The document provides information about TELNET, SSH, and other protocols. It discusses:
1) What TELNET is, how it works, and how to check if it is enabled on different operating systems like Windows and Linux. It also covers how TELNET sessions work and the Network Virtual Terminal.
2) The history and development of SSH, how it works, its features like authentication, encryption, port forwarding etc. It also discusses the SSH protocol architecture and packet format.
3) Basic information about Network Information System (NIS) and Common Unix Printing System (CUPS), including their components and how they work.
TELNET is a TCP/IP protocol that allows users to connect to remote systems and access services as if their local terminal was connected directly to the remote system. It enables users to log in remotely using their username and password. TELNET uses control characters and option negotiation to translate between the local character set and the character set of the remote system, allowing the connection to function transparently. Common options negotiated are terminal type, echo, and line mode. This document provides details on how TELNET establishes and manages remote connections.
Overview of the TELNET protocol.
TELNET is a protocol providing platform independent, bi-directional byte-oriented communication between hosts (unlike rlogin which is Unix based).
Most often TELNET is used for remote login to hosts on the Internet.
TELNET is basically a TCP connection with interspersed TELNET control information.
TELNET may use option negotiation for providing additional services such as character echoing back to the sender.
TELNET does not provide any authentication and therefore should not be used in unsecure environments anymore. SSH (Secure SHell) should be used instead.
TELNET is a standard TCP/IP protocol that allows a user to access resources on a remote host from their local computer. It works by having a TELNET client program establish a TCP connection to a TELNET server on the destination system, allowing the client to send keystrokes and receive output character-by-character. While it was commonly used to administer network devices, TELNET has disadvantages like lack of graphics, security issues, and mouse support. However, it remains useful for configuring some network devices, participating in online communities that value its retro interface, and recreational uses.
Telnet is a network protocol used to provide bidirectional interactive text communication over a virtual terminal connection using TCP. It allows users to connect to remote hosts and access operating system command line interfaces. While once commonly used, telnet is now less favored for security reasons, replaced by more secure protocols like SSH for remote access. Most network equipment and operating systems still support a telnet service for remote configuration via telnet clients available on many platforms.
Telnet and SSH configuration on ubuntu and windows. this presentation show how we can configure telnet and ssh on windows and linux and what additional software we will have to required.
HTTP is the application-layer protocol for transmitting hypertext documents across the internet. It works by establishing a TCP connection between an HTTP client, like a web browser, and an HTTP server. The client sends a request to the server using methods like GET or POST. The server responds with a status code and the requested resource. HTTP is stateless, meaning each request is independent and servers do not remember past client interactions. Cookies and caching are techniques used to maintain some state and improve performance.
TELNET is a TCP/IP protocol that allows users to connect to remote systems and access services as if their local terminal was connected directly to the remote system. It enables users to log in remotely using their username and password. TELNET uses control characters and option negotiation to translate between the local character set and the character set of the remote system, allowing the connection to function transparently. Common options negotiated are terminal type, echo, and line mode. This document provides details on how TELNET establishes and manages remote connections.
Overview of the TELNET protocol.
TELNET is a protocol providing platform independent, bi-directional byte-oriented communication between hosts (unlike rlogin which is Unix based).
Most often TELNET is used for remote login to hosts on the Internet.
TELNET is basically a TCP connection with interspersed TELNET control information.
TELNET may use option negotiation for providing additional services such as character echoing back to the sender.
TELNET does not provide any authentication and therefore should not be used in unsecure environments anymore. SSH (Secure SHell) should be used instead.
TELNET is a standard TCP/IP protocol that allows a user to access resources on a remote host from their local computer. It works by having a TELNET client program establish a TCP connection to a TELNET server on the destination system, allowing the client to send keystrokes and receive output character-by-character. While it was commonly used to administer network devices, TELNET has disadvantages like lack of graphics, security issues, and mouse support. However, it remains useful for configuring some network devices, participating in online communities that value its retro interface, and recreational uses.
Telnet is a network protocol used to provide bidirectional interactive text communication over a virtual terminal connection using TCP. It allows users to connect to remote hosts and access operating system command line interfaces. While once commonly used, telnet is now less favored for security reasons, replaced by more secure protocols like SSH for remote access. Most network equipment and operating systems still support a telnet service for remote configuration via telnet clients available on many platforms.
Telnet and SSH configuration on ubuntu and windows. this presentation show how we can configure telnet and ssh on windows and linux and what additional software we will have to required.
HTTP is the application-layer protocol for transmitting hypertext documents across the internet. It works by establishing a TCP connection between an HTTP client, like a web browser, and an HTTP server. The client sends a request to the server using methods like GET or POST. The server responds with a status code and the requested resource. HTTP is stateless, meaning each request is independent and servers do not remember past client interactions. Cookies and caching are techniques used to maintain some state and improve performance.
SMTP (Simple Mail Transfer Protocol) is an Internet standard protocol for electronic mail transmission. It was first defined in 1982 and became widely used in the early 1980s as a complement to UUCP mail. SMTP uses a client-server model where the client initiates a connection and sends messages to the server, which then acknowledges receipt. It allows messages to be transferred between machines that are intermittently connected. Common SMTP commands include HELO, MAIL FROM, RCPT TO, DATA, QUIT, and RSET. SMTP can be secured using SSL/TLS to encrypt the communication channel. The latest developments include supporting real-time dynamic content in emails and internationalized email addresses encoded in UTF-8.
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.
Routing is the process of selecting a path for traffic in a network or between or across multiple networks. this slide helps to describe routing protocols and their various aspects.
HTTP is a request-response protocol for transferring data over the internet. It was introduced by Tim Berners-Lee at CERN. The client submits an HTTP request to the server, which responds with status information and requested content. HTTP uses TCP for network connectivity and relies on DNS to connect clients to servers. HTTP 1.0 defined GET, POST, and HEAD methods, while HTTP 1.1 added PUT, DELETE, TRACE, OPTIONS, and CONNECT. Persistent connections allow multiple requests/responses over a single TCP connection, improving efficiency versus non-persistent connections requiring separate TCP for each transaction.
HTTPS is a protocol that combines HTTP with SSL/TLS encryption to provide secure communication between a client and server. It encrypts data sent between a browser and website using a public/private key system. When a client requests an HTTPS connection, the website sends its SSL certificate containing a public key. This begins the SSL handshake where shared secrets are generated to uniquely encrypt the connection. HTTPS is important for securing sensitive communications and establishing trust, as it is used widely on banking, payment, shopping and email sites.
