Ascend Archive
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Re: (ASCEND) Bonded T1's?
At 05:16 PM 1/5/98 -0800, Peter Lalor wrote:
>>From: Matt Holdrege <matt@ascend.com>
>>
>>At 10:52 AM 12/30/97 -0600, Scott Kozicki wrote:
>>>Can you bond multiple T1 interfaces together on a Max 4K? That is to
>>>say, can I MPP 2 T1's together to form one ~3MB pipe upstream?
>>
>>Well, you can bundle multiple channels across T1's, but you can't bundle
>>two unchannelized T1's together.
>>
>>However, beware that vanilla TCP/IP doesn't work well at all when you
>>exceed about 6 to 8 MP channels.
>
>Like Ethernet? ;-) Can you define "vanilla" in more detail? Is there an
>inherent problem in IP, or is it a question of tuning?
Vanilla meaning non-altered. The way TCP works with window sizes and acks,
etc., doesn't perform well over MP of you have a lot of channels. You send
data, you get an ack. That means you have to wait for the ack rather than
sending more data down another channel. But there are alternative proposals
and experimental alterations to TCP to make it perform better in this
scenario.
>>At 09:24 AM 12/31/97 -0600, Joe Shaw wrote:
>>>That's more of a kludgey solution. Any sensible person wanting to bond
>>>T1s needs to purchase an inverse multiplexer. Larscom has some nice units
>>>that scale from 1 to 4 T1s and work well, but they aren't cheap. They are
>>>easy to setup and work quite well. Of course, if you've got channelized
>>>T1s, I'm sure it's possible, but it just doesn't seem like a good idea,
>>>unless you really want to try it.
>>>
>>>Advertising one set of routes via one T1 and then another set of routes
>>>is a bad idea. If one goes down, so does half of your network. I'd
>>>rather use an inverse mux and a dedicated router doing BGP than say
>>>rip/ospf over serial links into a max.
>>
>>If one T1 goes down, the routes will move over to the other T1 if you
>>configure the router properly. BGP is not required, OSPF will work fine.
>>
>>But yes, an imux will work much better than Multilink PPP.
>
>Again, would you mind being more specific than "much better than"? I
>imagine it's usually preferable to use hardware when possible for various
>reasons, but what are you thinking of specifically?
An imux works at lower layers so higher layer protocols like TCP are
unaware of the fact that you have multiple channels.
Matt Holdrege http://www.ascend.com matt@ascend.com
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