Telecomguy,
Let's be clear...
but the fact is circuit switched calls are voice that has been packetized which is then routed via various
different transmission network technology (ATM, SONET, IP dare I say?) in the Carrier backbone.
Very few telephony networks use IP or ATM. Most circuit switches digitize the calls and use TDM (circuit) technology for call set up and tear down...thus the term circuit...distinctly different from "packet" which allocates frames (or cells) to a network on a packet by packet basis. ATM is cell based (switches cells), IP is packet based (switches or routes packets), circuit switches are circuit based (switches circuits).
The only issue is how the
bandwidth is managed --- i.e. in Circuit-Switched method, there is actually a guaranteed voice path and capacity established
from end-to-end to ensure certain level of quality but because that bandwidth is guaranteed and reserved, if two people are not
talking - like pauses -- that bandwidth is wasted so the Virtual Packet network approach which IP uses is more efficient in that
sense that if there is silence, no bandwidth is wasted since voice packets are sliced and sent via WHATEVER routing is available
-- BUT herein lies the problem -- because packets are routed wherever there is capacity all kinds of problems occur (latency,
packet loss, etc.) resulting in dropped calls, echoe, garbled metallic sound, etc.etc.
Partially rigth. Again circuit switches do not allocate bandwidth. The "circuit" is a permanent circuit which is established "permanently" for the call duration. In packet networks the call's are allocated on a per packet basis. ATM and IP can route calls through a backbone and pass different packets different directions based on congestion (trunk or node). Even with ATM PVC's this is the case. In circuit all the traffic follows a single call path once established. And yes, this packet by packet routing does create issues wrt latency and jitter...but you'll note that most of these issues have been solved with rtVBR on ATM and IP precedence, diff serv, RSVP, and other QoS mechanisms in IP. As for tinny "metallic" quality..this is codec issue - not an infrastrucutre issue. If you run PCM or ADPCM on an IP or ATM network the sound quality is the same as in circuit switched networks.
Once the Internet players ever figure out how to introduce QoS (Quality of Service) which will be very
difficult due to competing interest and the requirement to completely OVERHAUL a network
You haven't been paying attention to this QoS work. "overhaull then network" - you're talking about software.
The reason why some
Carriers are moving towards IP versus ATM is that there are certain application and deployment advantages in building IP
transmission based backbone network which I won't get into here.
Not too mention that IP - by virtue of the fact that it operates at above layer 2 - can offer a wide range of service (That translates into revenues for the carrier)that layer 2 circuit switching can never offer.
of course the problem is that if you are ONLY talking about PC-TO-PC market, you are only
talking about VERY small % of the total market -- who the hell wants to fire up their pc, load the Vocaltec software, buy hardware,
integrate it into their PC, and then make sure the person they are calling is ALSO available to take the call with all the proper
hardware/software
First this technology is converging very quickly. Second the PC is the softphone in your example - there is no hardware requirement. Third, your PC will come from the factor loaded with the "standard" client code. Worst case you'll be asked to download a "plug-in" or "driver". I know this all sounds difficult to you but it will be very easy very soon. Remember this conversation.
to by-pass the PTT, the Internet Telephony players would have to install and maintain gateway quality
switches in ALL major towns, cities and villages around the world.
Yes!!!! Big opportunity!!!
AND IT'S ILLEGAL IN
MOST COUNTRIES.
Acutally not anymore - most wired countries have deregulated or have plans to.
You can't simply start dropping PC servers in 100,000 local POP's --- this will take a long time and trillions of
dollars of capital.
Ajoining real-estate for the interim and yes lots of $$$$ being spent! That is the opportunity and carriers will be forced to play as small competitive carriers bring new unique services to market which rely on IP infrastructure. I think you underestimate the level to which deregulation has happened and how this will actually cause migration to occur faster than perhaps you believe. I still think you're in denial.
OG |
