Skype: Telepresence for the masses

Video conferencing accounted for 28 percent of all Skype calls last year. Michael Kassner discusses why Skype should be considered a telepresence platform and how the multimedia technology of Skype has improved.

Michael KassnerLast week, I wrote an article called "Cisco's TelePresence: Not your average virtual meeting," hoping to acquaint everyone with technology that's dramatically changing business communications. After reading the article, a friend of mine (I punish him that way) mentioned that it's too bad telepresence platforms are so complicated and costly, as he'd like to use the technology himself. I found that statement somewhat surprising. I even had an "ah ha!" moment, which resulted in this article about Skype — as that's exactly what it does — provide a form of telepresence.

First the basics

Before describing Skype's use as a telepresence technology, it might help to explain exactly what Skype is and layout some of its history. Skype is a software emulator that allows you to use your computer, smart phone, or PDA to make telephone calls via the Internet. Skype's first beta (voice-only) came out in 2003. With Skype introducing their video conferencing application in early 2006 as Webcams were finally were becoming ubiquitous. In order to do this, Skype takes the Voice over Internet Protocol (VoIP) standard and alters it to meet its needs. Taking the high-level view, VoIP involves three steps to prepare the traffic for network transmission and the reverse to return the traffic back to an usable analog signal:

Digitizing the audio signals, or turning analog sound waves into 0's and 1's. Compressing the digital data using audio signal processing, otherwise the amount of transmitted data would paralyze the network. Encapsulating the digital information into a usable format for transmitting over packet switched networks such as the Internet.

Since the now digitized, compressed, and encapsulated data stream travels over the Internet, security and integrity of the digital information are of utmost importance. So let's look at how Skype handles that.

Authenticate and encrypt

Fortunately, Skype has taken care of information security in a big way. In fact, there's serious debate going on as to whether Skype methodology is too secure. Meaning the .govs aren't able to crack the data streams. Bruce Schneier (hero of mine) has a blog post called "VoIP Encryption" that gives an in-depth look at the whole process.

Skype security as in most network applications is a two-part process. During initial client setup, the Skype server issues each user a digital (1536 or 2048-bit RSA) certificate which will be used to verify identity. From then on at each log on, the Skype client sends that certificate's information back to the Skype server asking for verification. This initial authentication handshake should give everyone on the call a good feeling that the other parties are who they say they are, eliminating impersonation. This is critical, especially if you're not intimately familiar with the other party. Also a good reason to use video conferencing.

Secondly, Skype uses Advanced Encryption Standard (AES) 256-bit symmetric key encryption, allowing for a possible 1.1 x 1077 keys. That's a bunch and they're used to encrypt the data in each Skype call or Instant Message (IM). In order to securely transfer the symmetric keys between the individual Skype clients, Skype uses 1024 bit RSA public/private keys.

Skype's features (free)

Skype has all the features of a normal telco application. What makes Skype special is that it's free if the call is in-network (Skype-to-Skype). Simply put, anyone that makes international calls to friends or relatives should be using Skype. Just think no international calling charges. Other in-network features are IM, call recording, file transfer and conference calls. My favorite feature is video conferencing as it personalizes the conversation and is just plain cool.

Skype's features (cost)

For a nominal additional charge Skype offers add-on services that allow the user to transition to traditional telco networks:

SkypeIn: The feature activates a phone number that regular PSTN phones and cell phones can access. Automatically forwarding the call to the Skype client associated with the SkypeIn number. SkypeOut: Allows the user to call regular PSTN phones and cell phones anywhere in the world at very low rates, ($.02) per minute. As an aside, this feature is not needed if you're going to call toll-free numbers, that works and is free with the basic package.

So that's what Skype is, an Internet based telecommunications platform that mimics normal PSTN and cellular networks. Now back to whether Skype is a viable telepresence technology or not.

Is Skype telepresence technology?

It sure is. Surprised? Telepresence as defined by Wikipedia:

"Telepresence refers to a set of technologies which allow a person to feel as if they were present, to give the appearance that they were present, or to have an effect, at a location other than their true location.

Telepresence is a matter of degree. Rarely will a telepresence system provide such comprehensive and convincing stimuli that the user perceives no differences from actual presence. The user may set aside such differences, depending on the application."

I'm sure most people don't consider Skype or other video-ready IM applications a form of telepresence. They are according to Wikipedia, with Skype fast becoming the visual networking (industry-coined term for telepresence) application of choice among consumers.

