Computer Network Protocols

Network protocols can be classified by the OSI layer where they operate.

Computer Network Protocols by OSI Layer

This section informs lists computer network protocols by their OSI layer.

OSI layer are, in incremental order:

  1. Physical
  2. Data link
  3. Network
  4. Transport
  5. Session
  6. Presentation
  7. Application

Data Link OSI Layer Protocols

Data link OSI layer protocols featured on this post:

  • Ethernet
  • SLIP
  • PPP
    • PPPoE

PPP, PPPoE and Ethernet are part of the network layer of the TCP/IP framework.

EAP over LAN (EAPOL) is the name that receives the EAP authentication protocol when is is used in OSI layer 2. Unlike the other protocols in this list, this is an authorization protocol rather than a communication protocol. To read more about EAP, you can read this post.


Ethernet is a data link protocol.

It uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD) technology.



Serial Line Internet Protocol (SLIP) had no authentication.

It was superseded by PPP.


Point-to-Point Protocol (PPP) is a network encapsulation protocol.

It is no longer the default data link protocol, but it was the foundation for many other protocols that appeared later.

It is an internet standard documented in RFC 1661, and replaced Serial Line Internet Protocol (SLIP).

The original authentication options for PPP were PAP, CHAP and EAP. You can read more about these authentication protocols on this post.


Point-to-Point over Ethernet (PPPoE) is a network protocol.

It encapsulates PPP in ethernet.

Network OSI Layer Protocols

The maximum transmission unit (MTU) is the size of the largest protocol data unit (PDU) that can be communicated in a single network layer transaction

An access control list (ACL) permits or denies packets according to rules

Network Routing Protocols

You can read more about network routing protocols on this post.


Internet Protocol (IP) is probably the most extended network protocol.

You can find more information about IPv4 on this post.

You can find more information about IPv6 on this post.

Dual-Stack Lite (DS-Lite) is a transition mechanism that allows IPv4 and IPv6 to coexist.


Internet Control Message Protocol (ICMP) is a supporting protocol. It is used behind the ping command.

ping can be used to make a rough topology, based on these hints:

  • The time to live (TTL) can provide info about at how many hops the device is.
  • Some firewalls responds differently to pings than endpoints.

You can read more about hping3 command on this post.

You can read more about Windows ping command on this post.

Smurf attack is based on ping command. You can read more about it on this post.

Spanning Tree Protocol (STP)

Spanning Tree Protocol (STP) is a network protocol that builds a loop-free logical topology for Ethernet networks. The basic function of STP is to prevent bridge loops and the broadcast radiation that results from them.

Transport OSI Layer Protocols

Transport layer protocols are mainly:

  • TCP
  • UDP

You can find read more about Transport OSI layer protocol on this post.

Network+Transport Protocol

There are some protocols that do not fit into either network or transport layers, and belong to both of them:

  • VPN protocols

VPN Protocols

Virtual Private Networks (VPN) do not fit well within the OSI model.

You read more about VPN and their protocols on this post.

Presentation OSI Layer Protocols

JPEG, MIDI, etc.


Transport Layer Security (TLS) substitutes the now deprecated protocol SSL.

In the TLS handshake, and asymmetric encryption protocol is used to exchange a session-specific shared key with which further communication is encrypted using symmetric encryption.

Application OSI Layer Protocols

Application layer protocols:

  • E-mail
  • SSH
  • DNS
  • SNMP
  • WebSocket


You can find a list of e-mail protocols on this post.


Secure connection protocol (SSH).


Domain Name System (DNS).

You can read more about it on this post.


Simple Network Management Protocol (SNMP).

You can read more about it on this post.


WebSocket is a protocol that provides simultaneous two-way communication channels over a single Transmission Control Protocol (TCP) connection.

You can read more about WebSockets on this post.

Multilayer Protocols

Multilayer protocols bring these issues:

  • They can conceal covert channels (and thus covert channels are allowed)
  • Filters can be bypassed by traffic concealed in layered protocols
  • The logical boundaries put in place by network segments can be bypassed under some circumstances.

Multilayered protocols featured on this post:

  • Converged protocols
    • SAN
    • FCoE
    • MPLS
    • iSCSi
  • VoIP
  • DNP3

Converged Protocols

Converged protocols are the merging of specialty or proprietary protocols with standard protocols, such as those from the TCP/IP suite.

  • Storage Area Network (SAN)
  • Fibre Channel over Ethernet (FCoE)
  • Multiprotocol Label Switch (MPLS)
  • Internet Small Computer System Interface (iSCSI)
Fiber Channel over Ethernet (FCoE)

It is a networking protocol that supports Fibre Channel natively over Ethernet


Multiprotocol Label Switch (MPLS). You can read more about it on this post.

Internet Small Computer System Interface

iSCI allows location-independent file services over traditional network technologies. It is used to link storage facilities, and it costs less than traditional Fibre Channel.


You can read more about VoIP on this post.


Distributed Network Protocol 3 (DNP3). You can read more about DNP3 on this post.

Computer Network Security Protocols

Computer network security protocols are aimed on ensuring the CIA (confidentiality, integrity and availability) triad.

Network Confidentiality Protocols

You can read find a list of network access protocols that ensure confidentiality on this post about identify and access management.

Network Availability Protocols

Quality of Service (QoS) is a control to ensure the availability of the network.

There is IP QoS in OS layer 3 and TPC/UDP QoS in OSI layer 4.

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