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Can't run TCP/IP through AX.25 using Linux
Hi all,
I'm trying to setup a wireless link between two Linux using ConnexLink 900 MHz serial modems (http://www.aerocomm.com/Devices/link.htm). One side (ali) is a regular PC running Debian Linux testing and the other side (SLUG) is a NSLU2 running N7IPB's OpenSlug mod (http://wetnet.net/). The AX.25 link seem to work fine, I'm able to communicate between the two sides with "call", but I can't figure out how to pass TCP/IP through the link. Anyone idea about what's going on? Here's the relevant (I think) data from both hosts: ======================================== root@SLUG:~# cat /etc/ax25/axports #Name Callsign baudrate paclen window Description connex VA2JF-0 115200 1500 1 ConnexLink 900 MHz root@SLUG:/etc/ax25# /usr/sbin/kissattach -l /dev/ttyUSB0 connex 172.25.25.2 AX.25 port connex bound to device ax0 root@SLUG:~# ifconfig ax0 ax0 Link encap:UNSPEC HWaddr AC-82-64-94-8C-40-00-FF-00-00-00-00-00-00-00-00 inet addr:172.25.25.2 Bcast:172.25.255.255 Mask:255.255.0.0 UP BROADCAST RUNNING MTU:1500 Metric:1 RX packets:301 errors:0 dropped:0 overruns:0 frame:0 TX packets:61 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:10 RX bytes:17345 (16.9 KiB) TX bytes:2788 (2.7 KiB) root@SLUG:~# /sbin/route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 172.25.25.0 0.0.0.0 255.255.255.0 U 0 0 0 ax0 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 172.25.0.0 0.0.0.0 255.255.0.0 U 0 0 0 ax0 0.0.0.0 192.168.0.3 0.0.0.0 UG 0 0 0 eth0 root@SLUG:~# mheard Callsign Port Packets Last Heard VA2JF-1 connex 463 Mon Dec 19 21:08:44 root@SLUG:~# axparms -route list callsign dev mode digipeaters root@SLUG:~# ping -c 10 172.25.25.1 PING 172.25.25.1 (172.25.25.1): 56 data bytes --- 172.25.25.1 ping statistics --- 10 packets transmitted, 0 packets received, 100% packet loss ======================================== root@ali:~# cat /etc/ax25/axports # name callsign speed paclen window description connex VA2JF-1 115200 1500 1 ConnexLink 900 MHz root@ali:# kissattach -l /dev/ttyS1 connex 172.25.25.1 AX.25 port connex bound to device ax0 gfk@ali:~$ /sbin/ifconfig ax0 ax0 Link encap:AMPR AX.25 HWaddr VA2JF-1 inet addr:172.25.25.1 Bcast:172.25.255.255 Mask:255.255.0.0 UP BROADCAST RUNNING MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:165 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:10 RX bytes:0 (0.0 b) TX bytes:8085 (7.8 KiB) gfk@ali:~$ /sbin/route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 172.25.25.0 0.0.0.0 255.255.255.0 U 0 0 0 ax0 10.10.16.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 172.25.0.0 0.0.0.0 255.255.0.0 U 0 0 0 ax0 0.0.0.0 192.168.0.3 0.0.0.0 UG 0 0 0 eth0 gfk@ali:~$ mheard Callsign Port Packets Last Heard VA2JF connex 118 Sat Jan 28 16:44:54 gfk@ali:~$ sudo axparms -route list callsign dev mode digipeaters gfk@ali:~$ ping -c 10 172.25.25.2 PING 172.25.25.2 (172.25.25.2) 56(84) bytes of data. From 172.25.25.1 icmp_seq=1 Destination Host Unreachable From 172.25.25.1 icmp_seq=2 Destination Host Unreachable From 172.25.25.1 icmp_seq=3 Destination Host Unreachable From 172.25.25.1 icmp_seq=4 Destination Host Unreachable From 172.25.25.1 icmp_seq=5 Destination Host Unreachable From 172.25.25.1 icmp_seq=6 Destination Host Unreachable From 172.25.25.1 icmp_seq=7 Destination Host Unreachable From 172.25.25.1 icmp_seq=8 Destination Host Unreachable From 172.25.25.1 icmp_seq=9 Destination Host Unreachable From 172.25.25.1 icmp_seq=10 Destination Host Unreachable --- 172.25.25.2 ping statistics --- 10 packets transmitted, 0 received, +10 errors, 100% packet loss, time 9020ms , pipe 4 ======================================== Thanks a lot and 73, GFK's PS: I was able to make the link work with PPP, but PPP requires a full-duplex link. So I had to enable the full-duplex simulation of the modem. This cut the available bandwidth in half. I'm trying to see if AX.25 would perform better since it doesn't require full duplex. -- Guillaume Filion, ing. jr Logidac Tech., Beaumont, Québec, Canada - http://logidac.com/ PGP Key and mo http://guillaume.filion.org/ |
Can't run TCP/IP through AX.25 using Linux