Reference models in Networks: OSI & TCP/IPMukesh Chinta
The document discusses reference models and the OSI reference model. It provides details on:
- The need for a reference model to standardize network components and layer functions to promote interoperability.
- The OSI reference model, approved in 1984, which divides communication problems into seven layers to aid in network interconnection.
- Each of the seven layers of the OSI model, describing their functions and responsibilities for moving data through the network.
The document discusses transport layer protocols TCP and UDP. It provides an overview of process-to-process communication using transport layer protocols. It describes the roles, services, requirements, addressing, encapsulation, multiplexing, and error control functions of the transport layer. It specifically examines TCP and UDP, comparing their connection-oriented and connectionless services, typical applications, and segment/datagram formats.
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.
Transport Layer Security (TLS) is the successor to the Secure Sockets Layer (SSL) protocol. TLS ensures privacy and security between communicating applications and users on the internet by preventing eavesdropping, tampering, and message forgery. It works by having the client and server negotiate a cipher suite and protocol version to use to securely transmit encrypted messages. This establishes a secure channel over an unsecured network like the internet to provide confidentiality, integrity, and authentication of communications.
The document discusses network models including the OSI model and TCP/IP model. It describes the seven layers of the OSI model and the functions of each layer. It also discusses the four layers of the TCP/IP model and compares the two models, noting they are similar in concept but differ in number of layers and how protocols fit within each model.
Unicasting , Broadcasting And Multicasting Newtechbed
This document summarizes three different types of network transmission methods: unicasting, multicasting, and broadcasting. Unicasting involves sending messages to a single destination host and requires a direct connection between client and server. Multicasting allows sending of data to multiple clients simultaneously by registering interest in the data stream. Broadcasting sends information from one source to all connected sources on a network segment.
This document provides an overview of routing concepts and protocols. It discusses the basic components of routing including algorithms, databases, and protocols. It describes different routing algorithm types such as static, distance vector, and link state. Specific routing protocols covered include RIP, OSPF, and BGP. It also discusses routing within autonomous systems and between autonomous systems on the internet.
This document discusses different types of routing in computer networks: unicast, broadcast, and multicast. It focuses on multicast routing and describes several multicast routing protocols, including distance vector multicast routing protocol (DVMRP) which uses flooding, reverse path forwarding (RPF), reverse path broadcasting (RPB), and reverse path multicasting (RPM). It also discusses protocol independent multicast (PIM) which has two modes: dense mode PIM uses source-based trees while sparse mode PIM uses group-shared trees with a rendezvous point.
This document discusses various application layer protocols. It begins with an agenda that lists OSI models, encapsulation processes, application protocol design, and specific protocols including HTTP, DNS, FTP, Telnet, DHCP, and SMTP. For each protocol, it provides details on how the protocol functions, message formats, and roles of clients and servers. The document is intended to describe key application layer protocols and their basic operations.
Telnet is a protocol that allows administrators to remotely access and manage devices, but it transmits usernames and passwords in clear text, posing a security risk. SSH is a more secure replacement for Telnet, as it encrypts all transmitted data using public key cryptography. Both protocols require a client and server, with Telnet using port 23 and SSH typically using port 22.
This document discusses subnetting and provides examples. It describes subnetting as breaking up a large network into smaller subnets. Subnetting allows creating multiple networks from a single address block and maximizes addressing efficiency. The document then provides examples of subnetting a network using CIDR notation and calculating the number of subnets, hosts per subnet, valid IP ranges, and broadcast addresses. It also discusses an example of optimally subnetting the IP addresses needed across different departments within a university based on their host requirements.
Link-state routing protocols use Dijkstra's algorithm to calculate the shortest path to all destinations based on a link-state database containing the full network topology. Each router runs the same algorithm locally to determine the optimal path. Key aspects include link-state advertisements to share connectivity information, the topological database to store network maps, and shortest path first calculations to derive routes. Common link-state protocols are OSPF and IS-IS. They provide fast convergence and scalability but require more resources than distance-vector protocols.
Remote login allows users to access their work computers from any internet-enabled device. It requires software on both the host computer and the remote computer, an internet connection, and secure desktop sharing. Common methods for remote login include SSH, PuTTY, VNC, and Telnet. SSH provides encrypted connections and is commonly used on Linux/Unix systems, while PuTTY is a Windows terminal emulator that can be used to connect via SSH, Telnet, or RDP. VNC allows controlling another computer's desktop remotely. Telnet provides unencrypted remote terminal access connections but is less secure than SSH or RDP.
This document discusses several remote login protocols:
1. TELNET is the standard Internet protocol for remote login that allows users to connect to accounts on remote machines. It has disadvantages like inefficiency from processing each keystroke multiple times as it travels across networks.
2. Secure Shell (SSH) is a popular alternative to TELNET that provides secure encrypted communications and can perform additional data transfers over the same connection.
3. Other remote login protocols discussed include rlogin for BSD UNIX systems, Virtual Network Computing (VNC) for remote desktop access across platforms, and Remote Desktop Protocol (RDP) defined by Microsoft.
SMTP (Simple Mail Transfer Protocol) is an Internet standard protocol for electronic mail transmission. It was first defined in 1982 and became widely used in the early 1980s as a complement to UUCP mail. SMTP uses a client-server model where the client initiates a connection and sends messages to the server, which then acknowledges receipt. It allows messages to be transferred between machines that are intermittently connected. Common SMTP commands include HELO, MAIL FROM, RCPT TO, DATA, QUIT, and RSET. SMTP can be secured using SSL/TLS to encrypt the communication channel. The latest developments include supporting real-time dynamic content in emails and internationalized email addresses encoded in UTF-8.
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.
Routing is the process of selecting a path for traffic in a network or between or across multiple networks. this slide helps to describe routing protocols and their various aspects.
HTTP is a request-response protocol for transferring data over the internet. It was introduced by Tim Berners-Lee at CERN. The client submits an HTTP request to the server, which responds with status information and requested content. HTTP uses TCP for network connectivity and relies on DNS to connect clients to servers. HTTP 1.0 defined GET, POST, and HEAD methods, while HTTP 1.1 added PUT, DELETE, TRACE, OPTIONS, and CONNECT. Persistent connections allow multiple requests/responses over a single TCP connection, improving efficiency versus non-persistent connections requiring separate TCP for each transaction.
