Cisco Certification: Introduction To ISDN, Part I

Telepresence and Holography / Holograms - November 2008

Editor’s viewpoint on their differences, likenesses and future...

We all just recently viewed an historic CNN holographic interview on an historic Election Night. CNN stated this type of imaging has never been done before on National TV and I believe that. I haven’t seen anything like it. The live interview caught me by surprise and sure had the “wow” factor attached to it didn’t it? Here’s a link to the actual interview.

CNN Hologram Video

The question now has to be asked. Is it Telepresence?

I’m no expert on the subject but I’m going to throw my hat into the ring, go out on a limb and say yes, I believe it is. Although I know many video conferencing purists are rolling their eyes and grabbing their guns right about now with my statement.

While I do know that Telepresence still hasn’t been universally defined (Houston, we have a problem), here’s how I see it…. Broken down to its simplest form - “tele” (through electronic means) and “presence” (present). This is how I’m justifying my opinion by lumping holography and Telepresence together. Just as Telepresence is surely an offshoot of video conferencing, holographic imaging (like we viewed on CNN) surely has to be considered an offshoot of Telepresence. The interviewer was “telepresent” from Chicago and beamed into the CNN Election Headquarters. She was most assuredly - “telepresent”. There was negligible latency, the imaging was fantastic and both interviewers were rehearsed on what they would say. I’ve just recently read that CNN actually “downgraded” the experience to make it “movie” quality and not as good as it could have been. Maybe they thought us mere mortals would be shocked if they showed their complete hand. I have a feeling it was so big to them, they didn’t want it to get upstaged by the historic election. I’m willing to bet we’ll see the “true” power of this technology in the upcoming weeks and months when they can put the pedal to the medal and show it off without having it sidetracked.

What an amazing time for this technology (all differences and opinions aside). Telepresence Doctors, nurses, teachers, schools and healthcare (healthpresence) will benefit from the recent gains in this state-of-the-art industry whether holograms, Telepresence or holography. Airlines also have to see the threat to a portion of their business travel. Hell, who wants go through security and fly to Miami for a two-hour conference when you can look them in the eye via Telepresence?

Beam me up Scotty! Simply amazing…!

Visit the free Telepresence Forum for more information and discussion

Your Editor and Administrator - L II
"Ride on the Next Plane of Existence" TM

From the CCNA to the CCIE, ISDN is one of the most important technolgies you'll work with. It's also very common in the field; ISDN is frequently used as a backup connection in case an organization's Frame Relay connections go down. Therefore, it's important to know ISDN basics not only for your particular exam, but for job success.

ISDN is used between two Cisco routers that have BRI or PRI interfaces. Basically, with ISDN one of the routers places a phone call to the other router. It is vital to understand not only what causes one router to dial another, but what makes the link go down.

Why? Since ISDN is basically a phone call from one router to another, you're getting billed for that phone call -- by the minute. If one of your routers dials another, and never hangs up, the connection can theoretically last for days or weeks. The network manager then receives an astronomical phone bill, which leads to bad things for everyone involved!

Cisco routers use the concept of interesting traffic to decide when one router should call another. By default, there is no interesting traffic, so if you don't define any, the routers will never call each other.

Interesting traffic is defined with the dialer-list command. This command offers many options, so you can tie interesting traffic down not only to what protocols can bring the link up, but what the source, destination, or even port number must be for the line to come up.

One common misconception occurs once that link is up. Interesting traffic is required to bring the link up, but by default, any traffic can then cross the ISDN link.

What makes the link come down? Again, the concept of interesting traffic is used. Cisco routers have an idle-timeout setting for their dialup interfaces. If interesting traffic does not cross the link for the amount of time specified by the idle-timeout, the link comes down.

To summarize: Interesting traffic brings the link up; by default, any traffic can cross the link once it's up; a lack of interesting traffic is what brings the link down.

In Part II of this tutorial, we'll take a look at some common scenarios that make the ISDN link stay up, and what can be done about it.

Chris Bryant Cisco Certified Internetwork Expert #12933

Chris Bryant, CCIE (TM) #12933, has been active in the Cisco certification community for years. He has written several books that have helped CCNA candidates around the world achieve the coveted CCNA certification, including several concentrating on binary math conversions and subnetting questions that the average CCNA candidate will need to answer on their CCNA exams.

He is the owner of The Bryant Advantage (http://www.thebryantadvantage.com) where he teaches affordable world-class CCNA courses via the Internet, and sells his popular Cisco certification books. He's proud to have helped CCNA candidates around the world achieve their career goals. Mr. Bryant's books and courses are sold on his site, on eBay, and on several other major Cisco certification sites.

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To learn more about Telepresence, the revolutionary new style of immersive video conferencing; visit these websites:

Telepresence - "Ride on the Next Plane of Existence" - Telepresence
Telepresence Web Portal - Telepresence Internet web portal
Telepresence Report - 24/7 breaking Telepresence related news and information
Via Telepresence - Video conferencing via Telepresence
Telepresence Forum - Free user discussion forum for everything Telepresence related
Telepresence Today - Telepresence information and editor qualified headline news
Telepresence Resource Directory - Telepresence web resource directory
Telepresence Tube - Telepresence videos, pictures and more