Studying for GAIC and just seeing if I can write these from memory.
We use the OSI model to talk about network layers and the TCP/IP model to implement.
OSI Model
(P)lease (D)o (N)ot (T)hrow (S)ausage (P)izza (A)way
Physical layer (layer 1) - transmission of raw binary data (0's and 1's). Typically via electrical (Ethernet), Radio Frequency (Wireless) or photo optics (Fiber).
Data Link Layer (layer 2) - Switches typically operate at this layer. This is the logical layer - where the data has meaning as opposed to raw binary data.
Network Layer (layer 3) - routing layer - where most routers operate and determine the path the data will take through the network. Some switches, referred to routing switches, operate at this layer.
Transport Layer (Layer 4) - packages and orders data as it flows through the network.
Session Layer (Layer 5) - virtual connection between two points for transmission of data.
Presentation Layer (Layer 6) - transforms the data into machine independent data that can be read by any computer, whether big endian (left to right) or little endian (right to left).
Application Layer (Layer 7) - the layer that handles providing particular needed network services to the application (HTTP, FTP, etc.)
The TCP/IP Model
The TCP/IP Model has four layers but some layers are just a combination of the above layers. There are still 7 layers we just group them together in the TCP/IP model as follows:
Network - Layers 1 and 2
Internet - Layer 3
Transport - Layer 4
Application - Layer 5, 6, 7
Devices & Tools
NICs operate in Layer 1 and Layer 2, handling transmission of binary data via ethernet, token ring, wireless.
Sniffers operate at layer 2.
Switches natively operate at layer 2 though some have layer 3 routing capabilities and blade systems may allow for firewall.
Routers operate at layer 3. They use the IP to determine which network to go next but use ARP, routing tables and MAC addresses to get the packet from one hop to the next.
Firewalls operate at layer 3 or layer 4.
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Not too shabby. Didn't have to look anything up :)
On to header analysis and protocols.
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