Mike DeMaria
Notworking Computing

Broadband Internet access has hit an all time high.  Every day cable modem and
DSL providers receive hundreds of new members.  A growing concern in the
industry is that the Transmission Control Protocol has grown to be inefficient
for high speed Internet programs and as such newer protocols should be phased
into the IP stack.  In our Syracuse University Real World Labs, we recently
compared high speed applications over TCP and a newly implemented protocol,
Transmission of IP Datagrams on Avian Carriers (RFC 1149 - 
http://www.cis.ohio-state.edu/htbin/rfc/rfc1149.html).
  
IP Datagrams on Avian Carriers (IPDAC) was actually developed well before 
the Internet, back in World War II.  George Turing, brother in law to Alan 
Turing, hypothesized that a datagram could circumnavigate a network by 
stopping at locations that he called "data ponds".  In these ponds, 
datagrams could be analyzed to see if others were going to a common 
destination and send larger packets there, freeing up the carrier for the 
originator.

Our tests included maximum bandwidth transfer, fault tolerance, sustained 
and burst transfer, packet fragmentation, and the pigeon hole problem 
(please see the sidebar "How We Tested").  We ran the tests on 
implementations of TCP and IPDAC under WindowsNT 4.0, MacOS X, SCO UNIX 
4.6, and Trusted Solaris 2.5.1.

The results of the tests were mixed.  It takes about twice as long for 
IPDAC to deliver packets as TCP, however, IPDAC can handle packets up to 
50 times larger.  Avian Carrier protocol has similar fault tolerance 
capabilities as TCP, with the added ability to spawn additional carriers 
at the data ponds.  However, it does require additional time for the 
remote computer to bind the response packet to the carrier, thus reducing 
performance.  We found that TCP is much faster at small transfers.  For 
files over 200 kilobytes, AC begins to take over in speed.  It should be 
noted however, that most web and email traffic is under 70k.  We also 
found that AC was equally vulnerable to denial of service attacks through 
a special hunter packet that tracks the carrier signal and intercepts it. 
This causes the packet to drop immediately.  There was no significant 
difference between the operating systems used and TCP vs IPDAC 
performance. Results of our testing is available on page 102, chart 4-2 
and 4-3.
  
In conclusion, we found no appreciable reason to switch over to IP 
Datagrams on Avian Carriers at this time.  If the size of html, email, and 
graphics online increase dramatically, then the IPDAC protocol might be a 
good solution. Improvements to the fault tolerance and delivery speed 
would drastically enhance the viability of this protocol.  Work is already 
in progress for IP Datagrams on Avian Carrier version 2.0, which is 
supposed to tout an enhanced flight module and increased spawning speeds.  
We will continue to watch this protocol mature over time and report 
significant speed changes in future issues.