Re: (no subject)
Re: (no subject)
- Subject: Re: (no subject)
- From: "Peter Sichel" <email@hidden>
- Date: Thu, 21 Jun 2007 10:26:08 -0400
On 6/20/07, Mike Gargano wrote:
> Let's say that I have 2 PPP dial-up connections (so I have two ppp
>interfaces created). If the two remote machines I'm connected to
>both have their default configurations and both are giving me back
>the same gateway IP and host IP for me to use, the only way for me to
>distinguish between the two is by the ppp interface. Is there a way
>using sockets or some other API to direct traffic down one of these
>interfaces explicitly?
No. Routing in TCP/IP is based on the destination IP address.
In Mac OS X specifically, one of these interfaces will be
listed first or higher up in the network service order
(as listed in the Network Preferences Panel). The router
associated with that interface will become the default
route or gateway. If the both list the same router address,
the behavior is not well defined, but the first one see
will likely be used.
I'm the developer of a NKE based product that allows you
to specify alternate routing criteria. For example, you
can look at which physical link a connection request arrived
on and respond via that link, or specify that traffic originating
from a particular service port should use one physical data link
or the other.
My NKE does this by first classifying the traffic based on
rules the user specifies, and then explicitly injecting
matching packets to the data link the user specified.
As you shift packets from one data link to another
("lateral put") at the interface filter layer, you
may need to rewrite the packets source IP address
and source MAC address to insure responses will be
received correctly.
Getting all of this to work correctly is not insubstantial,
but there are some interesting applications including
"load balancing" and "automatic failover". You can read
more about what I've done here:
<http://www.sustworks.com/site/prod_ipnrx_help/html/AlternateRouteHelp.html>
Beyond the technical bits, the user interface is another key
element, and one where my implementation could benefit from
more attention :-)
> Basically I'm looking for some way to
>multiplex the same destination and source IP address over two
>different interfaces.
Is there any reason why the network addresses need to be the same
across multiple interfaces?
At the most basic level, an IP interface is a data structure specifying
various interface attributes like an IP address and mask and some code
for handling messages associated with that structure. What's significant
is that an interface defines a protocol, a set of messages that we're
interested in, and some code for processing them.
Kind Regards,
- Peter Sichel
Sustainable Softworks
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| | >(no subject) (From: Mike Gargano <email@hidden>) |