections are differentiated by source
port (which is generally a random high-numbered port).
Simply, if I connect to the same web server twice from my client, the two connections will
have different source ports from my perspective and destination ports from the web servers. So
2. there is no ambiguity, even though both connections have the same source and destination IP
addresses.
Ports are a way to multiplex IP addresses so that different applications can listen on the same
IP address/protocol pair. Unless an application defines its own higher-level protocol, there is no
way to multiplex a port. If two connections using the same protocol have identical source and
destination IPs and identical source and destination ports, they must be the same connection.
When an Ethernet frame is received at the destination host it starts its way up the protocol
stack and all the headers are removed by the appropriate protocol box. Each protocol box looks
at certain identifiers in its header to determine which box in the next upper layer receives the
data. This is called demultiplexing.
Most networking applications are written assuming one side is the client and the other the
server. The purpose of the application is for the server to provide some defined service for
clients.
We can categorize servers into two classes: iterative or concurrent. An iterative server iterates
through the following steps.
I1. Wait for a client request to arrive.
I2. Process the client request.
I3. Send the response back to the client that sent the request.
I4. Go back to step I1.
The problem with an iterative server is when step I2 takes a while. During this time no other
clients are serviced. A concurrent server, on the other hand, performs the following steps.
Cl. Wait for a client request to arrive.
C2. Start a new server to handle this client's request. This may involve creating a new process,
task, or thread, depending on what the underlying operating system supports. How this step is
performed depends on the operating system.
This new server handles this client's entire request. When complete, this new server
terminates.
C3. Go back to step Cl.
3. The advantage of a concurrent server is that the server just spawns other servers to handle
the client requests. Each client has, in essence, its own server. Assuming the operating system
allows multiprogramming, multiple clients are serviced concurrently.
The reason we categorize servers, and not clients, is because a client normally can't tell
whether it's talking to an iterative server or a concurrent server.
As a general rule, TCP servers are concurrent, and UDP servers are iterative, but there are a
few exceptions.
B. Write a program that uses “execve” to change the code a process executes?
main()
{
char *arg[]={"AA", "BB",0}; //these are the array of arguments which may include program
name
char *env[]={ "PATH=/home/xyx", "ENV=/***/***", 0}; List of nvironmentvariables
execve("executafilepathinformations, arg, env);
}
Q2. Write down the data structures and message formats needed for a stateless file server.
What happens if two or more clients access the same file? What happens if a client
crashes before closing a file?
A stateless system is one in which the client sends a request to a server, the server carries it out,
and returns the result. Between these requests, no client-specific information is stored on the
server. A stateful system is one where information about client connections is maintained on the
server. State may refer to any information that a server stores about a client: whether a file is open,
whether a file is being modified, cached data on the client, etc.
Statelessness in the context of servers, the question of whether a server is stateless or stateful
centers on the application protocol more than the implementation. If the application protocol
specifies that the meaning of a particular message depends in some way on previous messages, it
may be impossible to provide a stateless interaction.
In essence, the issue of statelessness focuses on whether the application protocol assumes
the responsibility for reliable delivery. To avoid problems and make the interaction reliable, an
application protocol designer must ensure that each message is completely unambiguous. That is,
a message cannot depend on being delivered in order, nor can it depend on previous messages
having been delivered. In essence, the protocol designer must build the interaction so the server
gives the same response no matter when or how many times a request arrives. Mathematicians
4. use the term idempotent to refer to a mathematical operation that always produces the same
result.
We use the term to refer to protocols that arrange for a server to give the same response to a
given message no matter how many times it arrives. In an internet where the underlying network
can duplicate, delay or deliver messages out of order or where computers running client
applications can crash unexpectedly, the server should be stateless. The server can only be
stateless if the application protocol is designed to make operations idempotent.
Message Creation and Stateless Operations
Data Structures
struct pjsip_send_state
struct pjsip_response_addr
Functions
pj_status_t
pjsip_endpt_send_request_stateless (pjsip_endpoint *endpt, pjsip_tx_data *tdata,void
*token, pjsip_send_callback cb)
Send outgoing request statelessly, the function will take care of which destination and
transport to use based on the information in the message, taking care of URI in the request line
and Route header.
This function is different than pjsip_transport_send() in that this function adds/modify the Via
header as necessary.
Parameters
endpt The endpoint instance.
tdata The transmit data to be sent.
token Arbitrary token to be given back on the callback.
Cb
Optional callback to notify transmission status (also gives chance for application
to discontinue retrying sending to alternate address).
Returns
PJ_SUCCESS, or the appropriate error code.
5. In a stateless system:
Each request must be complete — the file has to be fully identified and any offsets specified.
If a server crashes and then recovers, no state was lost about client connections because
there was no state to maintain. This creates a higher degree of fault tolerance.
