Two ISP lines

[Randall R. Stewart (home)]

Juan Rodriguez Hervella wrote:

>Just some questions about this paper:
>
>"(...) Note that this route has to be at the same level of the tree, i.e.
>the code cannot return a less specific match or a more specific
>match (...)"
>
>Question: I don't understand why if you are looking for an alternate
>route you aren't allowed to retrieve a more specific route. This doesn't
>make sense to me. If you are routing packets using a route when
>there is a more specific match, you aren't doing "longest prefix match".\
>
When you first ask for a route.. you get the longest prefix
match. So you are at say a depth in the tree of N. If you
try to go to a lower level in the tree (say N-1) then you
could be going to the wrong place... I suppose one could
go to a N+ level in the tree.. i.e. more specific match (assuming
that maybe a new route was added lower in the tree).. but I
never contemplated that aspect much because it would
be more of a corner case I think... It would also make
the code a bit more complex as well :->

>
>Another question: if ISP-1 goes down, and you use this feature of
>alternatives routes, this still doesn't fix the communication problem. Unless
>you make something with the source addr. of the multihomed site's
>packets, the reply packets will be lost in the faulty ISP, imho.
>
Ahh.. it is true that SOME ISP's do ingress filtering.. for TCP
this would be a problem.. But for SCTP (a multi-homed protcol)
this is NOT a problem.. the SCTP association would just
use the source address of the outbound interface (since the
association is made up of a SET of addresses on each side
and a port on each side)....

Now there are still ISP's that do NOT filter (I have one that
does and one that does not :->)...

R

>
>Regards.
>
>
>
>
>On Friday 23 January 2004 01:38, Randall R. Stewart (home) wrote:
>  
>
>>Andrea/all:
>>
>>An interesting question... the following link has
>>some thoughts along these lines... and something
>>for the BSD community to think upon...
>>
>>http://www.sctp.org/what_is_alt_route
>>
>>TCP could definetly use something like the above (with Itojun's Multi-path
>>updates as well).. it would give more reliability to  even a singly
>>homed protocol such as TCP :->
>>
>>R
>>
>>Andrea Venturoli wrote:
>>    
>>
>>>Ok, I asked already asked something similar to this in the past, but it's
>>>not the same thing... maybe it's a trivial question...
>>>If I had two lines to the Internet: how would I use both?
>>>Could I just provide two default routes? How?
>>>What algorithm would be used to choose among the two?
>>>What if one failed?
>>>
>>>bye & Thanks
>>>       av.
>>>
>>>
>>>
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>>>      
>>>
>
>  
>


-- 
Randall R. Stewart
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