No networking class is complete without dragging out the good old Open Systems Interconnection (OSI) reference model. The OSI model abstracts network communications into seven separate layers. Each layer (in theory) hides their inner workings from the others while performing some critical function. It is important to note that this is a “model” meaning many protocols/real world network implementations do not fit neatly into each layer. If you are interested in some of the history surrounding the OSI model, check out my other post on ARPANET.
The OSI Model
|1||Physical||cables, hubs||Physical layer of most Layer 2 devices|
|2||Data Link||switches||802.3 Ethernet, 802.11 WiFi|
|3||Network||routers, layer 3 switches||IPv4, IPv6, IPsec, ICMP, routing protocols (like BGP)|
|5||Session||NA||Often combined with Application Layer in TCP/IP model. OSI refers to this layer as containing control and/or tunneling protocols (NetBIOS)|
|6||Presentation||NA||Often combined with Application Layer in TCP/IP model. OSI refers to this layer as containing application encryption protocols (SSL/TLS, MIME)|
|7||Application||everything else||DNS, FTP, FTPS, HTTP, HTTPS, IMAP4, POP3, LDAP, RDP, SSH, Telnet, SMTP, SNMP, SFTP, etc.|
Throughout my 10 year career I have worked as a web developer, systems administrator, software engineer, security analyst and now cybersecurity engineer. I currently develop software applications to automate security vulnerability and compliance scanning and reporting for a multinational financial institution.