It is worth noting that you lose the benefits of routing protocols when you
bridge your network

Sure, there's always RSTP... (heh)

Many larger wireless / Wifi based architecture these days seem to be
favoring a layer 3 tunneling / handoff method over a bridged layer 2 network


Technology Architects 

-----Original Message-----
Behalf Of Tom DeReggi
Sent: Monday, June 12, 2006 5:30 PM
To: WISPA General List
Subject: Re: [WISPA] looking for a device

To clarify....

The term I referred to as "Double VLAN" is not the technically correct name 
(thats just what I call it), it is actually called "Q in Q" as stated by 
several in this thread.

One of the reasons this is valuable is for a wholesale network. It basically

allows you to create a single VLAN end to end across your network for a 
subscriber or reseller, and still use VLAN for your local needs to operate 
your network.

I'll give an example of where I might use VLAN for my network need. I have a

single fiber connection from the basement to the roof.  On the roof I have a

VLAN switch and 6 sector radios. I have a router in the basement.  I could 
then seperate data between the different radio traffic by giving a unique 
VLAN to the Ethernet port that each sector radio connects to, and route 
between them in my basement router.

I'll give an example of where I'd use a VLAN end to end for a reseller. 
Reseller has a connection between me and them at one point on my network. 
The reseller might provide the backbone and IPs. The client routes the 
customers traffic to a specific VLAN when entering my network. I then have 
that VLAN configured across my network until reaches the end user's building

router that terminates the VLAN.

Now what happens when the resellers customer (example 2) resides in the 
building (example 1)?  Normally two VLANs can't exist simultaneously as teh 
switch wouldn;t know which ID to tag data with.  Q in Q VLAN would allow one

VLAN ID to reside in side of another VLAN.  Its the same concept as 
tunnelling, except for its not.

Now how does this apply to radios that support Q in Q? Depends. Use your 
imagination. The first problem is can the radio pass Q in Q VLAN data? 
Second can it tag it? Being able to tag VLAN data at the radio level can be 
extremely useful. First off it avoids having to configure a second device 
(VLAN switch) that complicates the automation of configurations.  Part of 
the Idea is that CLECs and Governement, are all high on Security, and they 
do not want to have to coordinate complex IP models between their systems 
and the wholesalers, instead they want to be able to send traffic LAyer2 and

seperate traffic so one client does not have the abilty to see the other 
client's traffic.  Its sort of an Ethernet way of doing a Private Virtual 

The only problem with VLAN is you need to have every component of you 
network that passes VLANs to be able to pass large packets so Full MTU can 
be delivered to clients. This is one of the limits to Wifi and regular 
switches, is many Wifi devices and all non managed switches do not pass 
large packets.

Radio like Trango and Alvarion (with Q in Q support) have the abilty to pass

large packets.

The other advantage of VLAN is that when used across a PtMP design and VLAN 
support at CPE, it allows doing remote banwdith management based on the 
customers circuit ID, and having a way to distinguish and differentiate the 

Q in Q, gives the provider flexibilty on how and when they would like to use

VLAN and in multiple ways simultaneously.

Its uncertain how Q in Q will be used for sure, as VLAN does add much 
complexity over say a basic bridged design.  Part of the benefit, is that 
redundancy is not always supported in an ideal way when VLAN is used. By 
allowing a VLAN end to end encapsulated in the other packets, it potentially

could allow avoiding the pitfalls that limit redundancy by having the end 
locations (the reseller and the client) the one tagging  the VLAN and 
knowing that that VLAN info survives any other VLAN tagging that may happen 
on the network, or for that matter abilty for that data to route across 
paths that are not technically that VLAN assignment on the other layer.  I'm

not explaining this clearly, but that is the gist of it.

The end result is, if a provider's whole network supports Q in Q, it allows 
them to compete with other fiber Metro-E services.

Many believe that the design of the future for Metro deployments is to run 
MPLS at the edge devices, and then Q in Q VLAN inside the Metro Ethernet 
rings.  The key ideas here is abilty to creaetequivelent of virtual circuits

of Ethernet.

Tom DeReggi
RapidDSL & Wireless, Inc
IntAirNet- Fixed Wireless Broadband

----- Original Message ----- 
From: "Charles Wu" <[EMAIL PROTECTED]>
To: "'WISPA General List'" <>
Sent: Friday, June 09, 2006 11:33 AM
Subject: RE: [WISPA] looking for a device

I think Jon is asking about the "double VLAN" -- or a "q in q"
implementation It's extremely useful for creating virtual bridged customer


Technology Architects

-----Original Message-----
Behalf Of Rick Harnish
Sent: Friday, June 09, 2006 9:10 AM
To: 'WISPA General List'
Subject: RE: [WISPA] looking for a device

Virtual LAN.  Imagine segregating segments of your network across a backhaul
pipe so that they flow together but don't actually see each other.  Managed
switches have the ability to create VLANs per port.  Think of it as a merger
between routing and switching.  Its a pipe or several inside a pipe.  Tried
to be simple here, I'm sure someone else can give you a more technical

Rick Harnish
OnlyInternet Broadband & Wireless, Inc.
260-827-2482 Office
260-307-4000 Cell
260-918-4340 VoIP

-----Original Message-----
Behalf Of John Scrivner
Sent: Friday, June 09, 2006 9:39 AM
To: WISPA General List
Subject: Re: [WISPA] looking for a device

Can you or someone explain what double VLAN is? I have never heard of such a
thing. How can it be used to help us? Thanks, Scriv

> Yo may want to look at Alvarion. Alvarion does support VLAN. new 
> Firmware4 supports double VLAN also. Alvarion used to have one model 
> that was designed to have a second integrated radio into it.
> I can't remember if it was a 900/2.4 combo, or a 5.8/2.4 combo.
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