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Computers on a network communicate in agreed ways called protocols. Protocols dictate which signals computers use across cables, how they tell one another that they have received information, and how they exchange information.
Protocols are more accurately termed protocol ``stacks'' or protocol ``suites'' because the communications functions are complex and are usually divided into independent layers or levels. A stack is a collection of protocol layers that implement network communication. The protocol associated with each layer communicates only with the layers immediately above and below it, and assumes the support of underlying layers. Lower layers are closer to the hardware and higher layers are closer to the user. The number of layers and tasks that each layer performs depends on which stack you are using.
Supported protocol stacks
| Protocol stack | Provided by SCO OpenServer System | Provided by other SCO OpenServer products | Supported by SCO OpenServer network drivers |
|---|---|---|---|
| TCP/IP | yes | - | yes |
| NetBEUI | - | yes | yes |
SCO OpenServer also provides two operating system packages that permit UNIX and XENIX® systems to communicate as part of a remote network:
Although these packages are not protocol stacks, they are discussed here because they provide low-cost alternatives to LANs based on specialized hardware and software.
The relative advantages of the SCO OpenServer connectivity packages are: