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PA2AGA > HDDIG 20.09.00 23:28l 186 Lines 6897 Bytes #999 (0) @ EU
BID : HD_2000_254B
Read: DC1TMA GUEST
Subj: HamDigitalDigest 2000/254B
Path: DB0AAB<DB0SL<DB0RGB<DB0MRW<DB0ERF<DB0BRI<DB0HAG<DB0ACH<PI8JOP<PI8ZAA<
PI8HGL
Sent: 000920/1905Z @:PI8HGL.#ZH1.NLD.EU #:16273 [Den Haag] FBB $:HD_2000_254B
From: PA2AGA@PI8HGL.#ZH1.NLD.EU
To : HDDIG@EU
Date: Sun, 17 Sep 00 16:39:00 MET
Message-Id: <hd_2000_254B>
From: pa2aga@pe1mvx.ampr.org
To: hd_broadcast@pa2aga.ampr.org
X-BBS-Msg-Type: B
UDP is a connectionless oriented protocol for things like audio and video.
It doesn't do much more than provide ports and checksum to the IP protocol.
TFTP (Trivial File Transfer Protocol) and NFS (Network File System) were two
early protocols that rode on UDP. Not because the were unreliable, but
because
they were used on an Ethernet LAN where data loss was statistically low.
Have you ever done NFS across the Internet? Bad, I know. Recent
implementations (Ver 3) allow you to specify TCP for NFS.
------------------------------
Date: Sun, 17 Sep 2000 04:11:19 GMT
From: "Cathryn Mataga" <cathryn@junglevision.com>
Subject: APRS-TCP/IP help
> On Wed, 13 Sep 2000, Ed_Woodrick wrote:
> > While TCP/IP supports broadcasts, the Internet does not. There is a
> > permutation called multi-cast that is close, but it also isn't widely
> > supported. So, to do what you want, you will have to use transmissions to
> > all systems that you want to send or receive data from . UDP would
probably
> > be the protocol that you would use.
>
I did look into multi-cast a bit. And, the funny thing is I think it would
be very well suited to transmitting APRS data across the country. The
issues seem to be...
1. Most of the new multi-cast work seems to be with IPV6, and not old
IPV4 multicast. So, I'm not sure how well all the code is maintained.
(This is just a perception of mine, so maybe I'm wrong here.)
2. Windows and Linux both support multicast. However, you need
a Unix machine of some kind to run 'mrouted' which allows you to tunnel
between parts of the net which don't support multicast.
3. But, yes you can run multicast routers on your local LAN, and
then link to other people also running multicast routers. And somehow,
when you send broadcast packets, the routers are supposed to figure
out somehow how to get the bytes from here to there.
4. The application programming API for multicast is super simple
and easy to understand. Writing code is no big deal.
5. Multicast doesn't guarantee delivery. It's more like UDP than TCP/IP.
6. I believe mrouted is supposed to be smart enough only to route the
packets to those who want to hear them. So, if say, you wanted to hear
all the APRS packets in New York City, but you were in Las Vegas,
somehow, mrouted would get that data to you. I have no idea how
well this works. Supossedly there was a network one time running
ip multicast called the mbone -- but I can't find many references to it
lately.
7. Obviously there is zero code for any of this right now. Somebody
would have to do some programming to put all this together.
------------------------------
Date: Sun, 17 Sep 2000 08:27:53 GMT
From: nomail@rob.knoware.nl (Rob Janssen)
Subject: APRS-TCP/IP help
D. Stussy <kd6lvw@bde-arc.ampr.org> wrote:
>OK - but all the applications that I have seen which use UDP are either of
the
>query/response type (such as DNS) or of the unsolicited information type
(such
>as for dynamic routing). I've never seen nor heard of an application which
>takes multiple packets.
You cannot know everything. But NFS is such an application. It uses UDP
to send data between two systems that have a session in the sense that one
knows about a filesystem on the other, and opens and closes files on it.
But there is no real session as in TCP, and the server system can be
rebooted between client requests without losing anything.
Rob
--
+----------------------------------+--------------------------------------+
| Rob Janssen pe1chl@amsat.org | WWW: http://www.knoware.nl/users/rob |
| AMPRnet: rob@pe1chl.ampr.org | AX.25 BBS: PE1CHL@PI8WNO.#UTR.NLD.EU |
+----------------------------------+--------------------------------------+
------------------------------
Date: Sun, 17 Sep 2000 08:30:27 GMT
From: nomail@rob.knoware.nl (Rob Janssen)
Subject: APRS-TCP/IP help
Cathryn Mataga <cathryn@junglevision.com> wrote:
>5. Multicast doesn't guarantee delivery. It's more like UDP than TCP/IP.
Multicast is on the IP level. UDP can be used with multicast, TCP cannot.
Because TCP assumes it is talking to a peer that will send it
acknowledgments, that confirm the reception of sent data (which can then
be deleted from a queue). This isn't the case with multicast because one
receiver may miss data that another one got.
Rob
--
+----------------------------------+--------------------------------------+
| Rob Janssen pe1chl@amsat.org | WWW: http://www.knoware.nl/users/rob |
| AMPRnet: rob@pe1chl.ampr.org | AX.25 BBS: PE1CHL@PI8WNO.#UTR.NLD.EU |
+----------------------------------+--------------------------------------+
------------------------------
Date: Sat, 16 Sep 2000 20:22:29 -0500
From: "Steve Sampson \(K5OKC\)" <ssampson@nospam.radio-link.net>
Subject: Auctions are like Pawn Shops, was: Beware of W4WWB
This is a multi-part message in MIME format.
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charset="iso-8859-1"
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> I am deeply disappointed to warn you not to deal with _____________.
> He advertised a radio on ebay that was complete, but needed some work. =
What
> arrived was a parts radio - Pieces were missing and it will not power =
up.
> After he ignored my emails I contacted him by phone and in his best =
good ole
> boy drawl he told me " you bought it, you own it". He would not allow =
me to
> return it for a refund. I know that ebay is a take your own risk =
venture -
> but deliberately lying about the condition of the radio to sell it is
> dishonest. What a disgrace to the ham community. Don't be suckered by =
this
> man like I was.
There is a procedure to follow on eBay, and I suggest you follow it,
go read the docs.
------=_NextPart_000_0033_01C0201B.D5F23500
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charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META http-equiv=3DContent-Type content=3D"text/html; =
charset=3Diso-8859-1">
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<STYLE></STYLE>
</HEAD>
<BODY>
<DIV><FONT face=3DArial size=3D2></FONT>
<DIV><FONT face=3DArial size=3D1>> I am deeply disappointed to warn =
you not to=20
deal with _____________.<BR>> He advertised a radio on ebay that was=20
complete, but needed some work. What<BR>> arrived was a parts radio - =
Pieces=20
were missing and it will not power up.<BR>> After he ignored my =
emails I=20
contacted him by phone and in his best good ole<BR>> boy drawl he =
told me "=20
you bought it, you own it". He would not allow me to<BR>> =
return it for=20
To be continued in digest: hd_2000_254C
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