[ax25-layer2] AX.25 over raw serial interface

[John Wiseman]

The modem might, but you won't know the length when it arrives. How do
you tell when the I frame ends and the next frame starts? 
 
Unless you aren't really using ax.25
 
 
John
 

-----Original Message-----
From: ax25-layer2-bounces at tapr.org [mailto:ax25-layer2-bounces at tapr.org]
On Behalf Of Can Yuce
Sent: 29 July 2009 21:08
To: Discussion of Link Layer use of AX.25
Subject: Re: [ax25-layer2] AX.25 over raw serial interface


Thanks John but in fact I don't need to tell the length of packets
anyway to the modem. 
This is transparent and the modem takes care of it.

--
Can Yuce 




On Wed, Jul 29, 2009 at 10:54 PM, John Wiseman
<john.wiseman at ntlworld.com> wrote:


Actually you do need some form of framing. Even if you don't care about
errors, you can't tell the length of an I Frame without it.
 
73,
John G8BPQ
 

-----Original Message-----
From: ax25-layer2-bounces at tapr.org [mailto:ax25-layer2-bounces at tapr.org]
On Behalf Of Can Yuce
Sent: 29 July 2009 20:45
To: Discussion of Link Layer use of AX.25
Subject: Re: [ax25-layer2] AX.25 over raw serial interface



Thanks Samuel, in fact I don't deal with any other protocols slip, ppp
etc. over
the line since the main purpose of  using the system is to experiment
AX.25
packet structures under laboratory conditions. As I've mentioned before,

our standalone modems need to be connected to the DTE equipment(PCs)
by RS-232 interface so, we don't need special caution for flow, error
control, sync etc.

 
--
Can Yuce



On Wed, Jul 29, 2009 at 10:26 PM, Samuel A. Falvo II
<sam.falvo at gmail.com> wrote:


On Wed, Jul 29, 2009 at 12:13 PM, Jay Nugent<jjn at nuge.com> wrote:
>   On a JNOS system, this would simple be known as a "slip' link.  But
I
> am presuming you are not running JNOS.


I'm not familiar with JNOS, but if JNOS' slip is what I think it is,
"slip" is a different protocol from AX.25.  The Serial Line IP
protocol is a raw frame-relay protocol that wraps packets in $C0
bytes.  No source/destination addresses, control, or type fields.  No
CRCs either.  If data gets corrupted on a serial link, you're screwed.
 But, that's OK, because it's operating under the assumption that TCP
will pick up the slack.

I interpreted Can's request as the ability to pass raw AX.25 frames
between two machines.  In this case, PPP is the closest available
relative (since both AX.25 and PPP are HDLC protocols), but as this is
the AX.25 SIG list... ;D

--
Samuel A. Falvo II


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