Multilink

[Gerald Combs]

Paul Taylor wrote:

> As long as both end points of the PPP connection support Multiplink PPP
> you can use "bandwidth bonding".
> 
> Most major ISPs support the service (because the carrier modem banks they
> lease from support it).

...and because it's covered by an RFC (1990), which increases your 
chances for interoperability somewhat.  Multilink PPP adds an extra 12 
or 24 bit sequence number and some flags to the standard PPP header. 
This allows the connections to be (de)multiplexed and it's why both ends 
MUST support it in order for it to work.  We used it at a previous job 
for ISDN clients.  We're using it where I currently work to bond two T1s 
together into a single 3 Mbps "circuit."

BTW, it's also possible to use multiple _devices_ at each end with 
multichassis multilink PPP (Cisco) or RFC 2701 Multi-link Multi-node PPP 
(Nortel and possibly everyone else).

> I did a little testing with this. Testing with a 14.4kbps wireless phone
> and 56k dial-up connection , two 14.4kbps, and two PCS Vision phones
> (bursting was 290+kbps!) using Multilink PPP.

There's a practical limit to this.  The more connections you multiplex 
the more buffers have to be maintained at each end which increases the 
chances of things going all wonky, especially for dissimilar links. 
That's still pretty cool, though.