Considerations for the LAN
Cisco’s AVVID solutions all impact the data network because heavier data flow is
now possible when all of the AVVID functions are used.To avoid congestion and
assure proper voice quality, Cisco created what is known as Voice VLAN ID
(VVID) that segregates traditional data from voice data. In voice-capable devices,
the VVID is used to provide that segregation of data flows to assure the Quality
of Service (QoS) and Class of Service (CoS) needed. Both the Ethernet switches
and gateway must support these services, which means that the enterprise version
of these devices will be used. Consider the traditional data network, which is
shown in Figure 10.1.
This is a very simplified view of a common network, which contains users,
servers, a network-attached server, and a connection to the public Internet. More
advanced networks simply contain more of each of these components, and are
attached together in various configurations. For this discussion, we’ll evolve
Figure 10.1 into a more complex network that is typical of small sites that may
decide to use VoIP solutions. Next, let’s consider the typical telephone system
found in most small offices.Whether the office has 3 users or 30, the basic format
of the office communications is the same (see Figure 10.2).
These two systems are separate and distinct in every way, and are serviced by
two different service and professional providers. For the most part, the data network
professionals have very little, if any, idea of how the telephone system
works.The reverse is true for the telephone system maintainers.Thus, the business
owner of this small site has two maintainers to work with, to order services from,
and to maintain contracts with for these services.