Oh and another thing
PPP may be much more desirable because you can get huge compression gains (ie using BSD or deflate compression) I use to use it over an old 28K8 modem connection and got data rates in the order of 20-30x when moving logfiles around. As its compressed before it gets to the modem you arent limited by the 115K2 DTE rate either.. Cheers Bob VK2YQA wrote: Hi all, I'm trying to setup a wireless link between two Linux using ConnexLink 900 MHz serial modems (http://www.aerocomm.com/Devices/link.htm). One side (ali) is a regular PC running Debian Linux testing and the other side (SLUG) is a NSLU2 running N7IPB's OpenSlug mod (http://wetnet.net/). |
Can't run TCP/IP through AX.25 using Linux
Bob, thanks a lot for your help.
Is a -0 SSID valid for a hardware address? That's what was given in an example I followed, but I changed VA2JF-0 to VA2JF-2 just to be sure. It's also easier to match each host to it's IP address: VA2JF-1 has 172.25.25.1 and VA2JF-2 has 172.25.25.2. Is gfk@ali a root user? I had lots of trouble running TCP/IP AX25 apps as a non priv user on my old SuSE system. Something about denying port access. Didn't actually try "call" in user mode though. gfk@ali is not a root user, but I'm using sudo, so it shouldn't be a problem. This is a good advice, however. I'll use root whenever I playing with this. There has to be an ARP system somewhere. Indeed I think that the problem might be related to ARP. I used to think that ARP was just used on Ethernet, but I learn something new every day. Here's what I got on ali: ali:~# arp -an [...] ? (172.25.25.2) at incomplete on eth0 ali:~# arp -H ax25 -i ax0 -s 172.25.25.2 VA2JF-2 ali:~# arp -an [...] ? (172.25.25.2) at VA2JF-2 [ax25] PERM on ax0 Unfortunately, the slug is running busybox which is a very slimed down Unix. It looks like busybox's ifconfig is not compatible with ax25, hence the "Link encap:UNSPEC". I would like to try to compile a "real" ifconfig but unfortunately the slug is running with 288KB of free disk space. I'll need to transfer the system to a bigger flash drive when I get some free time. Also busybox doesn't have /usr/sbin/arp on the system, and /proc/net/arp doesn't list any ax25 address... OBTW I remember too that tcpdump doesnt work on an ax25 interface. You might try that to see if you get any valid data. This will show the arp conversation as well as IP You're right: ali:~# tcpdump -eni ax0 tcpdump: unknown data link type 3 I found a patch for tcpdump to work with ax25, but didn't tried it yet. http://he.fi/archive/linux-hams/200509/0060.html PPP may be much more desirable because you can get huge compression gains (ie using BSD or deflate compression) I use to use it over an old 28K8 modem connection and got data rates in the order of 20-30x when moving logfiles around. As its compressed before it gets to the modem you aren't limited by the 115K2 DTE rate either.. PPP requires full duplex and any radio link is inherently half-duplex. I had to use "full duplex simulation" in the radio firmware which is documented like this in the manual: ===== Full Duplex: This mode restricts Client radios to transmitting on odd numbered frequency hop bins and the Server to even numbered frequency hop bins. Though the RF hardware is still technically half duplex, it makes the transceiver seem full duplex. This can cause overall throughputs to be cut in half. Note: All transceivers on the same network must have the same setting for Full Duplex. === Ref: http://www.aerocomm.com/Docs/User_Manual_CL4490.pdf (p.16) Also, the RF baud rate is fixed at 76.8 Kbps, so in "full duplex simulation" it is effectively 33.6 Kbps. Even with compression, I speculated that half duplex AX.25 would perform better for activities such as web browsing where most of the heavy content (jpg images) is already compressed. I'll keep playing with this, thanks a lot for your help, GFK's -- Guillaume Filion, ing. jr Logidac Tech., Beaumont, Québec, Canada - http://logidac.com/ PGP Key and mo http://guillaume.filion.org/ |
Can't run TCP/IP through AX.25 using Linux
I found a patch for tcpdump to work with ax25, but didn't tried it yet.