HTTPS is a protocol that combines HTTP with SSL/TLS encryption to provide secure communication between a client and server. It encrypts data sent between a browser and website using a public/private key system. When a client requests an HTTPS connection, the website sends its SSL certificate containing a public key. This begins the SSL handshake where shared secrets are generated to uniquely encrypt the connection. HTTPS is important for securing sensitive communications and establishing trust, as it is used widely on banking, payment, shopping and email sites.
Reference models in Networks: OSI & TCP/IPMukesh Chinta
The document discusses reference models and the OSI reference model. It provides details on:
- The need for a reference model to standardize network components and layer functions to promote interoperability.
- The OSI reference model, approved in 1984, which divides communication problems into seven layers to aid in network interconnection.
- Each of the seven layers of the OSI model, describing their functions and responsibilities for moving data through the network.
The document discusses transport layer protocols TCP and UDP. It provides an overview of process-to-process communication using transport layer protocols. It describes the roles, services, requirements, addressing, encapsulation, multiplexing, and error control functions of the transport layer. It specifically examines TCP and UDP, comparing their connection-oriented and connectionless services, typical applications, and segment/datagram formats.
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.
Transport Layer Security (TLS) is the successor to the Secure Sockets Layer (SSL) protocol. TLS ensures privacy and security between communicating applications and users on the internet by preventing eavesdropping, tampering, and message forgery. It works by having the client and server negotiate a cipher suite and protocol version to use to securely transmit encrypted messages. This establishes a secure channel over an unsecured network like the internet to provide confidentiality, integrity, and authentication of communications.
The document discusses network models including the OSI model and TCP/IP model. It describes the seven layers of the OSI model and the functions of each layer. It also discusses the four layers of the TCP/IP model and compares the two models, noting they are similar in concept but differ in number of layers and how protocols fit within each model.
Unicasting , Broadcasting And Multicasting Newtechbed
This document summarizes three different types of network transmission methods: unicasting, multicasting, and broadcasting. Unicasting involves sending messages to a single destination host and requires a direct connection between client and server. Multicasting allows sending of data to multiple clients simultaneously by registering interest in the data stream. Broadcasting sends information from one source to all connected sources on a network segment.
This document provides an overview of routing concepts and protocols. It discusses the basic components of routing including algorithms, databases, and protocols. It describes different routing algorithm types such as static, distance vector, and link state. Specific routing protocols covered include RIP, OSPF, and BGP. It also discusses routing within autonomous systems and between autonomous systems on the internet.
This document discusses different types of routing in computer networks: unicast, broadcast, and multicast. It focuses on multicast routing and describes several multicast routing protocols, including distance vector multicast routing protocol (DVMRP) which uses flooding, reverse path forwarding (RPF), reverse path broadcasting (RPB), and reverse path multicasting (RPM). It also discusses protocol independent multicast (PIM) which has two modes: dense mode PIM uses source-based trees while sparse mode PIM uses group-shared trees with a rendezvous point.
This document discusses various application layer protocols. It begins with an agenda that lists OSI models, encapsulation processes, application protocol design, and specific protocols including HTTP, DNS, FTP, Telnet, DHCP, and SMTP. For each protocol, it provides details on how the protocol functions, message formats, and roles of clients and servers. The document is intended to describe key application layer protocols and their basic operations.
Telnet is a protocol that allows administrators to remotely access and manage devices, but it transmits usernames and passwords in clear text, posing a security risk. SSH is a more secure replacement for Telnet, as it encrypts all transmitted data using public key cryptography. Both protocols require a client and server, with Telnet using port 23 and SSH typically using port 22.
This document discusses subnetting and provides examples. It describes subnetting as breaking up a large network into smaller subnets. Subnetting allows creating multiple networks from a single address block and maximizes addressing efficiency. The document then provides examples of subnetting a network using CIDR notation and calculating the number of subnets, hosts per subnet, valid IP ranges, and broadcast addresses. It also discusses an example of optimally subnetting the IP addresses needed across different departments within a university based on their host requirements.
Link-state routing protocols use Dijkstra's algorithm to calculate the shortest path to all destinations based on a link-state database containing the full network topology. Each router runs the same algorithm locally to determine the optimal path. Key aspects include link-state advertisements to share connectivity information, the topological database to store network maps, and shortest path first calculations to derive routes. Common link-state protocols are OSPF and IS-IS. They provide fast convergence and scalability but require more resources than distance-vector protocols.
Remote login allows users to access their work computers from any internet-enabled device. It requires software on both the host computer and the remote computer, an internet connection, and secure desktop sharing. Common methods for remote login include SSH, PuTTY, VNC, and Telnet. SSH provides encrypted connections and is commonly used on Linux/Unix systems, while PuTTY is a Windows terminal emulator that can be used to connect via SSH, Telnet, or RDP. VNC allows controlling another computer's desktop remotely. Telnet provides unencrypted remote terminal access connections but is less secure than SSH or RDP.
This document discusses several remote login protocols:
1. TELNET is the standard Internet protocol for remote login that allows users to connect to accounts on remote machines. It has disadvantages like inefficiency from processing each keystroke multiple times as it travels across networks.
2. Secure Shell (SSH) is a popular alternative to TELNET that provides secure encrypted communications and can perform additional data transfers over the same connection.
3. Other remote login protocols discussed include rlogin for BSD UNIX systems, Virtual Network Computing (VNC) for remote desktop access across platforms, and Remote Desktop Protocol (RDP) defined by Microsoft.
Rlogin, Telnet, and SSH are remote access protocols. Rlogin and Telnet transmit information in plaintext, posing security risks, while SSH uses cryptography to secure connections. SSH was developed in 1995 as a more secure replacement for insecure remote shells like Rlogin and Telnet. SSH provides secure login, file transfer, and process execution between computers using encryption techniques like public-key authentication and symmetric encryption.
Telnet is an early network protocol that allows text-based access to remote systems but lacks security features. It works at the application layer and provides bidirectional interactive text communication through a virtual terminal connection. SSH was developed as a secure replacement for Telnet, supporting encryption, authentication, and integrity to prevent eavesdropping and spoofing. It uses public/private key cryptography to securely transmit data and authenticate systems. While still used occasionally, SSH is now generally preferred over Telnet for remote access due to its enhanced security.
