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Protocols
A protocol is a set of rules and guidelines for communicating data. Rules are defined for each step and process during communication between two or more computers. Networks have to follow these rules to successfully transmit data.



IEEE 802.11

  • IEEE 802.11 is part of the IEEE 802 set of LAN protocols, and specifies the set of media access control (MAC) and physical layer (PHY) protocols for implementing wireless local area network (WLAN) Wi-Fi computer communication in various frequencies, including but not limited to 2.4, 5, and 60 GHz frequency bands.
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  • Applications and Tools
  • References
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  • IEEE 802.11 Wi-Fi protocol summary

    Protocol Frequency Channel Width MIMO Maximum data rate (theoretical)
    802.11ax 2.4 or 5GHz 20, 40, 80, 160MHz Multi User (MU-MIMO) 2.4 Gbps 1
    802.11ac wave2 5 GHz 20, 40, 80, 16MHz Multi User (MU-MIMO) 1.73 Gbps 2
    802.11ac wave1 5 GHz 20, 40, 80MHz Single User (SU-MIMO) 866.7 Mbps 2
    802.11n 2.4 or 5 GHz 20, 40MHz Single User (SU-MIMO) 450 Mbps 3
    802.11g 2.4 GHz 20 MHz N/A 54 Mbps
    802.11a 5 GHz 20 MHz N/A 54 Mbps
    802.11b 2.4 GHz 20 MHz N/A 11 Mbps
    Legacy 802.11 2.4 GHz 20 MHz N/A 2 Mbps
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  •      1 2 Spatial streams with 1024-QAM modulation.
         2 2 Spatial streams with 256-QAM modulation.
         3 3 Spatial streams with 64-QAM modulation.
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  • 802.11ax (Wi-Fi 6)
    • Ratification expected in Q4 2019.
    • Supports both 2.4 & 5 GHz
    Mode Maximum rate Antenna transmit /
    Receive arrangements
    1x1 20 MHz 143 Mbps 1 TX (Transmit, Upload)
    1 RX (Receive, Download)
    2x2 20 MHz 287 Mbps 2 TX
    2 RX
    1x1 40 MHz 287 Mbps 1 TX
    1 RX
    2x2 40 MHz 574 Mbps 2 TX
    2 RX
    1x1 80 MHz 601 Mbps 1 TX
    1 RX
    2x2 80 MHz 1.2 Gbps 2 TX
    2 RX
    1x1 160 MHz 1.2 Gbps 1 TX
    1 RX
    2x2 160 MHz 2.4 Gbps 2 TX
    2 RX
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  • 802.11ac wave2
    • Released in June 2016.
    • Key New Features for Wi-Fi clients:
      • Multi-User MIMO
      • 160 MHz channels
    Mode Maximum rate Antenna transmit /
    Receive arrangements
    1x1 40 MHz 200 Mbps 1 TX (Transmit, Upload)
    1 RX (Receive, Download)
    2x2 40 MHz 400 Mbps 2 TX
    2 RX
    1x1 80 MHz 433 Mbps 1 TX
    1 RX
    2x2 80 MHz 866 Mbps 2 TX
    2 RX
    1x1 160 MHz 866 Mbps 1 TX
    1 RX
    2x2 160 MHz 1.73 Gbps 2 TX
    2 RX
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  • 802.11ac wave1
    • Released in January 2014.
    • Data rates varying modulation types and number of spatial streams; 200 Mbps, 400 Mbps, 433 Mbps, 600 Mbps, 867 Mbps. See table below.
    • 24 non-overlapping unlicensed national information infrastructure (UNII) channels in 5 GHz frequency band.
    Mode Maximum rate Antenna transmit /
    Receive arrangements
    1x1 40 MHz 200 Mbps 1 TX
    1 RX
    2x2 40 MHz 400 Mbps 2 TX
    2 RX
    1x1 80 MHz 433 Mbps 1 TX
    1 RX
    2x2 80 MHz 866 Mbps 2 TX
    2 RX
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  • 802.11n
    • Data rates with varying modulation types: 1, 2, 5.5, 6, 9, 11, 12, 18, 24, 36, 48, 54 Mbps (see table below)
    • Orthogonal frequency-division multiplexing (OFDM) using multiple-input/multiple-output (MIMO) and channel bonding (CB)
    • Three non-overlapping channels in industrial, scientific, medical (ISM) frequency band at 2.4 GHz
    • 12 non-overlapping unlicensed national information infrastructure (UNII) channels in 5 GHz frequency band with and without CB
    Note We recommend channel bonding for the 5 GHz because there are a limited number of non-overlapping channels available in the 2.4 GHz band.
    Mode Maximum rate Antenna transmit /
    Receive arrangements
    1x1 20 MHz 72.2 Mbps 1 TX
    1 RX
    1x1 40 Mhz 150 Mbps 1 TX
    1 RX
    2x2 20 MHz 144.4 Mbps 2 TX
    2 RX
    2x2 40 MHz 300 Mbps 2 TX
    2 RX
    3x3 20 MHz 216.7 Mbps 3 TX
    3 RX
    3x3 40 MHz 450 Mbps 3 TX
    3 RX
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  • 802.11g
    • Released in 2003.
    • Data rates with varying modulation types: 6, 9, 12, 18, 24, 36, 48 and 54 Mbps; can revert to 1, 2, 5.5, and 11 Mbps using DSSS and CCK.
    • Orthogonal frequency-division multiplexing (OFDM) with 52 subcarrier channels; backwards compatible with 802.11b using DSSS and CCK.
    • Three non-overlapping channels in industrial, scientific, medical (ISM) frequency band at 2.4 GHz.
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  • 802.11a
    • Released in 1999.
    • Data rates with varying modulation types: 6, 9, 12, 18, 24, 36, 48 and 54 Mbps.
    • Orthogonal frequency-division multiplexing (OFDM) with 52 subcarrier channels.
    • 12 non-overlapping unlicensed national information infrastructure (UNII) channels in 5 GHz frequency band.
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  • 802.11b
    • Released in 1999.
    • Data rates with varying modulation types: 1, 2, 5.5 and 11 Mbps.
    • High-rate direct-sequence spread spectrum (HR-DSSS).
    • Three non-overlapping channels in industrial, scientific, medical (ISM) frequency band at 2.4 GHz.
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  • Legacy 802.11
    • Released in 1997.
    • Two raw data rates of 1 and 2 Mbps.
    • Frequency hopping spread spectrum (FHSS) or direct-sequence spread spectrum (DSSS).
    • Three non-overlapping channels in industrial, scientific, medical (ISM) frequency band at 2.4 GHz.
    • Originally defined carrier sense multiple access with collision avoidance (CSMA-CA).