http://he.fi/archive/linux-hams/200509/0060.html I tried the patch, it works well. It's worth a try. The patch did not apply cleanly, however. I had to apply some parts of the patch manually. For those who don't want to do that, I've made a tarball of the patched sources: http://guillaume.filion.org/tcpdump-3.9.3-ax25-1.tar.gz Here's the short readme: Full infos about this patched tcpdump available at: http://he.fi/archive/linux-hams/200509/0060.html To build this version of tcpdump: cd libpcap-0.9.3 ../configure make cd ../tcpdump-3.9.3 ../configure make ../tcpdump -eni ax0 73, GFK's -- Guillaume Filion, ing. jr Logidac Tech., Beaumont, Québec, Canada - http://logidac.com/ PGP Key and mo http://guillaume.filion.org/ |
Can't run TCP/IP through AX.25 using Linux
Okay I see.. problems problems! grin
When I first started playing with TCP/IP over packet maybe 12 years ago we did all we could to stop ARP broadcasts in our local subnet. All of the users had static ARP tables for that reason. We also had static host lookups. More recently I was involved in an IP over satellite paging/short message system where our initial bandwidth allocation was very small (3kb/sec). I made a lot of noise over that setup and suggested that if the b/w was unchangable then we should use static ARP tables. They increased the b/w instead, as a manual maintenance of an IP networks ARP's is a huge task! If you arent intent on using busybox you may want to try the Knoppix run from CD version that has the amateur radio add-ons. re PPP and HDX/FDX. Well in a way you are simply shifting the HDX switching back to the computer instead of using the radio hardware. I'd suspect that in the end you wouldnt do any better. I am however prepared to be shot down over this! I wonder if SLIP is any better handling HDX? It has less protocol overhead as well.. (from memory) Not sure about compression though. I have an application of sorts for this same mind of thing. My mother in law lives about 500 yards away just over the brow of a hill. There are also lots of trees! I doubt 2.4GHz will work and was looking at something with at least 115K throughout to connect her PC to our network. What has been your experience with the 900MHz gear and how well does it do with path obstacles? Oh and what did the units cost? Tnxs for the info on tcpdump. One day when I get back to radio... Cheers Bob W5/VK2YQA East Texas wrote: Bob, thanks a lot for your help. |
Can't run TCP/IP through AX.25 using Linux
Hi Bob,
I compiled net-tools on the slug and I now get this, which looks much better: root@slug:~# ifconfig ax0 ax0 Link encap:AMPR AX.25 HWaddr VA2JF-2 inet addr:172.25.25.2 Bcast:172.25.255.255 Mask:255.255.0.0 UP BROADCAST RUNNING MTU:1500 Metric:1 RX packets:52 errors:0 dropped:0 overruns:0 frame:0 TX packets:22 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:10 RX bytes:4238 (4.1 Kb) TX bytes:898 (898.0 b) net-tools also provided a version of arp. When I use it, though, I get this strange behavior: ===== root@slug:~# arp -an ? (192.168.0.5) at 00:01:53:80:57:E6 [ether] on eth0 root@slug:~# arp -H ax25 -i ax0 -s 172.25.25.1 VA2JF-1 root@slug:~# arp -an ? (172.25.25.1) at * [ax25] PERM on - ? (192.168.0.5) at 00:01:53:80:57:E6 [ether] on eth0 root@slug:~# cat /proc/net/arp IP address HW type Flags HW address Mask Device 172.25.25.1 0x3 0x6 * ax0 192.168.0.5 0x1 0x2 00:01:53:80:57:E6 * eth0 ===== I'm not sure if this is related to my version of arp or the kernel but I have a feeling that this is at the heart of the problem... If you arent intent on using busybox you may want to try the Knoppix run from CD version that has the amateur radio add-ons. The slug is in fact a NSLU2 from Linksys, which is not much bigger than my hand. There's no CD player on this, so I'm stuck with busybox if I want to use the NSLU2. http://xrl.us/NSLU2 re PPP and HDX/FDX. Well in a way you are simply shifting the HDX switching back to the computer instead