As far as the issue of bandwidth versus QoS, QoS in the endpoints and the
critical requirements of communications to/from anywhere on the Net should
enable the making of informed decisions when investing in quality for voice
communications. QoS is, however, not only required for interactive voice com-
munications but also for video, as video becomes more prevalent on both
wired and wireless SIP-based communications. 4G wireless networks espe-
cially will be able to support interactive video right from the start. It is useful
to note that video codecs are more sensitive to packet loss: Synchronization
mechanisms are annoyingly visible during resynchronization after large
dropouts. In the following material, we will, however, discuss only QoS
required for voice, since there is ample experience in the industry with it,
while video seems to be an emergent application that so far has not received
the same scrutiny as voice.302 Chapter 18
MR. QOS VS. MR. BANDWIDTH
The topic of providing bandwidth vs. deploying network equipment for QoS is
much debated in technical forums and trade journals [1].
This chapter should help our readers navigate safely through the rocks of
commercial pressure to buy QoS hardware, software, and whole QoS network
solutions (the more costly, the more enjoyable to the vendors in the QoS
industry niche for VoIP).
A short reality check will reveal that all commercial VoIP service providers,
including former telephone companies or the giant IM and voice services such
as AOL, Google, MSN, Skype, or Yahoo!, work quite well without QoS, since no
one can control VoIP calls end-to-end between arbitrary points on the Internet.
Also, Skype, Google, and others have proven with massive deployments in the
market that quality for voice is mostly an endpoint property, as long as the path
over the network does not suffer from plain congestion. Voice traffic is a
negligible fraction of the Internet traffic and hardly contributes to network
congestion.
The authors have conducted most of their telephone conversations for years
over the Internet to enjoy the better-than-PSTN conference quality sound using
our computers or SIP desktop phones.
As for IP PBX and IT network vendors arguing the case for expensive QoS
equipment, remember that customers and business partnerswill never
experience any of the presumed quality if it exists only inside their private
network. It is hard to present an adequate business rationale for providing QoS
inside private networks only.