TELNET is an unsecure protocol that enables remote terminal connections by establishing virtual terminal sessions. It uses cleartext for authentication, allowing passwords to be easily sniffed. SSH was created as a secure replacement for TELNET and other insecure protocols, providing encryption, integrity checks, and authentication to prevent sniffing of passwords and data on untrusted networks.
Application layer and protocols of application layerTahmina Shopna
The document summarizes several key application layer protocols: Telnet allows remote access to servers by emulating a terminal. FTP is used to transfer files between machines. TFTP is a simplified version of FTP with no security. NFS enables accessing files over a network like local storage. SMTP is the standard for email services. LPD/LPR is for remote printing. X Window provides GUI functionality over networks. SNMP allows monitoring of network devices. DNS translates human-readable names to IP addresses. DHCP automatically assigns IP addresses to devices on a network.
The document discusses Secure Shell (SSH), which provides secure remote login and file transfer capabilities over insecure networks. It describes the SSH-1 and SSH-2 protocols, including their key exchanges, authentication methods, and components. Vulnerabilities are outlined for each version. SSH tools for Linux and Windows are also mentioned.
SSH (Secure Shell) is a network protocol that allows secure data exchange and remote access over an unsecured network. It uses public-key cryptography to authenticate the remote host and encrypt the data transmission, providing confidentiality and integrity. SSH is commonly used for remote login, command execution, and file transfer. An SSH server listens on port 22 by default to accept connections from SSH clients, which are typically used to log into remote machines and execute commands securely.
Standard Client / Server Protocols: Worldwide- web and HTTP,FTP, Electronic mail, Telnet, Secured Shell, Domain name system. Application layer: DNS: Name space – domain name space – distribution of name space Electronic mail Architecture – FILE transfer: FTP WWW and HTTP: Architecture – web documents – HTTP Network Security: Introduction - definitions – two categories - symmetric key cryptography – traditional ciphers – asymmetric key cryptography
The document summarizes various application layer protocols including Telnet, FTP, TFTP, NFS, SMTP, LPD, X-Window, SNMP, DNS, and HTTP. It discusses what each protocol is used for and some key details like typical port numbers. The application layer is presented as being at the top of the OSI model and providing services to users through interaction and file transfers between senders and receivers using these defined protocols.
The document discusses several methods for remote login and remote access to computers including telnet, remote shell, secure shell (SSH), remote administrator (Radmin), and WinSCP. Telnet, remote shell, and Radmin are not secure as they do not encrypt network traffic while SSH and WinSCP provide encryption and security. SSH is widely used on Linux and Unix systems to securely access shell accounts remotely over an insecure network like the internet. WinSCP is an open source SFTP and FTP client that uses SSH to securely transfer files between computers.
This document provides an overview of various application layer protocols including HTTP, HTTPS, SMTP, POP3, FTP, SFTP, SCP, Telnet, and SSH. It describes each protocol, including what they are used for and how they differ. Some key points:
- HTTP and HTTPS are used to access data on the world wide web, with HTTPS providing encryption for secure transactions.
- SMTP and POP3 are used for email, with SMTP sending messages between servers and POP3 allowing users to receive messages from their inbox.
- FTP and SFTP are used for file transfer, with SFTP encrypting data for security unlike regular FTP. SCP also provides secure file transfer.
- Tel
A protocol defines common rules for network communication between devices. Some common protocols include HTTP, HTTPS, FTP, SMTP, and Telnet. HTTP is used for web browsing and transferring HTML files. HTTPS provides secure communication over HTTP using encryption. FTP transfers files between servers and clients. SMTP sends and receives email. Telnet allows interactive text-based sessions between devices. Each protocol has a specific purpose and set of rules for data exchange and transmission.
Telnet is a network protocol used to provide bidirectional interactive text communication over TCP. It allows connecting a client (with display and keyboard) to a remote command line interface. Telnet uses ASCII encoding and negotiates options to support advanced functions. While it provided remote access historically, security issues have led to decreased use for that purpose in favor of SSH.
Remote login allows users to access their work computers from any internet-enabled device. It requires the host computer to be running desktop sharing software and connected to both the internet and a secure network. When a remote login request is made, the desktop sharing software establishes a session between the two computers and exchanges data through a secure channel, allowing the user to access the host computer remotely. Common methods for remote login include SSH for Linux/Unix systems and Telnet, which transforms keystrokes into standard characters that travel over the internet to grant remote terminal access to another system.
Telnet is a protocol that enables one computer to connect to another computer remotely. It uses a client-server model, with the local computer running the telnet client and the remote computer running the telnet server. Telnet allows the user to access and interact with the remote computer through their local computer. Commands are prefixed with IAC and can be sent in one of three modes: default, character, or line mode. Telnet is used for remote login while FTP is used for file transfer between systems.
The document summarizes several key application layer protocols in computer networks. It discusses the Domain Name System (DNS) which maps domain names to IP addresses. It also describes remote login protocols like Telnet and SSH, electronic mail protocols like SMTP, file transfer protocols like FTP and SCP, and the Hypertext Transfer Protocol (HTTP) which underlies the World Wide Web. It provides an overview of Voice over IP (VoIP) technology and signaling protocols used for call setup and management in IP telephony systems.
This document provides an overview of common network services and the ports they use. It describes services like DNS (port 53), DHCP (ports 67, 68), HTTP (port 80), HTTPS (port 443), FTP (port 21), SMTP (port 25), SMB (ports 445, 139), RDP (port 3389), and SQL (port 3306). Each service is defined along with the typical function it provides over a computer network and the client-server architecture most often used to deliver that service.
This document discusses network protocols. It begins by defining what a protocol is and provides some common examples used at different layers, such as TCP, UDP, IP, and HTTP. It then explains that protocols break large processes into smaller tasks and functions that must cooperate across network levels. Protocols are created according to industry standards. The document categorizes protocols for communication, network management, and security. It provides examples for each category and concludes with descriptions of some frequently used protocols like HTTP, SSH, and SMS.
“An Outlook of the Ongoing and Future Relationship between Blockchain Technologies and Process-aware Information Systems.” Invited talk at the joint workshop on Blockchain for Information Systems (BC4IS) and Blockchain for Trusted Data Sharing (B4TDS), co-located with with the 36th International Conference on Advanced Information Systems Engineering (CAiSE), 3 June 2024, Limassol, Cyprus.
