Understanding Network Protocols: Server, Client, and More
Understanding Network Protocols
Server: A host running a software application that provides information or services to other hosts connected to the network.
Client: The name given to a computer application used to access information stored on a server.
Key Network Protocols
- DNS (Domain Name System): Provides the IP address of a website or the domain name for a host to connect to it.
- Telnet: Allows administrators to log in from a remote host and control the host as if the session has been started locally.
- E-mail: SMTP uses POP3 or IMAP to send emails via the Internet. Recipients are specified in the format
user@xyz. - DHCP (Dynamic Host Configuration Protocol): Assigns an IP address, subnet mask, a default gateway, and other information to clients.
- Web (HTTP): Hypertext Transfer Protocol (HTTP) is used to transfer information between web servers and web clients.
- FTP (File Transfer Protocol): Allows uploading and downloading files between a client and a server.
Application and Transport Protocols
Application Protocol: Governs how a web server and a web client interact, defining the format of requests and responses exchanged. It relies on other protocols to regulate message delivery.
Transport Protocol: The Transmission Control Protocol (TCP) manages individual conversations between web servers and web clients. It formats HTTP messages into segments for transmission, providing flow control and acknowledgment of packets.
Internetwork Protocol: The most common is the Internet Protocol (IP). IP is responsible for formatting TCP segments, assigning logical addresses, and encapsulating them into packets for routing to the destination host.
Protocols for Network Access
Protocols for Network Access: These manage data links by taking IP packets and encapsulating them in the frame format corresponding to the local network. These protocols assign physical addresses to the frames and prepare them for transmission over the network.
Standards and Protocols for Physical Media: These govern how bits are represented in the media, how signals are sent, and how receiving hosts interpret these signals.
TCP and UDP
TCP (Transmission Control Protocol): Splits messages into segments, numbers them sequentially, and passes them to IP for packet creation. TCP tracks sent segments and retransmits if acknowledgments are not received. The receiving host reassembles TCP segments.
UDP (User Datagram Protocol): Does not require acknowledgment.
Ports and Sockets
Port: A numeric identifier for each segment, used to track specific conversations and requested destination services. A service can offer multiple services simultaneously.
Source Port: Randomly generated by the sending device to identify a conversation between two devices.
Socket: A combination of the source IP address and destination port number, used to identify the server and the client requesting the service.
DNS (Domain Name System): Provides a method for hosts to request an IP address from a specific DNS server using a hostname. A DNS server contains a table that associates hostnames with corresponding IP addresses. If an entry is not found, it queries other DNS servers within the domain.