My QoS Primer for Small Business Management
Sam C. Chan Feb 27, 2017
Digital communication is conducted by transmitting packets.
At the ISP & backbone level, packet prioritization is enforced at all
paths, according to their policies, objectives and obligations.
Some traffic receive preferential treatment, while others are delayed,
or even lost/rejected. They regulate the rate (speed), quota (amount), and type of traffic down to the most minute detail.
At the customer's premises, things are uncontrolled: no limits, nothing
discriminated, nothing blocked, pure FIFO (first in, first out) --unless IT
measures and apparatuses are in-place to enforce policies.
A typical Internet subscriber line is 90%~99% idle on
average, just like a typical workstation CPU is 99% idle over a 24-hour
period. Capacity allocation must consider the peak demand. The point
here is: bottleneck & contention, during those brief but critical
QoS (Quality of Service) is the computer science term for prioritizing packets, aka Traffic Shaping.
It is done by reserving, say, 10% of the available bandwidth, and give
it to designated priority packets, as a boost, thus
preventing critical applications (RDP, VPN business apps) with
light but urgent traffic from being starved by bulky auxiliary
applications (downloading, streaming, email attachments, etc.)
The result is a slight reduction in overall utilization efficiency
(more wasteful), because the line is never allowed to saturate. Such
added delay might
not even be discernible by those affected. On the other hand, the few
favored applications would see a very noticeable boost in responsiveness.
Within the gigabit LAN, bandwidth is abundant. Meaningful contention is practically a non-occurrence. WAN typically have outbound
bandwidth of 0.5~3.6 Mbps, for 99% of small businesses in the US.
That's only 1/2000th ~ 1/300th of LAN speed. Congestion and
show-stopping degradation is certain recurrence, begging for active control.
QoS implementation can range from basic to extremely sophisticated and
complex. It is not a miracle solution, as there are scenarios where
prioritization won't resolve issues, in which case it needs be
implemented in conjunction with other techniques. For most small
businesses, lack of QoS is without-a-doubt the
top bandwidth-related issue, and it's considered mandatory.
NOTE: This has been thru several revisions in the past 10 days. I
narrowed it down to absolutely essential points. Each point is condensed
into a single compound sentence.
Such technical concepts must be conveyed in a well-structured manner,
in strategic sequence. You need to reread it sevreal times. Once you
grasp the big picture, you're able to ask specific questions, and
comprehend the responses.