By Keith Ferrell  |  Posted 2003-06-01 Print this article Print

What is Application Switching? A way of handling network traffic by identifying and analyzing packets of information before they reach the server.

: Seven Layers for Seven Functions">

REFERENCE: Seven Layers for Seven Functions

The ISO's Open Systems Interconnection (OSI) model describes how data moves within a network, from actual electrons and radio waves (Layer 1) to information within an application (Layer 7). Each layer is dependent on the ones below it for certain services: Layer 3, for example, already translates network addresses, so Layers 4 through 7 can focus on performing other functions. This chart, created with the help of Arcturus Networks, provides a brief overview of the seven layers.
7. Application Telnet, ping, SSH, FTP, HTTP Accept direct interaction—such as password entry, file requests—from the user.
6. Presentation Character mapping, NFS Ensure data is delivered in a format that the recipient can understand.
5. Session DNS, RPC, SIP, H.323 Set up, manage and tear down virtual "circuits" between two computers on a network.
4. Transport TCP, UDP Move data across a network. Known as the "engine" of the OSI stack.
3. Network IP, ICMP, NAT Understand network addresses and choose a route to get there.
2. Data Links ARP, PPP, LCP Break data streams into packages appropriate for the physical connection; detect errors.
1. Physical Fiber optics, ISDN, radio waves, 802.11 Connect to cables, wires and devices.
Source: Arcturus Networks


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