2.1: TCP and UDP

TCP and UDP

Used to move data across IP networks; operates at OSI Layer 4 and supports multiplexing to allow many applications to communicate at once.

TCP (Transmission Control Protocol)

A connection-oriented protocol that ensures reliable delivery, error recovery, message ordering, and flow control.

UDP (User Datagram Protocol)

A connectionless protocol that offers unreliable delivery, no error recovery, and no flow control.

UDP

Protocol best suited for real-time communication like DHCP or TFTP, where speed is more important than reliability.

TCP

Connection-oriented protocols like HTTPS and SSH that provide delivery confirmation and manage frame order.

Non-Ephemeral Ports

Ports that are well-known and registered. Used by server applications to listen for incoming connections. Manually assigned. Ports 0-1023 (Well-known), 1024-49151 (registered)

Ephemeral Ports

Ports automatically and temporarily assigned by OS when a client makes a request. Ports 49152-65535

FTP (File Transfer Protocol)

Transfers files between computers

FTP Port(s)

TCP 20 (data) and TCP 21 (control)

SSH

Secure, encrypted remote command-line access to another computer over an unsecured network

SSH Port(s)

TCP 22

Telnet

Unencrypted remote command-line access; insecure as it sends data in plain text

Telnet Port(s)

TCP 23

SMTP (Simple Mail Transfer Protocol)

A protocol used for SENDING emails across networks (Gmail, Outlook, etc.) Sends emails from your device or mail client to an email server

SMTP Port(s)

TCP 25

DNS (Domain Name System)

A hierarchical system that translates domain names into IP addresses, allowing users to access websites using human-readable addresses.

DNS Port(s)

UDP 53 and TCP 53

DHCP (Dynamic Host Configuration Protocol)

A network management protocol used to automatically assign IP addresses and other network configuration settings to devices on a network.

DHCP Port(s)

UDP 67 and UDP 68

HTTP (Hyper-Text Transfer Protocol)

A protocol used for transmitting hypertext via the internet, allowing web browsers and servers to communicate.

HTTP Port(s)

UDP 80

HTTPS (Hyper-Text Transfer Protocol Secure)

A secure version of HTTP that uses encryption to protect the communication between web browsers and servers.

HTTPS Port(s)

TCP 443

POP3 (Post Office Protocol version 3)

A protocol used by email clients to RETRIEVE emails from a mail server. It allows users to DOWNLOAD messages to their local devices while keeping the emails stored on the server.

POP3 Port(s)

TCP 110

IMAP (Internet Message Access Protocol version 4)

ACCESSES and SYNCHRONIZES emails on the server from multiple devices

IMAP Port(s)

TCP 143

SMB (Server Message Block)

Windows network file sharing protocol. Applications and users can read, write, and manage files/printers on a remote server

SMB Port(s)

TCP 445 (direct transport, modern standard), UDP 137/TCP 139 (NetBIOS, rarely used)

SNMP (Simple Network Management Protocol)

Protocol to monitor, manage, and configure devices remotely

SNMP Port(s)

UDP 161 (queries) and UDP 162 (alerts)

LDAP (Lightweight Directory Access Protocol)

Access and manage directory services (centralized databases with info about users, groups, devices and more).

Used to authenticate users, authorize access to network resources, query directory data (find a user, device, or group), and manage organizational info

LDAP Port(s)

TCP 389

RDP (Remote Desktop Protocol)

Remotely access desktops and applications

RDP Port(s)

TCP 3389