Essential Network Protocols: Layers, Addressing, and Communication

Understanding Core Network Protocols and Services

Introduction to Network Fundamentals

• The Internet Control Message Protocol (ICMP) is an IP protocol used for sending control, reporting, and discovery messages.
• Network architectures are built upon dependent levels or layers.
• The complexity of a network directly impacts its reliability.
• Virtual communication is a fundamental aspect of modern media.
• End-to-end flow control is a critical network function.

Transport Layer Protocols: TCP and UDP

• An advantage of including the transport level is that protocols can be designed to conceal underlying network complexities from applications.
• The primary data unit at the transport layer is the Transport Protocol Data Unit (TPDU).
• Transport level protocols include TCP and UDP.

TCP: Reliable, Connection-Oriented Communication

• TCP (Transmission Control Protocol) is a reliable, streaming protocol that strives for ordered and error-free delivery.
• TCP's design leverages IP (Internet Protocol), which is a network layer protocol.
• TCP uses IP addresses for host identification.
• The ACK control bit signifies the acknowledgment field number, confirming receipt of data.
• The SYN control bit is used to request a segment and initiate a connection.
• The interface between TCP and applications is a port.
• Commonly recognized ports are in the range [1-255].
• A socket is defined as a pair consisting of an IP address and a port number.
• At each connection, a pair of sockets is used to uniquely identify the communication endpoints.
• TCP data blocks are referred to as segments.
• TCP controls flow based on acknowledgments (ACKs) received from windows, managing data transmission rates.
• The Maximum Segment Size (MSS) significantly impacts the effectiveness of TCP communication.
• Source ports are typically identified by the first bytes in a segment header.
• Reliability is one of the key situations TCP is designed to address.
• The RECEIVE function is an integral part of the TCP protocol for data reception.
• The CLOSE function indicates that the client wishes to terminate the connection.

UDP: Connectionless Datagram Service

• UDP (User Datagram Protocol) is a connectionless-oriented protocol, offering a simpler, faster, but less reliable service.

Network Naming and Addressing: DNS and NetBIOS

• Process addressing involves the implementation of specific processes for communication.
• Network media often relies on resident protocols for operation.
• The Novell protocol SPX (Sequenced Packet Exchange) is a legacy network protocol.
• NetBIOS (Network Basic Input/Output System) has a flat naming structure.
• WINS servers (Windows Internet Name Service) convert NetBIOS names to IP addresses.
• Communication primarily occurs at application levels.
• Protocols operating at higher levels are often referred to as high-level protocols.
• A domain is defined as a group of associated computers or network resources.
• A domain name is a series of characters used to identify a domain.
• Generic top-level domains (gTLDs) are found at the first level of the DNS hierarchy.
• Domain names provide complete addresses for network resources.
• A zone in DNS is a distributed database containing resource records.
• The fundamental elements within a DNS zone are Resource Records (RRs).
• Common RRs include A (for IPv4 addresses) or AAAA (for IPv6 addresses).
• DNS servers maintain up-to-date copies of zone information.
• A query is the operation of requesting a name resolution from a DNS server.
• DNS resolution often involves prioritizing certain records or responses.

Application Layer Protocols and Services

• Programs that send commands to remote systems are typically terminal emulators.
• The Telnet protocol establishes a TCP connection for remote terminal access.
• Linux systems commonly use the SSH protocol (Secure Shell) for secure remote access.
• A key function of the application level is the maintenance of information and data integrity.
• A file system is the system that runs on the computer to manage files.
• A directory service provides organized access to network resources and information.
• Protocols can enable virtual communication and resource access.
• The FTP protocol (File Transfer Protocol) allows for file handling and transfer.
• The HTTP protocol (Hypertext Transfer Protocol) is the protocol that generates and serves web content.
• HTML (Hypertext Markup Language) is the hypertext language used for creating web pages.
• The SMTP protocol (Simple Mail Transfer Protocol) addresses user email needs for sending messages.
• When SMTP is used for mail routing, it relies on MX (Mail Exchanger) records.
• Every email account typically uses a POP3 server (Post Office Protocol version 3) for receiving mail.
• Telnet protocols rely on TCP for reliable data transmission.
• NCPs (NetWare Core Protocols) manage file and print services from a central location.

Network Infrastructure and Routing

• Gateways are essential for routing of information between different networks.
• A routing table or path is used to establish routes for data packets.