Building RAG with self-deployed Milvus vector database and Snowpark Container...Zilliz
This talk will give hands-on advice on building RAG applications with an open-source Milvus database deployed as a docker container. We will also introduce the integration of Milvus with Snowpark Container Services.
Generative AI Deep Dive: Advancing from Proof of Concept to ProductionAggregage
Join Maher Hanafi, VP of Engineering at Betterworks, in this new session where he'll share a practical framework to transform Gen AI prototypes into impactful products! He'll delve into the complexities of data collection and management, model selection and optimization, and ensuring security, scalability, and responsible use.
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024Albert Hoitingh
In this session I delve into the encryption technology used in Microsoft 365 and Microsoft Purview. Including the concepts of Customer Key and Double Key Encryption.
20 Comprehensive Checklist of Designing and Developing a WebsitePixlogix Infotech
Dive into the world of Website Designing and Developing with Pixlogix! Looking to create a stunning online presence? Look no further! Our comprehensive checklist covers everything you need to know to craft a website that stands out. From user-friendly design to seamless functionality, we've got you covered. Don't miss out on this invaluable resource! Check out our checklist now at Pixlogix and start your journey towards a captivating online presence today.
GraphSummit Singapore | The Future of Agility: Supercharging Digital Transfor...Neo4j
Leonard Jayamohan, Partner & Generative AI Lead, Deloitte
This keynote will reveal how Deloitte leverages Neo4j’s graph power for groundbreaking digital twin solutions, achieving a staggering 100x performance boost. Discover the essential role knowledge graphs play in successful generative AI implementations. Plus, get an exclusive look at an innovative Neo4j + Generative AI solution Deloitte is developing in-house.
Full-RAG: A modern architecture for hyper-personalizationZilliz
Mike Del Balso, CEO & Co-Founder at Tecton, presents "Full RAG," a novel approach to AI recommendation systems, aiming to push beyond the limitations of traditional models through a deep integration of contextual insights and real-time data, leveraging the Retrieval-Augmented Generation architecture. This talk will outline Full RAG's potential to significantly enhance personalization, address engineering challenges such as data management and model training, and introduce data enrichment with reranking as a key solution. Attendees will gain crucial insights into the importance of hyperpersonalization in AI, the capabilities of Full RAG for advanced personalization, and strategies for managing complex data integrations for deploying cutting-edge AI solutions.
GraphSummit Singapore | The Art of the Possible with Graph - Q2 2024Neo4j
Neha Bajwa, Vice President of Product Marketing, Neo4j
Join us as we explore breakthrough innovations enabled by interconnected data and AI. Discover firsthand how organizations use relationships in data to uncover contextual insights and solve our most pressing challenges – from optimizing supply chains, detecting fraud, and improving customer experiences to accelerating drug discoveries.
Communications Mining Series - Zero to Hero - Session 1DianaGray10
This session provides introduction to UiPath Communication Mining, importance and platform overview. You will acquire a good understand of the phases in Communication Mining as we go over the platform with you. Topics covered:
• Communication Mining Overview
• Why is it important?
• How can it help today’s business and the benefits
• Phases in Communication Mining
• Demo on Platform overview
• Q/A
Cosa hanno in comune un mattoncino Lego e la backdoor XZ?Speck&Tech
ABSTRACT: A prima vista, un mattoncino Lego e la backdoor XZ potrebbero avere in comune il fatto di essere entrambi blocchi di costruzione, o dipendenze di progetti creativi e software. La realtà è che un mattoncino Lego e il caso della backdoor XZ hanno molto di più di tutto ciò in comune.
Partecipate alla presentazione per immergervi in una storia di interoperabilità, standard e formati aperti, per poi discutere del ruolo importante che i contributori hanno in una comunità open source sostenibile.
BIO: Sostenitrice del software libero e dei formati standard e aperti. È stata un membro attivo dei progetti Fedora e openSUSE e ha co-fondato l'Associazione LibreItalia dove è stata coinvolta in diversi eventi, migrazioni e formazione relativi a LibreOffice. In precedenza ha lavorato a migrazioni e corsi di formazione su LibreOffice per diverse amministrazioni pubbliche e privati. Da gennaio 2020 lavora in SUSE come Software Release Engineer per Uyuni e SUSE Manager e quando non segue la sua passione per i computer e per Geeko coltiva la sua curiosità per l'astronomia (da cui deriva il suo nickname deneb_alpha).
Enchancing adoption of Open Source Libraries. A case study on Albumentations.AIVladimir Iglovikov, Ph.D.
Presented by Vladimir Iglovikov:
- https://www.linkedin.com/in/iglovikov/
- https://x.com/viglovikov
- https://www.instagram.com/ternaus/
This presentation delves into the journey of Albumentations.ai, a highly successful open-source library for data augmentation.
Created out of a necessity for superior performance in Kaggle competitions, Albumentations has grown to become a widely used tool among data scientists and machine learning practitioners.
This case study covers various aspects, including:
People: The contributors and community that have supported Albumentations.
Metrics: The success indicators such as downloads, daily active users, GitHub stars, and financial contributions.
Challenges: The hurdles in monetizing open-source projects and measuring user engagement.
Development Practices: Best practices for creating, maintaining, and scaling open-source libraries, including code hygiene, CI/CD, and fast iteration.
Community Building: Strategies for making adoption easy, iterating quickly, and fostering a vibrant, engaged community.
Marketing: Both online and offline marketing tactics, focusing on real, impactful interactions and collaborations.
Mental Health: Maintaining balance and not feeling pressured by user demands.
Key insights include the importance of automation, making the adoption process seamless, and leveraging offline interactions for marketing. The presentation also emphasizes the need for continuous small improvements and building a friendly, inclusive community that contributes to the project's growth.
Vladimir Iglovikov brings his extensive experience as a Kaggle Grandmaster, ex-Staff ML Engineer at Lyft, sharing valuable lessons and practical advice for anyone looking to enhance the adoption of their open-source projects.
Explore more about Albumentations and join the community at:
GitHub: https://github.com/albumentations-team/albumentations
Website: https://albumentations.ai/
LinkedIn: https://www.linkedin.com/company/100504475
Twitter: https://x.com/albumentations
Sudheer Mechineni, Head of Application Frameworks, Standard Chartered Bank
Discover how Standard Chartered Bank harnessed the power of Neo4j to transform complex data access challenges into a dynamic, scalable graph database solution. This keynote will cover their journey from initial adoption to deploying a fully automated, enterprise-grade causal cluster, highlighting key strategies for modelling organisational changes and ensuring robust disaster recovery. Learn how these innovations have not only enhanced Standard Chartered Bank’s data infrastructure but also positioned them as pioneers in the banking sector’s adoption of graph technology.