of using the radio hardware. I'd suspect that in the end you wouldnt do any better. I am however prepared to be shot down over this! When working in FDX simulation, the radio hardware does the HDX switching 50:50. This is fixed and cannot be changed. I hope that AX.25 will switch it dynamically, sometimes 90:10 sometimes 70:30, so that I can get better performance when I need it. I'm not sure if it's worth the trouble, however. I have an application of sorts for this same mind of thing. My mother in law lives about 500 yards away just over the brow of a hill. There are also lots of trees! I doubt 2.4GHz will work and was looking at something with at least 115K throughout to connect her PC to our network. What has been your experience with the 900MHz gear and how well does it do with path obstacles? Oh and what did the units cost? I bought the Connexlink radios a couple months ago from Mouser. I bought the starter pack (Includes 1 server and 1 client Unit, RS-232 cables, Antennas, Power Supplies and Software) for US$225 (Mouser Stock No. 814-CL4490-232-SP). About 1 week after ordering, I got a phone call from a ConnexLink technician asking for informations about my project and giving me his phone number if I needed any help. My link is similar to yours, it's to my mother's house and I'm afraid that 2.4 GHz is not going to cut it unless I install a 100' tower on each side. It's 2.9 Km long (1.8 miles). I have a hill and lots of trees doing obstruction. Take a look at my path profile, I'm about at F0.9. It's made with Radio Mobile: http://www.cplus.org/rmw/english1.html Path profile scaled 10:1: http://guillaume.filion.org/80211lin...l-900-10-1.gif Path profile not scaled (1:1): http://guillaume.filion.org/80211lin...el-900-1-1.gif I haven't tested the hardware outside yet -- it's winter time here and I don't feel like climbing on the roof top full of snow. The specs says it can do 32 Km LOS with the stock antennas. I'm not LOS, but with yagi antennas replacing the stock antennas, I'm pretty sure that I could have a decent link. Common wisdom says that 900 MHz is too crowded for any good use, but I live in the country and there is not a lot of 900 MHz activity around here. The ConnexLink uses Frequency Hopping Spread Spectrum so it's more resistant to QRM. Your mileage may vary... Some links: http://www.mouser.com/aerocomm/ http://www.aerocomm.com/Devices/link.htm 73 GFK's -- Guillaume Filion, ing. jr Logidac Tech., Beaumont, Québec, Canada - http://logidac.com/ PGP Key and mo http://guillaume.filion.org/ |
Can't run TCP/IP through AX.25 using Linux
Hi again,
I did some tcpdump and it definitly looks like an ARP problem. # ./tcpdump -envi ax0 tcpdump: listening on ax0, link-type AX25 (AX.25), capture size 96 bytes [... root@slug:~# ping 172.25.25.1 ...] 17:30:01.703620 VA2JF-2 -6: Res 3, C/R 0, UI, ?, pf 0, length 101: (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto: ICMP (1), length: 84) 172.25.25.2 172.25.25.1: ICMP echo request, id 1691, seq 0, length 64 [... Notice the "VA2JF-2 -6" instead of "VA2JF-2 VA2JF-1" ...] [... root@ali:~# ping 172.25.25.2 ...] 17:31:24.033354 VA2JF-1 VA2JF-2: Res 3, C/R 0, UI, ?, pf 0, length 101: (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto: ICMP (1), length: 84) 172.25.25.1 172.25.25.2: ICMP echo request, id 6003, seq 1, length 64 [... I never get an answer from slug, I guess it's because slug's arp table doesn't contain ali's address ...] I'll get in contact with the creator of this kernel. 73 GFK's -- Guillaume Filion, ing. jr Logidac Tech., Beaumont, Québec, Canada - http://logidac.com/ PGP Key and mo http://guillaume.filion.org/ |
Can't run TCP/IP through AX.25 using Linux
Dont know about you guys, but since I still use an old 8 bit
