Good point, but it is my understanding that with a well behaved TCP/IP
stack the flow control is handled end to end on TCP traffic, so if it is
just the last hop (AP to CPE) that is 'dropping' packets the rate is
backed up stream so the sender will not continue to slam your
connection, the backoff is across the whole virtual pipe.
Now, if you have a poorly behaving TCP/IP stack this will not hold true,
but you should only see this on an ancient windows machine and it would
only show in the customer trying to upload.
Sam Tetherow
Sandhills Wireless
Rich Comroe wrote:
My precious!
It further occurs to me that even if you have radio built-in bw management you
would also be pretty smart to have bw management enabled at the head-end, too.
Why? Radio built-in bw management will block customer excess rate inbound customer
traffic from wasting your rf capacity between CPE & Access Point, but if you've
got rf backhaul to the site you need head-end bw management as well to block excess
rate outbound customer traffic from wasting the rf backhaul bw before it ever
reaches the AP's outbound bw management. And the outbound bw is typically greater
than the inbound bw anyway. So it now looks prudent to me to have BOTH bw
management built into the radios, AND at the head-end.
Rich
----- Original Message -----
From: Jason
To: WISPA General List
Sent: Thursday, January 25, 2007 2:31 PM
Subject: Re: [WISPA] Advanced Bandwidth Management
From what I understand, there are many types of qdisc (HTB, CBQ, Prio,
on and on) that you can invoke with the 'tc' linux command. HTB is the
'Hierarchical Token Bucket' that you hear a lot about because it works
well. HTB should not be confused with 'Hierarchical TOLKIEN Bucket'
that has something to do with the Lord of the Rings. 'Leaky Bucket' is
a reference to my brains as I try to grasp bandwidth shaping.
Jason
Rich Comroe wrote:
> Great reference and I've learned a tremendous amount from this list. I
learned that I have been mis-using the term Leaky Bucket. I now understand that
what Jason described to the list is Token Bucket (I was totally wet in my earlier
reply calling it Leaky Bucket).
>
> Radios that implement bw management vary considerably in sophistication of
their bw management algorithms. I'm really impressed with the Alvarion bw
management. Canopy has bw management built-in as well, but it seems less
sophisticated. I'm also impressed with what I've learned Linux advanced bw
management can do at the head-end if your radios don't.
>
> Given radios can be bridged or not, bw management in the in-radio
implementations seem better ... because I don't see how head-end bw management can
distinguish between bw to multiple destinations behind the same customer radio if
the radios are bridged. Even if the radios are not bridged, then I'd see in-radio
bw management as 'still' better because bw limited at the customer radio doesn't
chew up inbound rf capacity, while in head-end bw management the rf inbound
capacity gets burned whether the traffic is ultimately limited or not.
>
> Anyways, I'm getting a great deal from the discussion, and would love to
hear if other radios have built-in bw management and what method is use for
comparison (any Trango users who could possibly comment?).
>
> Rich
> From: Ryan Langseth
> To: WISPA General List
> Sent: Thursday, January 25, 2007 12:44 AM
> Subject: Re: [WISPA] Advanced Bandwidth Management
>
>
>
> On Jan 24, 2007, at 8:25 PM, Rich Comroe wrote:
>
> > Thanks much. I love it when you talk technical! Sorry, couldn't
> > help it...
> >
> > No really, the devil is always in the details in these things.
> > This is just the detail I was looking for. After I digest I hope I
> > may send questions your way off-list. Still hoping operators using
> > other brands will share what bw management algorithms they may have
> > built-in.
> >
> If you are looking for a better understanding of some of the traffic
> control systems, the Linux Advanced Routing and Traffic Control
> manual is a good place to look. Starting at chapter 9, it goes into
> some detail on how some of the the algorithms available work and how
> to implement them.
>
> http://lartc.org
> http://lartc.org/howto/lartc.qdisc.html
>
> > thanks again,
> > Rich
>
>
> -Ryan
>
> --
> InvisiMax
> Ryan Langseth
> Systems Administrator
> [EMAIL PROTECTED]
> work: (218) 745-6030
>
>
>
>
>
>
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