No remote open/close calls are needed (they only serve to establish state).
There is no server memory devoted to storing per-client data.
There is no limit on the number of open files on the server; they aren't "open" since the
server maintains no per-client state.
There are no problems if the client crashes. The server does not have any state to clean up.
Q3. Write a server algorithm that combines delayed allocation with pre allocation. How can
you limit the maximum level of concurrency?
Delayed allocation
Allocation is setting aside, or reserving, space for use. On a computer, it is setting aside the
space on a hard drive for use to store files. The files can be newly created or those being
modified. Data which needs to be written to the harddisk can be saved in RAM or cache.
RAM/cache is able to read/write faster than hard drives. At certain intervals, the data is taken
from RAM/cache and written to the harddisk. The Writeback Time Interval sets how often the
writeback occurs. If there is a loss of power or the system is shut off, the data changes in the
RAM/cache are lost since they have not written to disk.
It is usually best to set the Writeback Time Interval to a lower time frame. The Delayed
Allocation is when the data blocks are written at the Writeback Time Interval.
There are three advantages to Delayed Allocation:
1. Larger sets of blocks are processed before being written. This reduces the processer utilization
by performing the processing all at once, as discussed in Multi-Block Allocation.
2. Reduces fragmentation by allocating a large number of blocks at once which are most likely
contiguous.
3. Reduces processor time and disk space for files that are short-term temporary files wich are
used and deleted in RAM/cache before they are written.
For files where the file size is unknown at the time of writing, usually since it is still being
modified or created, this is the best method.
6. It is a performance feature (it doesn't change the disk format) found in a few modern filesystems such
as XFS, ZFS, btrfs or Reiser 4, and it consists in delaying the allocation of blocks as much as possible,
contrary to what traditionally filesystems (such as Ext3, reiser3, etc) do: allocate the blocks as soon as
possible. For example, if a process write()s, the filesystem code will allocate immediately the blocks
where the data will be placed - even if the data is not being written right now to the disk and it's going
to be kept in the cache for some time. This approach has disadvantages. For example when a process
is writing continually to a file that grows, successive write()s allocate blocks for the data, but they don't
know if the file will keep growing. Delayed allocation, on the other hand, does not allocate the blocks
immediately when the process write()s, rather, it delays the allocation of the blocks while the file is kept
in cache, until it is really going to be written to the disk. This gives the block allocator the opportunity to
optimize the allocation in situations where the old system couldn't. Delayed allocation plays very nicely
with the two previous features mentioned, extents and multiblock allocation, because in many
workloads when the file is written finally to the disk it will be allocated in extents whose block allocation
is done with the mballoc allocator. The performance is much better, and the fragmentation is much
improved in some workloads.
7. Pre-Allocation
Similar to Delayed Allocation, the file is in RAM/cache, but the kernel will allocate the space
needed on the hard drive. The file is written with all zeroes and should hopefully be contiguous.
The method guarantees that the storage space is available for the file.
For files where the file sizes are known, then this method is the best because the set space
can be “reserved”.Keep in mind that if the file is accessed before it is written from RAM/cache, the
results will be a file of all bits set to zeroes.
Preallocation rules are processed before the placement rules.
8. When a file is created, the preallocation value from the policy will be used instead of the default
allocation of one block. The preallocation value is rounded up to the number of blocks required for the
specified amount. For example, a value of 1 byte can be specified, but SAN File System will allocate
one 4-kilobyte block. The maximum preallocation value is 128 megabytes.
Limiting Maximum Number of Concurrency
If your program uses webservices number of simultaneous connections will be limited
to ServicePointManager.DefaultConnectionLimit property. If you want 5 simultaneous
connections it is not enough to use Arrow_Raider's solution.
You also should increase ServicePointManager.DefaultConnectionLimit because it is only 2
by default.
We can use semaphores also to reduce the maximum number of concurrency.
private void RunAllActions(IEnumerable<Action> actions, int maxConcurrency)
{
using(SemaphoreSlim concurrencySemaphore = new emaphoreSlim(maxConcurrency))
{
foreach(Action action in actions)
{
Task.Factory.StartNew(() =>
{
concurrencySemaphore.Wait();
try
{
action();
}
Finally
{
concurrencySemaphore.Release();
}
});
}
}
}
Q4. A. Under what circumstances might a programmer need to pass opaque data objects
between a client and a server?
When you look at Security Builder Crypto function definitions, you will see there are a number
of data types whose names begin with sb_. These types are declared in sbdef.h, and are actually
pointers to undefined data structures. These pointers are used by the library to refer to internally-
9. defined structures. The actual definitions of the data structures are irrelevant, as they are only
used within the library. These types of data structures are often referred to as opaque or abstract
data types.
