The importance of gateway selection is not to be overlooked, whether your
emphasis is on analog or digital protocols or both. Completely understanding all
the equipment’s features and benefits as well as the protocols should help make
this important decision easier to make.
AVVID voice gateways include standalone, IOS-based, and Catalyst switches.
The gateway protocols supported are H.323, MGCP, and Skinny with SIP
gaining ongoing popularity.The voice gateways range from small analog routers
such as the 1750 to large scalable digital T1/E1 7200 routers and everywhere in
between.The gateways can be more traditional VoIP toll bypass or total integrated
all-in-one solutions like the Catalyst 4224.
For small- to medium-sized organizations, the best solution may be either a
Cisco 2600 router or the Catalyst 4224. Either solution should not only be able
to handle VoIP solutions but other AVVID gateway requirements as well.The
2600 Series also has expansion capabilities to help with organizational growth.
However, if you do not require routing capabilities, you might look to the VG200
to provide similar solutions.When looking at the needs of a medium to large
organization, one would have to look at the 3600 Series router, which provides
the scalability necessary to handle the needs of a large enterprise environment.
The 3660 router has the ability to support up to 12 T1, which would consequently
support 2000+ users in a PSTN gateway scenario.The MC3810 would
provide a one step solution for data, voice and video needs. It provides VoFR,
VoIP but also VoATM. However, the MC3810 does not have the modular flexibility
of the 2600 or 3600 routers. It also does not integrate with CallManager.
When you are looking for switch-based solutions with similar functionality, as
the 2600/3600 Series routers do, the Catalyst 4000 would be a good choice. It
supports the same modules as the 2600/3600 except for the high-density voice
module, NM-HDV-XXX. For large organizations seeking high capacity and performance,
the choice could be the 7200 or 7500 routers with the ability to support
up to 20 T1s or 18 E1s via T1/E1 CAS or PRI signaling. A large-scale
switch-based solution would be the Catalyst 6500 series utilizing the 8-port
T1/E1 voice module. Since the release of the Catalyst 6513, which has 13 slots, it
could theoretically scale up to 96 T1 ports providing 2300+ voice channels. Most
likely the configuration would allocate some of the ports as T1 and others as DSP
resources, which will be discussed in Chapter 6.
The IP/VC 3500 videoconferencing products round out the gateways for
the AVVID architecture.They cover multipoint conference units, gateways, and
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terminal adapters.The IP/VC provides solutions in multipoint conferencing,
H.320 to H.323 translation, and legacy H.320 connectivity, while the MCM
completes the videoconferencing solution by providing the gatekeeper functionality
required for Video over IP.
The IP/VC 3510 MCU is a multiparticipant video and data conferencing
solution, whereas the IP/VC 3520 & 3525 gateways are used as ISDN H.320 to
IP H.323 gateways.The main difference between the latter two models is that the
3520 supports V.35 and ISDN BRI interfaces while ISDN PRI is available on the
3525.The IP/VC 3510 connects ISDN-based H.320 systems like a PictureTel
Venue 2000 to the IP-based H.323 network. Another MCU unit provided by
Cisco is the IP/VC 3540, which is a highly scalable multiparticipant videoconferencing
solution.The 3540 is targeted toward the large enterprise environments,
whereas, the 3510 is targeted to the low-end market.The IP/VC 3540 family of
products consists of a 3544 chassis, system module, MCU module, and application
server (AS) module, while the 3544 chassis has four slots with one required for a
system module and three designated for the other modules.The 3540 MCU is
available in three models: 30-, 60-, and 100-user types for system and nonsystems
modules.The MCM is part of Cisco IOS software, which runs on the Cisco
2500, 2600, 3600, 3810, and 7200 Series routers.The MCM function is to serve
as the videoconferencing gatekeeper and proxy.
Considering what’s been discussed in this chapter, you should now have a
greater understanding of the role gateway selection will have in developing your
ongoing enterprise solutions strategies, whether the importance lay in voice,
video, or both.