God help us.

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I'm reading the chapter on ISDN and boy, the amount acronyms and terminologies and aggravation-isms is giving me a headache. ITU this and DS0 that and Q.921 the other .....

Crikey !

Who the hell comes up with all of this stuff ?

 

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At least now I know what a Q921 is. Come exam day and they ask:

Examiner: what is a Q921 ?

Examinee: LAPD (Hey Presto !)

Examiner: Correct ! Well done.

Examiner: So what is an LAPD ?

Examinee: Los Angeles Police Department.

Examiner: Er, nope ! Sorry. I'm afraid you've failed your CCNA on this ocassion. Try again next year.

 

Gives you a 'headache' doesn't it!

 

Buddy I feel your pain!

It is a common problem in IT and Comms - and I type this in Oz at midnight... and yes I have a bad headache otherwise I would be asleep.

The acronyms are devised in part due to the RFC's or request for comments that august bodies like ieee [institute of electronic enginners] use to define a protocol, service or IT product.

Usually the naming and description of operations desrcibed by an RFC finds it's way into the end product - hence acronym city on some occasions.

With ISDN you just have to remeber that it is a managed service not a just a connection. Also if you understand basic rate and primary rate then you are well on your way.

ISDN explained...
http://www.broadcastisdn.net/isdn_explained.php?PHPSESSID=caaeec36229e113234815dab9377812e

ISDN explained by Cisco - relevant to your course and then some!
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/isdn.htm

HTH

supag33k

 

@simongrahamuk

Absolutely ! Headache is my name. And headache is my game (well, at least until I get to the end of this chapter, anyway.)

@ Supag33k

Thanks Buddy. Those links are a great help. Now if you have a couple of aspirins to spare, I'll be well on my way.

 

On the bright side ISDN probably will be out on the next version of the CCNA.

 

Not too many places seem to use it anymore.

 

dont most networks use an ISDN backup though? (I know we do lol)

 

We had a T1 connection and a Frame Relay backup at each site, but our applications required more bandwidth than even a T1 could handle, so we currently have four bonded T1s at each site at a minimum. We're probably going to get a business cable connection for a failover link.

 

Most of our facilities use at least two bonded t1s as primary and a metro ethernet connection as a backup.

We are moving to having the facilities route out primary through the metro E and use the t1s as backup.

We used to have 2 to 3 t1s as primary and a single t1 as secondary.

Remote sites usually have a single t1 link (doctor's offices, surgery centers and so on). Occasionally they have a t1 with a fractional t as a backup. Probably can burst over the CIR at an increased cost, but I feel this will go away.

 

In the UK we don't have T1s, and the equivalent, an E1, is too expensive when delivered as a leased line.

Consequentialy ISDN is heavily used by businesses, mostly as a backup for an ADSL connection.

The company I work for has a very popular package of ADSL, ISDN backup and a SLA.

Harry.

 

<giggle>

Actualy I found the difference between Q.921 and Q.931 easy - the first is layer 2, the second layer 3 (OSI layers).

Harry.