When creating and destroying these opaque data types, you must pass a pointer to
an sb_ type to the API function. For example, a pointer to an sb_Params or an sb_Keyobject. In
other cases, where the value of the pointer itself is not changed, you simply supply the value of
the sb_ type variables to the interface functions. In order to understand the function call
sequence, you must become familiar with the opaque data types, or objects.
Some objects cannot be created without other objects; they must be created and destroyed in
a particular order.
The main sb_ types are:
Global Context (sb_GlobalCtx)
Yield Context (sb_YieldCtx)
RNG Context (sb_RNGCtx)
Parameters Object (sb_Params)
Key Objects (sb_Key, sb_PublicKey, sb_PrivateKey)
SB Context (sb_Context)
In computer science, an opaque data type is a data type that is incompletely defined in
an interface, so that its values can only be manipulated by calling subroutines that have access to
the missing information. The concrete representation of the type is hidden from its users. A data
type whose representation is visible is called transparent.
Typical examples of opaque data types include handles for resources provided by
an operating system to application software. For example, the POSIX standard for threads
defines an application programming interface based on a number of opaque types that
represent threads or synchronization primitives like mutexes or condition variables.
An opaque pointer is a special case of an opaque data type, a data type that is declared to be
a pointer to a record or data structure of some unspecified data type. For example, the standard
library that forms part of the specification of the C programming language provides functions
for file input and output that return or take values of type "pointer toFILE" that represent file
streams (see C file input/output), but the concrete implementation of the type FILE is not
specified.
10. In some protocols, handles are passed from a server to the client. The client passes the
handle back to the server at some later time. Handles are never inspected by clients; they are
obtained and submitted. That is, handles are opaque. The xdr_opaque() primitive is used for
describing fixed-sized opaque bytes.
bool_t
xdr_opaque(xdrs, p, len)
XDR *xdrs;
char *p;
u_int len;
The parameter p is the location of the bytes, len is the number of bytes in the opaque object.
By definition, the actual data contained in the opaque object is not machine portable.In the
SunOS/SVR4 system is another routine for manipulating opaque data. This routine,
the xdr_netobj, sends counted opaque data, much like xdr_opaque(). The following code example
illustrates the syntax of xdr_netobj().
struct netobj {
u_int n_len;
char *n_bytes;
};
typedef struct netobj netobj;
bool_t
xdr_netobj(xdrs, np)
XDR *xdrs;
struct netobj *np;
The xdr_netobj() routine is a filter primitive that translates between variable-length opaque data
and its external representation. The parameter np is the address of the netobj structure containing
both a length and a pointer to the opaque data. The length may be no more
than MAX_NETOBJ_SZ bytes. This routine returns TRUE if it succeeds, FALSE otherwise.
B. What are the major advantages and disadvantages of using a port mapper instead of
well known ports?
Port mapping / Port Mapping is a name given to the combined technique of
1. translating the address or port number of a packet to a new destination
2. possibly accepting such packet(s) in a packet filter (firewall)
11. 3. forwarding the packet according to the routing table.
The destination may be a predetermined network port (assuming protocols like TCP and UDP,
though the process is not limited to these) on a host within a NAT-masqueraded, typically private
network, based on the port number on which it was received at the gateway from the originating
host.
The technique is used to permit communications by external hosts with services provided
within a private local area network.
Advantages:
Port mapping / Port Mapping basically allows an outside computer to connect to a computer
in a private local area network. Some commonly done port forwarding includes forwarding port 21
for FTP access, and forwarding port 80 for web servers. To achieve such results, operating
systems like the Mac OS X and the BSD (Berkeley Software Distribution) will use the pre-installed
in the kernel, ipfirewall (ipfw), to conduct port forwarding. Linux on the other hand would add
iptables to do port forwarding.
Disadvantages:
There are a few downsides or precautions to take with port forwarding / Port Mapping.
Only one port can be used at a time by one machine.
Port forwarding also allows any machine in the world to connect to the forwarded port at will, and
thus making the network slightly insecure.
The port forwarding technology itself is built in a way so that the destination machine will see the
incoming packets as coming from the router rather than the original machine sending out the
packets.
Q5. A. Compare DEC RPC to ONCRPC. How do the two differ
Remote procedure call is a method of supporting the development of applications that require
processes on different systems to communicate and coordinate their activities. This article
pursues a comparison of three important RPC's, namely, Open Network Computing (ONC),
Distributed Computing Environment (DCE), and the ISO specification of a RPC.
A general discussion of the RPC model, and its implementation are followed by describing the
features and capabilities, like the model used, the mechanism of information transfer and call
semantics of the three RPC's. The implementation of ONC and DEC are discussed. In a normal
procedure the call takes place between the procedures of a single process in the same memory
12. space on a single system, RPC takes place between a client and a server which are two different
systems connected to a network. An important feature discussed while describing the RPC model
is that of data representation.