Realizing that more people use video, Skype is working hard to create telepresence-quality connections. I realize that it's not remotely on par with Cisco's TelePresence suite, but with Skype's latest client software, approved webcam, and enough bandwidth the results are more than adequate. Let's look at each of these points and see what's required:

High Quality Video: Skype version 3.8 and Skype beta 4.o have incorporated what Skype calls High Quality Video (HQV). Skype's standard video offered a resolution of 320 x 240 pixels (QVGA) at 15 fps. Whereas HQV offers 640 x 480 pixels (VGA) at up to 30 fps. Simply put, video resolution is four times better and the frame rate is twice the speed, meaning a much sharper image and if so desired the ability to use a larger window, without losing image quality. HQV video Webcam: Skype has worked directly with Logitech to create optimized cameras for HQV. The specific cameras are Logitech QuickCam Pro for Notebooks, the Logitech QuickCam Pro 9000, and the Logitech QuickCam Sphere AF (Logitech QuickCam Orbit AF in the US). Bandwidth: HQV requires a symmetrical bandwidth of at least 384 Kbps. That may be a problem for some DSL users as the upload on many DSL circuits is only 256 kbps. The other challenge is that all parties have to meet this requirement, since it's symmetrical. Sorry, but that's the only way it'll work.

Skype mentions the need of a Dual-Core processor in the computer used for the Skype client. I agree that the processing requirements seem to indicate the need for Dual-Core. I've personally been impressed with computers using less powerful processors and would not hesitate to use them.

One final note, using good lighting, microphone, and speakers will go along way to add realism to the video conference aka telepresence experience. There are two more characteristics of Skype that need to be discussed. Doing so will allow you to make an informed decision on whether they're deal-breakers or not.

Possible issues

The first issue is Skype's proprietary software. This means it can't be inspected for weaknesses or back doors. Back doors are scary in that hackers or less than honest governments can exploit them to listen in on anyone's phone conversation. To quote Bruce Schneier:

"In the cryptography world, we consider open source necessary for good security; we have for decades."

My second concern is one of those double-edged swords. If you remember, most telepresence applications require significant bandwidth (5 Mbps per display) in order to provide the required realism. Skype has a requirement for 384 Kbps up and down. I realize that Skype calls are not pushing anywhere near the data that a high-end telepresence suite would, but that still doesn't quite explain the high bandwidth tolerance of Skype connections. That's until you realize Skype uses Peer to Peer (P2P) technology. P2P means that the entire network is a mesh of interconnected PCs. This does provide two important benefits for Skype users. A P2P mesh scales easily and will not run out of resources as they're shared by the individual components.

Now to the dark-side of P2P, computers are called nodes in a P2P mesh. Skype networks also use "super nodes" which are nodes chosen by the Skype servers to take on more administrative activities, controlling the P2P nodes in their immediate area. Since Skype software is proprietary, it's not publicly known how this works. One can only guess that there must be some kind of algorithm that determines if a node is a good candidate for P2P "super node". If your computer is chosen to be a "super node" it will be active if the Skype client is enabled, regardless if you're making a Skype call or not. It really boils down to whether or not you're comfortable with Skype using your Internet connection.

To understand this further I ran some tests and captured different screen shots showing firewall activity. The first image is with the Skype client disabled.

< ![endif]—>skype1.JPG

As you can see, there's very little activity. The next image depicts the activity seen by the firewall when the Skype client is enabled.

< ![endif]—>skype6.JPG

It's not a significant increase, but something people considering using Skype should know about. For more information, directly from Skype, please check out "P2P Telephony Explained-For Geeks only". The last image publishes all of the additional binaries that are affecting the firewall when Skype is enabled.

< ![endif]—>skype51.JPG

Final thoughts

All said and done, I like Skype and its capabilities. My sister is ecstatic about Skype. She called me one day not knowing what to do. Her eldest son was off to Spain for a full semester as an exchange student. She checked out some international cell phone plans and they were way more than what she wanted to pay. I mentioned Skype and it became the perfect solution in her case, keeping mom and son happy, except when he started growing a beard; remember, Skype has video.

I'm running the beta 4.0 version now and the quality is impressive. I still can't believe that cheap notebook speakers sound so much better than my smart phone. Sorry Samsung.


Michael Kassner has been involved with wireless communications for 40 plus years, starting with amateur radio (K0PBX), and now as a network field engineer and independent wireless consultant. Current certifications include Cisco ESTQ Field Engineer, CWNA, and CWSP.


Information is my field...Writing is my passion...Coupling the two is my mission.

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