Commodore128 computer I do all my packeting with the software DIGICOM128 AND IT WAS WRITTEN BY THE GERMANS WAY BACK. I use only the VHF band for military packet relays from Ft Huachuca Az to Schofield Bks here in Honoululu. Joe ABM6JF ************************************************** ******** * Ham KH6JF AARS/MARS ABM6JF QCWA WW2 VET WD RADIO SYSTEM* * Army MARS PRECEDED by AARS (Army Amateur Radio System) * * Hi State ARMY MARS COORDINATOR * ************************************************** ******** On Sat, 4 Feb 2006 wrote: Hi again, I did some tcpdump and it definitly looks like an ARP problem. # ./tcpdump -envi ax0 tcpdump: listening on ax0, link-type AX25 (AX.25), capture size 96 bytes [... root@slug:~# ping 172.25.25.1 ...] 17:30:01.703620 VA2JF-2 -6: Res 3, C/R 0, UI, ?, pf 0, length 101: (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto: ICMP (1), length: 84) 172.25.25.2 172.25.25.1: ICMP echo request, id 1691, seq 0, length 64 [... Notice the "VA2JF-2 -6" instead of "VA2JF-2 VA2JF-1" ...] [... root@ali:~# ping 172.25.25.2 ...] 17:31:24.033354 VA2JF-1 VA2JF-2: Res 3, C/R 0, UI, ?, pf 0, length 101: (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto: ICMP (1), length: 84) 172.25.25.1 172.25.25.2: ICMP echo request, id 6003, seq 1, length 64 [... I never get an answer from slug, I guess it's because slug's arp table doesn't contain ali's address ...] I'll get in contact with the creator of this kernel. 73 GFK's -- Guillaume Filion, ing. jr Logidac Tech., Beaumont, Québec, Canada - http://logidac.com/ PGP Key and mo http://guillaume.filion.org/ |
Can't run TCP/IP through AX.25 using Linux
I wonder if slug has an issue with dashes in the hardware address?
Either that or it is smart enough to notice the first 5 chars of the hardware address are the same source dest. As you say though it isnt working! Looks like you are getting closer! Okay on the 50:50 half duplex timing of the boxes. That seems kind of a strange way to do it. Would have expected the manufacturer to use dynamic b/w allocation. I had a quick look at SLIP/CSLIP but didnt really establish how effective it was on HDX. I assume that ppp is unusable because of the backgound handshaking that goes on (ipcp etc)? Is it that or timeouts and retries at the IP layer? Tnxs for the info on your purchase. I dont want to spend lots of dollars on my attempt. Would rather invest in 2nd hand than new equipment. The MIL is using dial-up at the moment so it isnt exactly urgent. I have a mind to use one of the scrap microwave radios from work but they start at 2.4GHz. (We manufacture data equip up to 12GHz and DS1 through E3) My path actually looks a lot better than yours though! Cheers Bob wrote: Hi again, I did some tcpdump and it definitly looks like an ARP problem. |
Can't run TCP/IP through AX.25 using Linux
I've been running the ConnexLink 900 Mhz serial modems for over a year
now to connect my house network to my business network in a rural area. The networks are Windows based and the link runs PPP using the radio's full duplex setting. The link is clean for ping, telnet, ftp, and email. Unfortunately, I never was able to get any browser to work without it coming to a screeching halt with lots of TCP/IP retransmissions. I contacted Aerocomm tech support (Sean) about this several times, but it appears that no one else really uses the ConnexLinks on TCP/IP (they have a newer product ConnexNet that does). I really don't have a clue why the link fails with a browser, except that some piece of the hardware/software path must be failing with the heavy full duplex traffic created by browser and then snowballs with the TCP/IP retransmissions. I am curious if you are able to get PPP to work reliably with a browser to web sites with a lot of graphics that result in multiple simultaneous connections. If you are (and I would not be surprised if your link would work, given the different hardware/software pieces), then it gives me hope that one day I might be able to get my link to work properly when I have the time to fix it. And if you get the radios to run faster on AX.25, then that is even a greater