The client stub, creates a message packet to be sent to the server by converting the input
arguments from the local data representation to a common data representation. On the server
side when the server stub is called by the server runtime, the input arguments are taken from the
message and converted from the common data representation to the local data representation.
ONC RPC: This was one of the first commercial implementations of RPC. Although a modified
implementation called the TI RPC is available, where the difference is in the latter being able to
use different Transport Layer Protocols, yet the success of the more widely used original RPC is
due to the wide use of NFS (Network file system, a client/server application that allows a user to
view and optionally store/update files on a remote computer). ONC supports At-most-once and
Idempotent call semantics. It also supports no-response and broadcast RPC. The type of
authentication supported are none (default), UNIX used ID/group ID and secure RPC.
Secure RPC uses DES (Data encryption Standard, a IBM product which uses more than 72
quadrillion or more possible encryption keys). RPC has reduced procedure declaration supporting
only one input parameter and one output parameter.
The RPC language compiler is called rpcgen which generates an include file, client stub,
server stub. The client stub produced by rpcgen is incomplete and in some cases needs the client
stub code to be generated by the developer. The server stub produced is nearly complete
B. Examine the specification for NFS version 2 and 3 what are the chief difference?
Does version 3 make any changes that are visible or important to a programmer?
The NFS protocol provides transparent remote access to shared file systems across
networks. The NFS protocol is designed to be machine, operating system, network architecture,
and security mechanism, and transport protocol independent. This independence is achieved
through the use of ONC Remote Procedure Call (RPC) primitives built on top of an eXternal Data
Representation (XDR). NFS protocol Version 2 is specified in the Network File System Protocol
Specification
Version 2 of the protocol (defined in RFC 1094, March 1989) originally operated only over
UDP. Its designers meant to keep the server side stateless, with locking (for example)
implemented outside of the core protocol. People involved in the creation of NF S version 2
include Russel Sandberg, Bob Lyon, Bill Joy, Steve Kleiman, and others. The decision to make
13. the file system stateless was a key decision, since it made recovery from server failures trivial (all
network clients would freeze up when a server crashed, but once the server repaired the file
system and restarted, all the state to retry each transaction was contained in each RPC, which
was retried by the client stub(s).) This design decision allowed UNIX applications (which could not
tolerate file server crashes) to ignore the problem
Version 3 details as follows:
support for 64-bit file sizes and offsets, to handle files larger than 2 gigabytes (GB); support
for asynchronous writes on the server, to improve write performance; additional file attributes in
many replies, to avoid the need to re-fetch them; a READDIRPLUS operation, to get file handles
and attributes along with file names when scanning a directory assorted other improvements.
At the time of introduction of Version 3, vendor support for TCP as a transport-layer protocol
began increasing. While several vendors had already added support for NFS Version 2 with TCP
as a transport, Sun Microsystems added support for TCP as a transport for NFS at the same time
it added support for Version 3. Using TCP as a transport made using NFS over a WAN more
feasible
Q6. A. Is it possible to make the server side of the dictionary program concurrent? Why or
why not?
Writing correct concurrent programs is harder than writing sequential ones. This is because the set of
potential risks and failure modes is larger - anything that can go wrong in a sequential program can
also go wrong in a concurrent one, and with concurrency comes additional hazards not present in
sequential programs such as race conditions, data races, deadlocks, missed signals, and livelock.
Testing concurrent programs is also harder than testing sequential ones. This is trivially true: tests for
concurrent programs are themselves concurrent programs. But it is also true for another reason: the
failure modes of concurrent programs are less predictable and repeatable than for sequential
programs. Failures in sequential programs are deterministic; if a sequential program fails with a given
set of inputs and initial state, it will fail every time. Failures in concurrent programs, on the other hand,
tend to be rare probabilistic events.
Because of this, reproducing failures in concurrent programs can be maddeningly difficult. Not only
might the failure be rare, and therefore not manifest itself frequently, but it might not occur at all in
certain platform configurations, so that bug that happens daily at your customer's site might never
happen at all in your test lab. Further, attempts to debug or monitor the program can introduce timing
or synchronization artifacts that prevents the bug from appearing at all. As in Heisenberg's uncertainty
principle, observing the state of the system may in fact change it.
14. B. Under what condition will read from a terminal return the value 0?
Any subsequent read from the terminal device shall return the value of zero, indicating end-of-
file. Thus, processes that read a terminal file and test for end-of-file can terminate
appropriately after a disconnect. If the EIO condition as specified in read() also exists, it is
unspecified whether on EOF condition or [EIO] is returned
C. If you had a choice debugging deadlock problem or a livelock Problem, which would
you choose? Why ? How would you proceed?