For the full video of this presentation, please visit: https://www.edge-ai-vision.com/2024/06/building-and-scaling-ai-applications-with-the-nx-ai-manager-a-presentation-from-network-optix/
Robin van Emden, Senior Director of Data Science at Network Optix, presents the “Building and Scaling AI Applications with the Nx AI Manager,” tutorial at the May 2024 Embedded Vision Summit.
In this presentation, van Emden covers the basics of scaling edge AI solutions using the Nx tool kit. He emphasizes the process of developing AI models and deploying them globally. He also showcases the conversion of AI models and the creation of effective edge AI pipelines, with a focus on pre-processing, model conversion, selecting the appropriate inference engine for the target hardware and post-processing.
van Emden shows how Nx can simplify the developer’s life and facilitate a rapid transition from concept to production-ready applications.He provides valuable insights into developing scalable and efficient edge AI solutions, with a strong focus on practical implementation.
Essentials of Automations: The Art of Triggers and Actions in FMESafe Software
In this second installment of our Essentials of Automations webinar series, we’ll explore the landscape of triggers and actions, guiding you through the nuances of authoring and adapting workspaces for seamless automations. Gain an understanding of the full spectrum of triggers and actions available in FME, empowering you to enhance your workspaces for efficient automation.
We’ll kick things off by showcasing the most commonly used event-based triggers, introducing you to various automation workflows like manual triggers, schedules, directory watchers, and more. Plus, see how these elements play out in real scenarios.
Whether you’re tweaking your current setup or building from the ground up, this session will arm you with the tools and insights needed to transform your FME usage into a powerhouse of productivity. Join us to discover effective strategies that simplify complex processes, enhancing your productivity and transforming your data management practices with FME. Let’s turn complexity into clarity and make your workspaces work wonders!
Removing Uninteresting Bytes in Software FuzzingAftab Hussain
Imagine a world where software fuzzing, the process of mutating bytes in test seeds to uncover hidden and erroneous program behaviors, becomes faster and more effective. A lot depends on the initial seeds, which can significantly dictate the trajectory of a fuzzing campaign, particularly in terms of how long it takes to uncover interesting behaviour in your code. We introduce DIAR, a technique designed to speedup fuzzing campaigns by pinpointing and eliminating those uninteresting bytes in the seeds. Picture this: instead of wasting valuable resources on meaningless mutations in large, bloated seeds, DIAR removes the unnecessary bytes, streamlining the entire process.
In this work, we equipped AFL, a popular fuzzer, with DIAR and examined two critical Linux libraries -- Libxml's xmllint, a tool for parsing xml documents, and Binutil's readelf, an essential debugging and security analysis command-line tool used to display detailed information about ELF (Executable and Linkable Format). Our preliminary results show that AFL+DIAR does not only discover new paths more quickly but also achieves higher coverage overall. This work thus showcases how starting with lean and optimized seeds can lead to faster, more comprehensive fuzzing campaigns -- and DIAR helps you find such seeds.
- These are slides of the talk given at IEEE International Conference on Software Testing Verification and Validation Workshop, ICSTW 2022.
Threats to mobile devices are more prevalent and increasing in scope and complexity. Users of mobile devices desire to take full advantage of the features
available on those devices, but many of the features provide convenience and capability but sacrifice security. This best practices guide outlines steps the users can take to better protect personal devices and information.
3. What is TELNET?
Standard TCP/IP protocol that runs at application
layer of a network
The TELNET protocol provides a standardized
interface, through which a program on one host
(the TELNET client) may access the resources of
another host (the TELNET server) as though the
client were a local terminal connected to the server.
Protocol for Remote login
The TELNET client uses an ephemeral port
number while server uses port number 23 of TCP.
4. Checking TELNET?
Every major computer operating system,
including Unix, Linux, Mac OS and
Windows, has Telnet capabilities and may
even have Telnet built into them.
To find out, open the command box in your
system and enter the command: TELNET
HOST, with HOST being the name of the
remote host computer with which you would
like to connect.
5. Windows:
Telnet is in built in Windows but is turned off
In order to use it, it must be turned on first.
6. Red Hat / Fedora Linux
The configuration file for telnet is
/etc/xinetd.d/telnet.
To enable telnet server you need to open
this file and make sure disable = no read as
disable = yes
7. Exiting TELNET
Windows uses LOGOFF. It closes the
session on server as well as client.
In case the command doesn’t work, use
ABORT but only as your last resort.
8. Processes in TELNET:
Each Telnet command console session
consists of two processes:
1. Tlntsess.exe
2. Cmd.exe.
Tlntsess.exe is responsible for managing
the Telnet session.
Cmd.exe is the command interpreter, or
shell program, that runs commands,
programs, or scripts on the host.
9. How does TELNET work?
A user is logged in to the local system, and
invokes a TELNET program (the TELNET
client) by typing
telnet xxx.xxx.xxx
where xxx.xxx.xxx is either a host name or an IP
address.
The TELNET client is started on the local
machine That client establishes a TCP
connection with the TELNET server on the
destination system.
Once the connection has been established, the
client program accepts keystrokes from the
user and relays them, generally one character
at a time, to the TELNET server.
10. In general, a TELNET server is
implemented as a master server with some
number of slave servers.
The master server listens for service
requests from clients. When it hears one, it
spawns a slave server to handle that
specific request, while the master goes
back to listening for more requests.
11. The NVT!!
The biggest difficulty is the heterogeneity of
the terminals and operating systems that
must be supported.
All do not use the same control characters
for the same purposes.
To accommodate this heterogeneity,
Network Virtual Terminal (NVT) was
introduced.
Any user TELNETting in to a remote site is
deemed to be on an NVT, regardless of the
actual terminal type being used
12.
13.
14. User logs in
User sends key stokes to terminal driver.
Local OS accepts them but does not interpret.
Characters sent to TELNET client
TELNET client transforms them into NVT
characters and delivers them to local TCP/IP
stack
Commands or text in NVT form travel through
Internet.
Received by operating system on the remote
machine
Transferred to TELNET server.