Address Resolution Protocol (ARP)


Domain Name System (DNS)

  • DNS is a hierarchical decentralized naming system for computers, services, or other resources connected to the Internet or a private network. UDP port 53, by default. If the data portion of the UDP packet exceeds the maximum size, then TCP port 53 is used.
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  • Applications and Tools
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  • References
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  • DDNS
  • DDNS
    • ChangeiP Free Dynamic DNS delivers the essentials DNS features including a free to use subdomain, unlimited URL redirections, and complete port redirection capabilities.
    • D-Link - dynamic DNS host name for your D-Link router
    • DNSdynamic is free, secure, unlimited dynamic DNS (DDNS), and free VPN to our users.
    • My DDNS is a free solution I developed.
    • no-ip allows remote access your computer, DVR, webcam, security camera or any internet connected device easily. Dynamic DNS points an easy to remember hostname to your dynamic IP address.
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  • DNS over HTTPS (DoH)


Dynamic Host Configuration Protocol (DHCP)


File Transfer Protocol (FTP)

  • FTP is a standard network protocol used for the transfer of computer files between a client and server on a computer network.
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  • Commands
    binarySets the file transfer type to binary. Critical to the successful transfer of files such as Word documents, graphics, or software packages; also works fine with text files (files that contain only ascii text and no formatting).
    get $filenameTransfers a file from a remote computer to the computer you are typing on.
    mget $file1 $file2Transfers multiple files from a remote computer to the computer you are typing on.
    lsLists all the files in your current sub-directory.
    cdChanges the directory. To move back up to a previous level, use \"cd ..\" (note the space).
    put $filenameTransfers a file from the computer you are typing on to the remote computer.
    mput $file1 $file2Transfers multiple files from the computer you are typing on to the remote computer.
    pwdTells you the present working directory.
    <Ctrl>+hDeletes a character to the left of the cursor (acts as a backspace). Note: Use the Ctrl key; don't type the word "Ctrl".
    help $commandDisplays the definition of a command. Type \"help\" to see a full list of valid commands.
    byeEnds the FTP session.
  • References


Hypertext Transfer Protocol (HTTP) / Hypertext Transfer Protocol Secure (HTTPS)


Internet Message Access Protocol (IMAP)

  • IMAP is an Internet standard protocol used by e-mail clients to retrieve e-mail messages from a mail server over a TCP/IP connection.
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  • References


Internet Protocol version 4 (IP) / Internet Protocol version 6 (IPv6)

  • IP is the principal communications protocol in the Internet protocol suite for relaying packets across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet.
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  • Applications and Tools
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  • Special Use Subnets
    0.0.0.0/8self-identification
    10.0.0.0/8Private
    127.0.0.0/32Loopback
    169.254/16DHCP link local address
    172.16.0.0/12Private
    192.0.0.0/24Special Purpose
    192.0.2.0/24TEST-NET-1
    192.88.99.0/246to4 relay anycast
    192.88.99.2/326to4 relay anycast
    192.88.99.2/326to4 relay anycast
    192.168.0.0/16Private
    198.18.0.0/15Interconnect Device
    198.51.100.0/24TEST-NET-2
    203.0.113.0/24TEST-NET-3
    224.0.0.0/4Multicast
    240.0.0.0/4Reserved
    255.255.255.255/32Limited broadcast
    fc00::/7Unique Local Unicast
    fe80::/10Link Local Unicast
    ff00::/8Multicast
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  • IP Assignment
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  • References


