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

Structured and Unstrctured DS1

Hi Champs,

Want to clear some doubts ;)

Thre is a terminology Unstructured DS1

and Structured DS1 which is further divided into Channelize and unchannelized

I understand Unstructured DS1 is that a single pipe will be used but when it is structured channelize we can break the pipe to DS0 level but what I am not understanding is Structured unchannelize?

I will highly appreciate if you can throw some light on this.

With Regards,



Re: Structured and Unstrctured DS1


the first question for me is, where you did pick up the terminology?

I think you understood correctly, what structured vs. unstructured means. In the structured case you can group contiguous DS0s to a logical interface.

You can also group all DS0s into one interface, maybe this is meant by the term "structured unchannelized". I have to admit that I met the term first time in your post.

In any case there are some informations about T1s found at

Hope this helps! Please rate all posts.

Regards, Martin

Re: Structured and Unstrctured DS1

Hi Martin,

There is definetely some technical difference which I am not able to catch off.

Actually when we say structured unchannelized and we group all DS0 into one interface it is same as Unstructure?

WhY I am saying is when I am trying to configure data trnasfer type as UNSTRUCTURE the only option I get for INTERFACE TYPE is CE (Circuit Emulation).

But when I am trying to confiure data trnasfer type as STRUCTURE I get option for INTERFACE TYPE as UNI,CES,HDLC Passthrough and Framerelay UNI, ATM PNNI etc etc for both channelize and unchannelize.

Can you or someone explain me the logic behind?




Re: Structured and Unstrctured DS1

Hi Ankur,

I think the term 'unchannelized structured service' just refers to a service with one channel that uses up all the timeslots. In fact, if you look at the CES specification from the ATM Forum ('Circuit Emulation Service Interoperability Specification -

AF-SAA-0032.000') you will see that the very definition of a strucutred service is that it is as 'Structured DS1/E1 Nx64 Kbit/s Service' - there is no provision within that for unchannelized operation. However, it does allow for all 24 timeslots to be used to form a channel.

I don't think the issue is your understanding... the issue seems to be the meaning intended by the CLI of whatever system you are configuring.

Hope that helps.


Re: Structured and Unstrctured DS1


looking at an E1 the terms are more understandable (at least for me ;-).

Unchannelized E1 -> 2048 kbps bitstream - no DS0s

Channelized E1 -> 1984 kbps data rate, TS0 used for framing.

Both can be used to transport frame-relay or ATM cells in OSI layer2 as an example.

The terms in your last post probably refer to something different. I assume UNSTRUCTURED will just transport the bitstream of the interface - maybe not even looking for Byte boundaries and especially independant of Layer2.

STRUCTURE will look for structures in Layer2 like Frame-relay, ATM, etc. This is possible for an channelized or unchannelized E1 (see above). The confusion arises probably from the fact, that there are different structures in different OSI layers. In this sense STRUCTURE or UNSTRUCTURE are relating to Layer2 and not to the terms in Layer1 used for an E1 or T1. This view is also supported through the terms "channelized" and "unchannelized", which refer to Layer1 settings.

Hope this helps! Please rate all posts.

Regards, Martin

CreatePlease to create content