What is Permanent Virtual Access....
Permanent Virtual Access (PVA)
is an Internet Service Access model which defines a new 'Type' of connection to the
Internet (Intranet). PVA provides essentially
instantaneous, bi-directional, switched access to the Internet (or Intranet).
Today customers have the choice of dial-in or dedicated access to
the Internet (if you think xDSL is an escape you may want to check this out). This choice is based on historic concepts and the analog modem
paradigm and has little, if any relevance, to modern switched ISDN
networks. Using PVA ZyTrax contends that Internet access costs for higher speed services (64 to 512K) can be reduced
by up to 75% and for certain types of services even more. We provide 64K PVA access on our own Business Class ISP service for $70 p.m.
PVA provides the user with what appears
to be continuous access to the Internet (Intranet) while only maintaining connections when
data is actually being Transmitted in either direction.
We are simply applying the same principles that were applied to the voice telephone network after the introduction of the Strowager exchange in 1912. The effect of this is to
substantially reduce the capital and operational costs for the ISP or Intranet Operator
and thus lower the cost of service for the rest of us.
PVA permits numerous services innovations:
PVA and Dynamic Bandwidth
ZyTrax with HotPools™
offers ISDN access at speeds from 64 to 512K. Web sites, FTP sites and IP videoconferencing as well as classic
Web access are all examples of the need for dynamic bandwidth having, by their nature,
substantial or unpredictable peak-to-trough demands.
- HotPools™ enables each channel to be fixed or dynamic for you can have the best of all worlds.
PVA and Virtual Private Networking (VPN)
- VPN (the secure transmission of data over a public network) will be
incorporated into HotPools over the next few months. PVA, VPN and Dynamic Bandwidth ..
just think of the possible applications.
Instant E-mail
Voice Calls (or IP Videoconferencing)
Guess what, the network calls you if you are not currently connected (isn't that just a bit like the telephone network).
The list of potential new services is almost endless. Why
not send us mail with your ideas to pva@zytrax.com.
Definitions and explanations
...essentially instantaneous...
No point in pretending its instantaneous. Connection (in
either direction) can take as little as 700 ms if sensibly implemented. We've done a lot
of work on this topic. Call connection times vary here (in Montreal) from 0.5 sec. as a
low to 1.6 seconds as a high. Negotiation and Authentication of an MPPP connection will
take from a low of 200ms (in a well implemented system) to a high of over 2 -3 seconds in
a badly sized configuration when authentication uses a busy RADIUS server. ZyTrax
contends that the average start connection to data transmission should be in the range 0.7
to 1.8 seconds.
Contact us at pva@zytrax.com
if you have comments, suggestions, insights.
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....bi-directional...
Permanent Virtual Access is a bi-directional service.
Premise Routers will call the network or the network's Access Routers will call the user
based solely on the presence of traffic. All of this is automatic and fully authenticated
(using CHAP or PAP). Sound just a tad like the telephone network again.
About now the 'fatal flaw' seekers will be saying 'what
about measured service areas?'. Well what about reverse charging the customer for outbound
(from the Network) calls. The customer is already paying and is likely to pay a lot less
with PVA ...and the costs are directly proportional to traffic volume.
Contact us at pva@zytrax.com
if you have comments, suggestions, insights.
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...switched....
PVA uses the capabilities of the switched network.
Incoming calls go to a 'Pool' of lines (called a 'Hunt Group' in some places) where the
Network Access Routers pick them up. The service is inherently far more reliable than
current dedicated lines. With dedicated lines if the end equipment or the physical line goes down anywhere from you to the
ISP then your connection is out. With switched access you are only vulnerable to a local
loop fault (from you to your nearest CO).
Can you get busy signal? With proper engineering
the answer should be very, very rarely. Again, using the telephone analogy, did you know
that in most areas COs are engineered to allow only 10 to 30% of customers to use the
telephone at any time. Do you get a network busy signal.. very, very rarely.
Contact us at pva@zytrax.com
if you have comments, suggestions, insights.
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...ISDN...
Poor old ISDN has gotten itself a bad rap in North
America (though those fiendishly cunning Europeans seem to have got a handle on it). Fact
is, it was promoted as the solution to all problems (sound a bit like xDSL) which it is
not (sound a bit like xDSL).
Here is our view of ISDN.
Its ubiquitous NOW (none of
this '...if you can swing a dead cat and hit the CO you can get the service otherwise move
house' stuff).
ISDN is reliable (bit error rates are staggeringly low).
With ISDN you get
what you pay for, 64K or 128K or whatever (none of this '..with a following wind, downhill
you can get to 42K as long as its not raining' stuff).
ISDN's call set-up times are very, very fast. The dial time is fast and when you are
connected, man you are connected (none of that whining for two hours while the two ends
figure out if they can talk to each other and at what speed).
OK ISDN can be a bear to set
up if you get the wrong Telco on a bad day (though here in Canada, Bell don't have problems
any more ... now if you want something out of the ordinary...well!). Besides, how often do you install a
line (also checkout CoolFig, ZyTrax's GUI based configuration tool - we think we've done a pretty good job)
Contact us at isdn@zytrax.com
if you have comments, suggestions, insights.
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