Forum

I'm studying for the CWNA and I'm reading CWNA 4th edition study guide. I just got done reading Chapter 5 and one of the review questions has me confused.

The question is pretty simple. Question #5 page 230.

What is the ID of an ESS?
A. BSSID
B. SSID
C. ESSID
D. It doesn't exist.

The questions answers state the answer is D "It doesn't exist" I answered B SSID.

Earlier in the Chapter it even says "The ESS has an ID too, which is the SSID."

Is this just a mistake in the book or am I missing something here?

ESS stands for Extended Service Set, considered a superset of BSS.
ESS is when you have multiple APs sharing the same SSID. This feature allows for roaming support.

For ex: Assume, you have a large hall, and you want to provide wireless coverage. One AP might not do the job, so what you do is place several APs, all using the same SSID, and at the same time the APs must all be connected to the same network backbone in order to handle users smoothly from one AP to another. Since all the APs share the same SSID and are able to communicate with each other on the wired backbone, they now form an ESS.

So, in response to your question: There is no specific id for ESS. It is simply the same SSID for all APs that will participate in the ESS.

Here is a small definition to help you:
BSSID: MAC address of the AP.
SSID: identifier that identifies a wireless network. (edited)
ESSID: no such thing -- although all APs in ESS share the same SSID.

Btw, I also studied in the official CWNA guide. You should:
- Download the book's errata and correct all the mistakes that are in the book.
- if there is anything you don't fully understand in the book, I suggest you google it and/or wiki it since the CWNA book has lots of missing info that are crucial for the exam.

Kerric Escribi?3:

BSSID: MAC address of the AP.
SSID: unique identifier that identifies a wireless network.
ESSID: no such thing -- although all APs in ESS share the same SSID.

The BSSID up there is the Unique identifier.

SSID` need not be unique.

vivek2727 Escribi?3:

Kerric Escribi?3:

BSSID: MAC address of the AP.
SSID: unique identifier that identifies a wireless network.
ESSID: no such thing -- although all APs in ESS share the same SSID.

The BSSID up there is the Unique identifier.

SSID` need not be unique.

1- I meant unique in case he wants to have multiple SSID, each SSID should be unique.
2- BSSID is unique on an AP basis. True...It's the AP MAC address.

Ok, so the SSID could be considered the ID of the ESS but it's not an official ID of the ESS?
Interesting.....

slickwilly Escribi?3:

Ok, so the SSID could be considered the ID of the ESS but it's not an official ID of the ESS?
Interesting.....

AND

slickwilly Escribi?3:

The questions answers state the answer is D "It doesn't exist" I answered B SSID.

Earlier in the Chapter it even says "The ESS has an ID too, which is the SSID."

Basically, The ID of the ESS is the SSID shared among all APs in that ESS.
Now what the book mentioned is the same as above, i.e: no such thing as ESSID. But I wonder if you got such a question on the exam what will the correct answer be, since unfortunately there are a lot of misconceptions in the Wireless terminology.

But I wonder if you got such a question on the exam what will the correct answer be, since unfortunately there are a lot of misconceptions in the Wireless terminology.

I was wondering the same thing.

When in doubt, I always go to the standards for clarification. I hope this helps.

ESSID is not mentioned in the 1999 802.11 standard, not even as an acronym.

3.7 basic service set (BSS):
A set of stations controlled by a single coordination function.

3.25 extended service set (ESS):
A set of one or more interconnected basic service sets (BSSs) and integrated local area networks (LANs) that appears as a single BSS to the logical link control layer at any station associated with one of those BSSs.

3.20 distribution system (DS):
A system used to interconnect a set of basic service sets (BSSs) and integrated local area networks (LANs) to create an extended service set (ESS).

I had that same question when I first started. The only wireless experience I had was on Windows and Linux, and the 'iwconfig' command using 'essid' gave me the impression that 'essid' was a real term from the 802.11 standard (which it isn't).

Just stick to the basics -- BSS, ESS, and DS. All else is fluff!

(While I don't have a CWNA, I appreciate the training material and forums, as they've helped me blow away some of the cobwebs in my thinking on various wireless things!)

IMHO - several years ago, some companies misunderstood the meaning of ESS and started using the nonsense term ESSID. They continued using it, and now ESSID is used in hundreds of their manuals and documents.
Rather than explain to their VARS and customers that they were ignorant (originally) they continue using ESSID when they should have used SSID all along.