TELNET server changes NVT characters into
corresponding characters readable by remote
machine.
Passed to operating system and application
programs via pseudo terminal.
15. NVT character set:
Is made up of 8 bits
Has two sets of characters:
1. for data
2. for control
16. Data characters:
Uses NVT ASCII
Seven lowest order bits are same as
US ASCII codes
Hisghets order bit is set to 0
Control characters:
Highest order bit is set to 1 and other
represent the binary code for the
control characters
17.
18. TELNET Command Structure
The communication between client and server is
handled with internal commands, which are not
accessible by users.
All internal TELNET commands consist of 2 or 3-byte
sequences, depending on the command type.
The Interpret As Command (IAC) character is followed
by a command code. If this command deals with option
negotiation, the command will have a third byte to show
the code for the referenced option.
19. Disadvantages of TELNET:
You cannot run GUI tools over a Telnet
connection
Telnet is a character-based communication
protocol. It is not designed to transmit cursor
movements or graphical user interface information.
Because of this, you can only run command line
programs, shell commands, scripts, and batch files
over a Telnet connection.
It is not a secure protocol.
21. THE NEED FOR SSH
•With the evolution of the internet, services such as file transfers,
remote logins, and remote command executions became possible.
•Existing implementations of protocols that supported these
services included FTP, RCP, TELNET, RLOGIN, and RSH.
•Problem existed with these protocols:
They lacked security ! (r-commands)
Possible for an intruder to intercept and read data.
•Telnet was especially risky:
Plaintext user name and password was easily intercepted
over the network.
•A new protocol was needed to fix these security problems.
22. HISTORY OF SSH
•Event & Result:
•1995 Finland University network compromised via a password-
sniffing attack.
•Tatu Ylönen, a researcher at the university develops the SSH1
product for himself to improve security.
•SSH1 quickly grew popular and its use increased:
•SSH1 released with a free license
• Ylönen founded a company (SSH Communications
Security/SCS).
• He submits the SSH-1 protocol to the IETF.
•Problems were discovered that were not fixable without losing
backwards compatibility.
•In 1996, a new version of the protocol was released:
•New Protocol named SSH 2.0 or SSH-2.
•It improved both security and features of SSH-1.
•Multiple shell sessions over a single SSH connection was made
possible and improved security with (D-H) key exchange.
•IETF formed the SECSH group to standardize the protocol and the
group submitted the protocol SSH-2 in 1997.
23. CONTINUATION OF HISTORY……
•SCS released SSH2, a s/w product based on the SSH-2 protocol, in
1998.
•It had restrictive licenses & hence had lesser usage.
•Till then use of SSH1 was still large as it had an unrestricted
license for users
•2000, SCS eased their restrictive licenses:
•Allowed several operating systems to implement them including
Linux, NetBSD, FreeBSD, and OpenBSD.
•OpenBSD developed OpenSSH, another SSH implementation
•Freely available under the OpenBSD license
•Presently used in several operating systems.
•In 2006, SSH-2 protocol became the proposed internet standard by
the IETF. Today, SSH is supported by several operating systems
including Linux, Mac, and Windows.
24. What is ssh ??
•SSH is both a program and a protocol:
•Allows users to securely log into another computer over an
insecure network, executes commands and transfers files
•Created as a replacement for TELNET, ftp, and rlogin, rsh, and
rcp.
• Uses TCP and provides authentication, confidentiality (both
data and command), integrity, authorization, data compression,
and with SSH-2,multiplexing .
•Has transparent client/server communication over encrypted
network connections
•Can be implemented on most Operating Systems Win, Mac,
Unix/Linux etc.
•What it’s Not ?
•It is not a shell / Command Interpreter in the sense of Unix
Bourne shell and C shell but provides a channel to run shell on a
remote computer.
25. SSH FEATURES
1. Authentication
Proof of identity of users and servers, typically password and
public key signature.
2. Privacy
Via strong standard encryption algorithms
3. Integrity
Cryptographic integrity checking via MD5 and SHA-1 keyed hash
algorithms
4. Authorization / Access
Server configurable access
5. Forwarding or Tunnelling
Encrypt other TCP/IP-based sessions
6. Data Compression
26. ADVANTAGES
•SSH is available on most platform
•Clients are available for many platforms (besides major Operating System –
OS/2, BeOS, Java, etc.)
•Free for noncommercial use
•The open source version has gone through many improvements with patches,
bug fixes, and addition of functionalities.
•lsh is the General Public License (GPL) version of SSH-2 – currently being
standardized by the IETF SECSH working group.
•SSH can multiplex services over the same connection
•One of the most powerful function of multiplexing is port forwarding or
tunneling
•SSH can securely tunnel insecure applications like POP3, SMTP, IMAP, and
CVS.
27. PROTECTION
Perhaps, the most important advantage of SSH is its
protection against packet spoofing, IP/host spoofing,
password sniffing, and eavesdropping.
•SSH uses user and host key rather than IP address.
SSH is less susceptible to packet spoofing and IP/host spoofing.
•SSH implements cryptography for both authentication and
communication.
Strong encryption make password sniffing and eavesdropping
virtually impossible.
28. DISADVANTAGES
•Only support known port number
•Dynamic port not supported
•Port Number can be exploited.
•SSH cannot fix all TCP’s problems since TCP run below SSH
•Can minimize attack types with authentication and security
•Network hijacking – SSH is vulnerable to DoS
•SSH cannot protect users from attack made through other protocols.
•E.g. NFS mounting can allow malicious access to root on
UNIX/LINUX systems
•SSH provides no protection against Trojan horses or viruses
29. SSH 2 PROTOCOL ARCHITECTURE
SSH is a proposed application layer protocol with four
components as shown in the diagram:
30. SSH-2 is separated into modules and consists of four components
three of which are protocols working together and one is SSH
Application
1.SSH Transport Layer Protocol (SSH-TRANS)
• server authentication, confidentiality, and integrity.
• runs over a TCP/IP connection or some other reliable
data stream.
2.SSH Authentication Protocol (SSH-AUTH)
• authenticates the client-side user to the server.
• runs over the transport layer protocol.
3.SSH Connection Protocol (SSH-CONN)
• multiplexes the encrypted tunnel into several logical
channels.
• runs over the user authentication protocol.
