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:

Physical
Data link
Network
Transport
Session
Presentation
Application

Data Link OSI Layer Protocols

Data link OSI layer protocols featured on this post:

Ethernet
SLIP
PPP
- PPPoE
HDLC
LAPB
ATM
LLDP

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

Ethernet is a data link protocol.

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

SLIP

Deprecated

Serial Line Internet Protocol (SLIP) had no authentication.

It was superseded by PPP.

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.

PPPoE

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

It encapsulates PPP in ethernet.

HDLC

High-Level Data Link Control (HDLC).

LAPB

Link Access Procedure, Balanced (LAPB) derives from HDLC.

ATM

Asynchronous Transfer Mode (ATM)

LLDP

Link Layer Discovery Protocol (LLDP) is a link-layer protocol used by network devices for advertising their identity, capabilities, and neighbors on a LAN.

It is covered in the standard IEEE 802.1AB with the name Station and Media Access Control Connectivity Discovery.

It was developed as a vendor neutral protocol to minimize the dominant position of Cisco network cards, that used the proprietary Cisco Delivery Protocol, while being compatible with the card of their competitors (such as Alcatel-Lucent, Aruba or IBM).

Frame Relay

Frame Relay transfer packets.

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.

IP

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.

ICMP

Internet Control Message Protocol (ICMP) is a supporting protocol with the purpose of report about issues on packet delivery. 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.

ICMPv6 uses the field “type” to inform about the type of message. For example, the value 128 means that the value is 128.

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.

IGMP

Internet Group Message Protocol (IGMP) is a communications protocol used by hosts and adjacent routers on IPv4 networks to establish multicast group memberships.

Spanning Tree Protocol (STP)

Spanning Tree Protocol (STP) is a network protocol that establishes logical a ethernet network on native Ethernet networks to maintain the topology among the nodes dynamically. 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:

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.

TLS/SSL

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:

HTTP
E-mail
SSH
DNS
SNMP
WebSocket
SIP

HTTP

You can read a post about HTTP.

E-mail

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

SSH

Secure connection protocol (SSH).

DNS

Domain Name System (DNS).

You can read more about it on this post.

SNMP

Simple Network Management Protocol (SNMP).

You can read more about it on this post.

WebSocket

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.

SIP

Session Initiation Protocol (SIP) is a signaling protocol used for initiating, maintaining, and terminating communication sessions that include voice, video and messaging applications.

You can read more on this post about SIP.

H.323

H.323 is a set of protocols to provide audio-visual communication sessions on any packet network.

You can read a post about H.323.

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

MPLS

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

iSCSI

Internet Small Computer System Interface (iSCSI) allows location-independent file services over traditional network technologies. It is used to link storage facilities, and it costs less than traditional Fibre Channel.

iSCSI enables the SCSI protocol to run over IP networks.

An iSCSI Qualified Name (IQN) uses the following format:

iqn.yyyy-mm.naming-authority:unique-name

iSCSI is defined in the standard RFC3720.

VoIP

You can read more about VoIP on this post.

DNP3

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.