Fun and Games with TCP/IP

Phil R. Karn (
Mon, 18 Jan 88 16:49:06 EST

I posted this note on the USENET amateur packet radio group last weekend,
and a few people suggested that this group might appreciate it also.


From: (Phil R. Karn)
Newsgroups: rec.ham-radio.packet
Subject: Amateur TCP/IP path contest
Message-ID: <>
Date: 15 Jan 88 22:29:27 GMT
Organization: Bell Communications Research

Now that TCP/IP is really starting to take off in the amateur world, I think
it would be fun to start a running contest. The goal is to see who can come
up with the most complex, ad-hoc Internet path involving one or more amateur
packet radio links. This is inspired by Mike O'Dell's famous "worst wire"
contest. The only requirement is that the path must actually work! At a
minimum, you must successfully complete a three-way TCP handshake and then
successfully close the connection.

To start things off, I'd like to describe an experiment we did last weekend.
As many of you know, Telenet has this nifty service called PC Pursuit. From
any Telenet access number, you may connect to a remote dialout modem in in
something like 6 metropolitan areas. As long as you use it only during
evenings and weekends, it costs $25/month -- flat rate! Several amateur
TCP/IP groups have begun using PC Pursuit to link their otherwise isolated
"islands", with excellent results.

Last weekend Al, WB0MPQ (another resident of Warren, NJ) dialed up a PC
Pursuit link to Brian, WB6RQN, in the Maryland suburbs of DC. While the link
was up, I had Bob, WA3PXX, telnet briefly to a Bellcore machine named
"sabre" in Navesink, NJ. The path was as follows:

Node, location Link/Subnetwork
---- ---- ----------
wa3pxx.ampr (PC/XT)
                                222.06 Mhz AX.25 link
duplex RF repeater
Gaithersburg, MD(?)
                                223.66 Mhz AX.25 link
wb6rqn.ampr (PC/AT)
Germantown, MD
                                SLIP on 1200 baud dialup phone line (C&P Tel)
Telenet dialer port
Washington, DC
                                GTE Telenet X.25 network
Telenet TIP port
Rahway, NJ
                                SLIP on 1200 baud dialup phone line (NJ Bell)
wb0mpq.ampr (PC/XT)
Warren, NJ
                                147.525/430.05 Mhz full duplex AX.25 link
switch.ka9q.ampr (PX/XT)
Warren, NJ
                                KA9Q shack Ethernet
sun.ka9q.ampr (Sun 3/75)
                                SLIP on 9600 bps dialup phone line (NJ Bell)
Micom terminal switch
Piscataway, NJ
                                T-1 leased line (portion) (NJ Bell)
Micom terminal switch
Morristown, NJ
                                hardwired RS-232 line (Sun 2/170)
                                Lab Ethernet
Ethernet repeater
                                Machine room central Ethernet
DEC Lan Bridge
                                Building backbone Ethernet
Ethernet repeater
                                Building "core" Ethernet
Vitalink Translan
                                T-1 leased line (portion) (NJ Bell)
Vitalink Translan
Piscataway, NJ
                                T-1 leased line (portion) (NJ Bell)
Vitalink Translan
Navesink, NJ
                                building backbone Ethernet
DEC Lan Bridge
                                Building wing Ethernet
DEC Lan Bridge
                                Lab Ethernet (Vax 11/750?)

...and back.

This was a direct end-to-end connection; the TCPs on wa3pxx.ampr and spoke directly to each other. Excluding the endpoints
themselves, the path their IP datagrams took included:

8 Ethernets
5 IP gateways (2 Suns, 3 PC's running KA9Q net.exe)
4 radio frequencies on 3 amateur bands
3 dialup phone links (2 @ 1200 baud, 1 @ 9600 baud)
3 T-1 digital leased lines with multiplexors
3 Vitalink Translan IIIs
3 DEC Translan 100s
2 Micom terminal switches
2 Ethernet repeaters
1 full duplex RF repeater
1 public X.25 network (Telenet)
1 partridge in a pear tree :-)

So...can anybody top this? Who will be the first to include an amateur
satellite link in a TCP/IP path once AMSAT Phase 3-C is launched later this

73, Phil

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