OSI Layer 6 – Presentation 

The presentation layer is concerned with ensuring that communications between systems are in a common and discernable format.

Technologies and implementations at this layer include:

  • Translation services – includes American Standard Code for Information Interchange (ASCII) or Extended Binary Coded Decimal Interchange Code (EBCDIC).
  • Conversion/compression services – includes MPEG, WAV, and others.
  • Encoding – includes encryption.  TLS/SSL for this exam operate above, within, and below the presentation layer.  Do not confuse encoding with encryption!

OSI Layer 7 – Application

This layer includes applications that run on systems.  

Technologies and implementations at this layer:

Dynamic Host Configuration Protocol (DHCP) – a client/server application that assigns IP addresses from pre-determined addresses on the DHCP server.

  • Client – port 67, sends broadcast with a DHCPDISCOVER packet.
  • Server – port 68, sends DHCPOFFER giving client an address.
  • Client – responds with DHCPREQUEST to use that address.
  • Server – replies with DHCPPACK  which binds the client to the IP address.  

Domain Name System (DNS): servers that resolve fully qualified domain names (FQDN) with IP addresses on port 53.  

The domain hierarchy works in a reverse-like fashion.   For example, “top level” refers to the last part of the web address following the dot, or  “.” for example, “.com” would be the root of Amazon.com; this is called the Root or Top Level Domain.

DNS servers require the following records to be operational:

  • Host, aka: “A” or “AAA”
  • Start of Authority (SOA)
  • Name Server (NS)
  • Pointer (PTR)
  • Mail Exchange, or MX
  • Certificate Authority (CAA)

Simple Network Management Protocol (SNMP) – consists of the following:

  • Designed to help manage the network infrastructure
  • Manager (server)
  • Agent (client)
  • Susceptible to brute force of default passwords also known as community strings
  • Network management system
  • Information base
  • Managed devices
  • Agents

Lightweight Directory Access Protocol (LDAP) has the following common attributes:

  • Distinguished Name (DN)
  • Relative Distinguished Name (RDN)
  • Common Name (CN)
  • Domain Component (DC)
  • Organizational Unit (OU)
  • Version 3 supports TLS

HTTP and HTTPS are protocols, and that the browser is the application.  Temporary file storage is the lucrative target because files are unencrypted.

There’s a brief discussion about whether there should be a layer 8 that includes governance, people, processes, and user facing applications. This doesn’t seem like testable material, but it’s in the CBK so there you have it!