4. SSH Application
• After connection phase completion, it allows several
application programs to use the connection where
31. Port forwarding or tunneling
One of the services provided by SSH protocol is to provide port
forwarding. We can use the secured channels available in SSH to
access an application program such as TELNET that does not
provide security services.
32. •Port forwarding, also called tunneling, reroutes a TCP/IP connection to
pass through an SSH connection.
• client side splicing is called local port forwarding (-L option) i.e.
connections from the SSH client are forwarded via the SSH server, then to
a destination server.
•server side splicing is called remote port forwarding (-R option) i.e.
connections from the SSH server are forwarded via the SSH client, then to
a destination server
•It is called tunneling because it creates a tunnel through which the
messages belonging to other protocol can travel.
•With the help of this we can change a direct, but insecure, connection
between the TELNET client and TELNET server
•It is not completely transparent, occurs at the application level, not the
network .
•Connect to servers such as SMTP, IMAP, POP, and LDAP across a
firewall that does not allow direct access while encrypting those
33. Ssh packet format
Length: 4-byte field defines length of packet including the type
,data and CRC fields.
Padding: 1-8 bytes field, its added to the packet to make the attack
on security provision more difficult.
Type: 1 byte field defines the type of packet used by SSH protocols.
Data: This is of variable length. Its length can be found by deducting
5 bytes from the value of the length field.
CRC: The cyclic redundancy check field is used for error detection.
37. NIS is a network naming and administration
system for smaller networks that was
developed by Sun Microsystems.
It was initially called Yellow Pages , in
reference to the famous US directory.
Sun changed the name of its system to NIS,
though all the commands and functions still
start with “yp”.
NIS+ is a later version that provides
additional security and other facilities.
38. Using NIS, each host client or server
computer in the system has knowledge
about the entire system.
A user at any host can get access to files or
applications on any host in the network with
a single user identification and password.
A NIS/YP system maintains and distributes
a central directory of user and group
information, hostnames, e-mail aliases and
other text-based tables of information in a
computer network.
39. Types of hosts:
There are three types of hosts in an NIS:
1. NIS master server
2. NIS slave servers
3. NIS clients
40. NIS Master Server:
A central repository for host configuration
information and maintains the authoritative
copy of the files used by all of the NIS clients.
The passwd, group, and other various files used
by NIS clients are stored on the master server.
41. NIS slave servers
NIS slave servers maintain copies of
the NIS master's data files in order to
provide redundancy.
Slave servers also help to balance the load
of the master server as NIS clients always
attach to the NIS server which responds
first.
42. NIS clients
NIS clients authenticate against
the NIS server during log on.
44. BASIC INFORMATION
Original author : Michael Sweet (Easy
Software Products)
Developer : Apple Inc.
Initial release : June 9, 1999
Stable release : 2.1 / August 31, 2015[1]
Preview release : 2.1RC1
Written in : C
Operating system : Unix-like, Windows
Type :Print server
License : GNU General Public
License,
GNU Lesser General Public
License
45. introduction
CUPS Common Unix Printing System) is a modular
printing system for Unix-like computer operating systems
which allows a computer to act as a print server. A
computer running CUPS is a host that can accept print
jobs from client computers, process them, and send
them to the appropriate printer.
CUPS consists of a print spooler and scheduler, a filter
system that converts the print data to a format that the
printer will understand, and a backend system that
sends this data to the print device.
46. CUPS uses the Internet Printing Protocol
(IPP) as the basis for managing print jobs and
queues.
There are a number of user interfaces for
different platforms that can configure CUPS,
and it has a built-in web-based interface.
CUPS is free software, provided under the
GNU General Public License and GNU
Lesser General Public License, Version 2.
47. working
•CUPS provides a mechanism that allows print jobs to be
sent to printers in a standard fashion.
•The print-data goes to a scheduler which sends jobs to
a filter system that converts the print job into a format the
printer will understand.
•The filter system then passes the data on to a
backend—a special filter that sends print data to a device
or network connection.
•The system makes extensive use of PostScript and
rasterization of data to convert the data into a format
suitable for the destination printer.
50. SCHEDULER :
•The CUPS scheduler implements Internet
Printing Protocol (IPP) over HTTP/1.1.
•The scheduler provides a web-based
interface for managing print jobs, the
configuration of the server, and for
documentation about CUPS itself.
51. FILTER SYSTEM:
•CUPS can process a variety of data formats on
the print server. It converts the print-job data
into the final language/format of the printer via a
series of filters.
•The filtering process works by taking input data
pre-formatted with six arguments i.e. the job ID
of the print job, the user-name, the job-name,
the number of copies to print, any print options
& the filename.
52. BACKEND:
•The backends are the ways in which CUPS
sends data to printers.
•There are several backends available for CUPS
like parallel, serial, and USB ports, cups-pdf[28]
PDF Virtual Printing, as well as network backends
that operate via the IPP.
Alternately,root@techinx# chkconfig telnet onTo start telnet server type command:root@techinx# /etc/init.d/xinetd restart
If none of the commands work, you can try ABORThowever, this command serves only to end Telnet on your end, sometimes leaving it running on the remote host computer, so use ABORT only as your last option.
Characters cannot be directly passed to OS, not designed in that way to receive char from Telnet server, can receive from terminal driver.
The key point is that, in order for any byte to be accepted as a command, it must be preceded by a byte with value 255 - "Interpret as Command" (IAC). Otherwise, the server program assumes that that byte is simply data that will be understood by the application program.
This command proposes negotiation about terminal type.
Option Negotiation
Using internal commands, TELNET in each host is able to negotiate options.
The starting base of negotiation is the NVT capability: each host to be connected must agree to this minimum.
Every option can be negotiated by the use of the four command codes WILL, WON'T, DO, DON'T described above.
In addition, some options have sub-options: if both parties agree to the option, they use the SB and SE commands to manage the sub-negotiation.
Here is a simplified example of how option negotiation works.
Some editing programs, such as vi and Edit, can be run over a Telnet connection; however, these interactive programs are not true GUI programs because cursor movement is controlled by the keyboard, not the mouse.
When you log into a remote host using Telnet, your username and password are sent “in the clear” – meaning, in plain text and not encrypted in any way.
That means your credentials can be (relatively) easily intercepted and used to gain access to that device. For this reason (and many others) Telnet has been largely replaced by the more secure SSH protocol.
NIS is similar to the Internet's domain name system (DNS) but somewhat simpler and designed for a smaller network. It's intended for use on local area networks.