Introduction to IP




TCP and UDP
  • Transported inside IP
  • Two ways to move data from place to place (TCP and UDP)
  • OSI Layer 4 (The transport layer)
  • Multiplexing (meaning - incorporate into a multiplex signal or system.)
    • Use many different applications at the same time
TCP (Transmission Control Protocol)
  • TCP is connection-oriented. It establishes a logical end-to-end connection between the two communication hosts. Control information, called a handshake, is exchanged between the two endpoints to establish a dialogue before data is transmitted. (source - oreilly) A formal connection setup and close.
    • "Reliable" deliver
      • Recovery from errors
      • Can manage out-of-order messages or retransmissions
    • Flow control
      • The receiver can manage how much data is sent
UDP - User Datagram Protocol
  • Connectionless. Refers to network protocols in which a host can send a message without establishing a connection with the recipient. That is, the host simply puts the message onto the network with the destination address and hopes that it arrives. (source - webopedia) No formal open or close to the connection.
  • "Unreliable" delivery - No error recovery
    •  No reordering of data or retransmissions
  • No flow control
    • Sender determines the amount of data transmitted.

Ports - meaning - (n) a town or city with a harbor where ships load or unload, especially one where customs officers are stationed.
              computing - (v, n) transfer (software) from one system or machine to another.
  • IPv4 sockets
    • Server IP address, protocol, server application port number
    • Client IP address, protocol, client port numbers
  • Non-ephemeral ports and Ephemeral ports
    • Ephemeral - meaning (adj) - lasting for a very short time. (n) an ephemeral plant.
    • Non-ephemeral ports - permanent port numbers
      • ports 0 through 1,023
      • Usually on a server or service
    • Ephemeral ports - temporary port numbers
      • Ports 1,024 through 65,536
      • Determined in real-time by the clients
  • Port Numbers
    • TCP and UDP ports can be any number between 0 and 65,536
    • Most servers (services) use non-ephemeral (not-temporary) port numbers
      • This is not always the case - it's just a number.
    • Port numbers are for communication, not security
    • service port numbers need to be "well known"
    • TCP port numbers aren't the same as UDP port numbers
  • ICMP - Internet Control Message Protocol
    • "Text messaging" for our network devices
    • Another protocol carried by IP - Not used for data transfer
    • Devices can request and reply to administrative request
    • Devices can send messages when things don't go well
  • FTP - File Transfer Protocols
    • tcp/20 (active mode data), tcp/21 (control)
    • Transfers files between systems
    • Authenticates with a username and password
    • full-featured functionality (list, add, delete, etx.)
  • SSH - Secure Shell
    • Encrypted communication link - tcp/22
    • Looks and acts the same as Telnet
  • SFTP - Secure FTP
    • Uses the SSH File Transfer Protocol - tcp/22
    • Provides file system functionality
      • Resuming interrupted transfers, directory Listings, remote file removal
  • Telnet - Telecommunication Network
    • tcp/23
    • login to devices remotely
    • Console access
    • In-the-clear communication
    • Not the best choice for production systems
  • POP/IMAP
    • Receive emails from an email server
      • Authenticate and transfer
    • POP3 - Post office protocol version 3 - tcp/110
      • Basic mail transfer functionality
    • IMAP4 - Internet Message Access Protocol v4 - tcp/143
      • Manage email inbox from multiple clients
  • LDAP/LDAPS
    • LDAP (Lightweight Directory Access Protocol) - tcp/389
      • Store and retrieve information in a network directory
    • LDAPS (LDAP Secure) - tcp/636
      • A non-standard implementation of LDAP over SSL
  • SMB - Server Message Block
    • Protocol used by Microsoft Windows
      • File sharing, printer sharing
      • Also called CIFS (Common Internet File System)
    • Direct over tcp/445 (NetBIOS-less)
      • Direct SMB communication over TCP without the NetBIOS transport
  • H.323
    • Voice over IP(VoIP) signaling - tcp/1720
      • ITU Telecommunication H.32x protocol series
    • Setup and manage VoIP sessions
      • Call, ring, hang up
    • One of the earliest VoIP standards
      • Still in use today
  • RDP - Remote Desktop Protocol
    • Share a desktop from a remote location over tcp/3389
    • Remote Desktop Services on many Windows versions
    • Can connect to an entire desktop or just an application
    • Clients for Windows, MacOS, Linux, iPhone, and others
  • SIP - Session Initiation Protocol
    • Voice over IP (VoIP)signaling
      • tcp/5060 and tcp/5061
    • Setup and manage VoIP sessions
      • Call, ring, hang up
    • Extend voice communication
      • Voice conferencing, instant messaging, file transfer, etx.
  • DNS - Domain Name System
    • Converts name to IP addresses - udp/53
      • www.mmpnw.com = 172.217.20.115
    • These are very critical resources
      • Usually multiple DNS servers are in production
  • DHCP - Dynamic Host Configuration Protocol
    • Automated configuration of IP address, subnet mask and other options
      • udp/67, udp/68 - Requires a DHCP server
    • Dynamic / pooled
      • IP addresses are assigned in real-time from a pool
      • Each system is given a lease
      • Must renew at set intervals
    • Reserved
      • Addresses are assigned by MAC address
      • Quickly manage addresses from one location
  • NTP - Network Time Protocol
    • Switches, routers, firewalls, servers, workstations
      • Every device has its own clock - udp/123
    • Synchronizing the clocks becomes critical
      • log files, authentication information, outage details
    • Automatic updates
      • No flashing 12:00 lights
    • Flexible - You control how clocks are updated
    • Very accurate
      • Accuracy is better than 1 millisecond
  • SNMP - Simple Network Management Protocol
    • Gather statistics from network devices
      • upd/161
    • v1 - The original
      • Structured tables, in-the-clear
    • v2 - A good step ahead
      • Data type enhancements, bulk transfers
      • Still in-the-clear
    • v3 - The new standard
      • Message integrity, authentication, encryption
  • HTTP and HTTPS
    • Hypertext Transfer Protocol
      • Communication in the browser
      • And by other applications
    • In the clear or encrypted
      • supported by nearly all web servers and clients


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