Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Announcements

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Synchronous vs. Asynchronous link.

Synchronous vs. Asynchronous link. What are they? How they are different? Is synchronous always better than asynchronous link? Do I need to choose which one I want to use? Or it depends on link type? Ex. Dial-up and ISDN are synchronous?

4 REPLIES
Hall of Fame Super Bronze

Re: Synchronous vs. Asynchronous link.

The difference between the two, it's that one transmit and receive at the same speed (Synchronous) while the other transmit and receive at different speeds (Asynchronous).

Synchronous is better but it comes with a price. Asynchronous allows you to purchase more bandwidth for the money at the expense of lower upload speeds.

Dial-Up and ISDN are Synchronous.

ADSL is Asynchronous.

Silver

Re: Synchronous vs. Asynchronous link.

I am sorry but ADSL is not Asyncronous. It is syncronous and stands for Asymetrical DSL. It means that the download speed is larger then the upload speed. Sycronous means that the clocking of the data is transmitted with the data. Asyncronous the clocking mechanisms are independant at both ends. Asyncronous data has a start stop and parity bit in its data word. Syncronous works well with the high speed data protocols such as HDLC, PPP,SDLC,SONET etc.. Async is predominantly used for lower speeds....

New Member

I know you posted this 8

I know you posted this 8 years ago but thanks... it really helped make sense of the Syncronous/Asynchronous question... learning that protocols and encapsulation all involve what the packets and frames tell about the speed it wants to travel across Layer1 from one end to the other... how much data it's carrying, ack bits and how the next sequence is calculated into the headers... all of it... it's so much to learn and having an answer like that fits into what we're learning about the bigger picture so thanks.

Super Bronze

DisclaimerThe Author of this

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

BTW, you might also want to know, synchronous generally uses less bandwidth to transmit data than asynchronous.  You might also want to know when we talk of link "speed", it's really bandwidth, or capacity.  I.e. how much data we can move in some unit of time; not quite the same as how quickly it will arrive.  This distinction is important when dealing with long distance links, i.e. increasing bandwidth ("speed") often offers little improvement for applications being impacted by distance based latency.

7999
Views
5
Helpful
4
Replies
CreatePlease login to create content