Lightweight Directory Access Protocol (LDAP)

  • LDAP is an open, vendor-neutral, industry standard application protocol for accessing and maintaining distributed directory information services over an Internet Protocol (IP) network.
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  • Commands
    ldapbindUse ldapbind to authenticate to a directory server or find out if the server is running.
    ldapsearchUse ldapsearch to search for specific entries in a directory. ldapsearch opens a connection to a directory, authenticates the user performing the operation, searches for the specified entry, and prints the result in a format that the user specifies.
    ldapaddUse ldapadd to add entries to the directory. ldapadd opens a connection to the directory and authenticates the user. Then it opens the LDIF file supplied as an argument and adds, in succession, each entry in the file.
    ldapdeleteUse ldapdelete to remove leaf entries from a directory. ldapdelete opens a connection to a directory server and authenticates the user. Then it deletes specified entries.
    ldapmodifyUse ldapmodify to modify existing entries. ldapmodify opens a connection to the directory and authenticates the user. Then it opens the LDIF file supplied as an argument and modifies the LDAP entries specified by the file.
    ldapmoddnUse ldapmoddn to change the RDN of an entry or move an entry or subtree to another location in the directory
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  • References


Network File System (NFS)

  • NFS is a distributed file system protocol allows a user on a client computer to access files over a computer network much like local storage is accessed.
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  • References


Network Time Protocol (NTP)


Post Office Protocol version 3 (POP3)

  • POP is an application-layer Internet standard protocol used by e-mail clients to retrieve e-mail from a server in an Internet Protocol (IP) network.
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  • Commands
    USER Your user name for this mail server
    PASS Your password.
    QUITEnd your session.
    STATNumber and total size of all messages
    LIST Message# and size of message
    RETR $messageRetrieve selected message
    DELE $messageDelete selected message
    NOOPNo-op. Keeps you connection open.
    RSETReset the mailbox. Undelete deleted messages.
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  • Applications and Tools
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  • References


Real-time Transport Protocol (RTP)


Secure Shell (SSH)

  • SSH is a cryptographic network protocol for operating network services securely over an unsecured network.
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  • References


Simple Mail Transfer Protocol (SMTP)

  • SMTP is an Internet standard for electronic mail (email) transmission. Some ways to deal with Spam.
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  • Commands
    ATRNAuthenticated TURN
    AUTHAuthentication
    BDATBinary data
    BURLRemote content
    DATAThe actual email message to be sent
    This command is terminated with a line that contains only a
    EHLOExtended HELO
    ETRNExtended turn
    EXPNExpand
    HELOIdentify yourself to the SMTP server.
    HELPShow available commands
    MAILSend mail from email account
    MAIL FROM: me@mydomain.com
    NOOPNo-op. Keeps you connection open.
    ONEXOne message transaction only
    QUITEnd session
    RCPTSend email to recipient
    RCPT TO: you@yourdomain.com
    RSETReset
    SAMLSend and mail
    SENDSend
    SOMLSend or mail
    STARTTLS
    SUBMITTERSMTP responsible submitter
    TURNTurn
    VERBVerbose
    VRFYVerify
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  • Applications and Tools
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  • References


Simple Network Management Protocol (SNMP)

  • SNMP is used to communicate management information between the network management stations and the agents in the network elements.
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  • SNMP Security Levels
    Version Level Authentication Encryption What Happens
    v1 noAuthNoPriv Community String No Uses a community string match for authentication.
    v2c noAuthNoPriv Community String No Uses a community string match for authentication.
    v3 noAuthNoPriv Username No Uses a username match for authentication.
    v3 authNoPriv Message Digest Algorithm 5 (MD5) or Secure Hash Algorithm (SHA) No Provides authentication based on the Hashed Message Authentication Code (HMAC)-MD5 or HMAC-SHA algorithms.
    v3 authPriv Message Digest Algorithm 5 (MD5) or Secure Hash Algorithm (SHA) Data Encryption Standard (DES) Provides authentication based on the HMAC-MD5 or HMAC-SHA algorithms. In addition to authentication, provides DES 56-bit encryption based on the Cipher Block Chaining (CBC)-DES (DES-56) standard.
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  • Applications and Tools
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  • References


Spanning Tree Protocol (STP) / Rapid Spanning Tree Protocol (RSTP)

  • STP is a network protocol that builds a logical loop-free topology for Ethernet networks.
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  • References
    • IEEE 802.1D IEEE standard for local and metropolitan area networks--Media access control (MAC) Bridges (for STP and RSTP).
    • IEEE 802.1Q IEEE Standards for local and metropolitan area networks-—Virtual Bridged Local Area Networks (for MSTP).
    • Wireshark
    • wikipedia


Syslog Protocol


Transmission Control Protocol (TCP)


User Datagram Protocol (UDP)

  • UDP allows computer applications to send messages to other hosts on an Internet Protocol (IP) network. UDP has no handshaking. UDP packets are dropped on congested networks. Therefore, it is unclear if the message is delivered.
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  • References