achievement. By the way, my radio link is solid (no problem there). There are two yagi antennas pointing at each other and the signal is great even through the trees. wrote: Hi all, I'm trying to setup a wireless link between two Linux using ConnexLink 900 MHz serial modems (http://www.aerocomm.com/Devices/link.htm). One side (ali) is a regular PC running Debian Linux testing and the other side (SLUG) is a NSLU2 running N7IPB's OpenSlug mod (http://wetnet.net/). The AX.25 link seem to work fine, I'm able to communicate between the two sides with "call", but I can't figure out how to pass TCP/IP through the link. Anyone idea about what's going on? Here's the relevant (I think) data from both hosts: ======================================== root@SLUG:~# cat /etc/ax25/axports #Name Callsign baudrate paclen window Description connex VA2JF-0 115200 1500 1 ConnexLink 900 MHz root@SLUG:/etc/ax25# /usr/sbin/kissattach -l /dev/ttyUSB0 connex 172.25.25.2 AX.25 port connex bound to device ax0 root@SLUG:~# ifconfig ax0 ax0 Link encap:UNSPEC HWaddr AC-82-64-94-8C-40-00-FF-00-00-00-00-00-00-00-00 inet addr:172.25.25.2 Bcast:172.25.255.255 Mask:255.255.0.0 UP BROADCAST RUNNING MTU:1500 Metric:1 RX packets:301 errors:0 dropped:0 overruns:0 frame:0 TX packets:61 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:10 RX bytes:17345 (16.9 KiB) TX bytes:2788 (2.7 KiB) root@SLUG:~# /sbin/route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 172.25.25.0 0.0.0.0 255.255.255.0 U 0 0 0 ax0 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 172.25.0.0 0.0.0.0 255.255.0.0 U 0 0 0 ax0 0.0.0.0 192.168.0.3 0.0.0.0 UG 0 0 0 eth0 root@SLUG:~# mheard Callsign Port Packets Last Heard VA2JF-1 connex 463 Mon Dec 19 21:08:44 root@SLUG:~# axparms -route list callsign dev mode digipeaters root@SLUG:~# ping -c 10 172.25.25.1 PING 172.25.25.1 (172.25.25.1): 56 data bytes --- 172.25.25.1 ping statistics --- 10 packets transmitted, 0 packets received, 100% packet loss ======================================== root@ali:~# cat /etc/ax25/axports # name callsign speed paclen window description connex VA2JF-1 115200 1500 1 ConnexLink 900 MHz root@ali:# kissattach -l /dev/ttyS1 connex 172.25.25.1 AX.25 port connex bound to device ax0 gfk@ali:~$ /sbin/ifconfig ax0 ax0 Link encap:AMPR AX.25 HWaddr VA2JF-1 inet addr:172.25.25.1 Bcast:172.25.255.255 Mask:255.255.0.0 UP BROADCAST RUNNING MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:165 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:10 RX bytes:0 (0.0 b) TX bytes:8085 (7.8 KiB) gfk@ali:~$ /sbin/route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 172.25.25.0 0.0.0.0 255.255.255.0 U 0 0 0 ax0 10.10.16.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0 172.25.0.0 0.0.0.0 255.255.0.0 U 0 0 0 ax0 0.0.0.0 192.168.0.3 0.0.0.0 UG 0 0 0 eth0 gfk@ali:~$ mheard Callsign Port Packets Last Heard VA2JF connex 118 Sat Jan 28 16:44:54 gfk@ali:~$ sudo axparms -route list callsign dev mode digipeaters gfk@ali:~$ ping -c 10 172.25.25.2 PING 172.25.25.2 (172.25.25.2) 56(84) bytes of data. From 172.25.25.1 icmp_seq=1 Destination Host Unreachable From 172.25.25.1 icmp_seq=2 Destination Host Unreachable From 172.25.25.1 icmp_seq=3 Destination Host Unreachable From 172.25.25.1 icmp_seq=4 Destination Host Unreachable From 172.25.25.1 icmp_seq=5 Destination Host Unreachable From 172.25.25.1 icmp_seq=6 Destination Host Unreachable From 172.25.25.1 icmp_seq=7 Destination Host Unreachable From 172.25.25.1 icmp_seq=8 Destination Host Unreachable From 172.25.25.1 icmp_seq=9 Destination Host Unreachable From 172.25.25.1 icmp_seq=10 Destination Host Unreachable --- 172.25.25.2 ping statistics --- 10 packets transmitted, 0 received, +10 errors, 100% packet loss, time 9020ms , pipe 4 ======================================== Thanks a lot and 73, GFK's PS: I was able to make the link work with PPP, but PPP requires a full-duplex link. So I had to enable the full-duplex simulation of the modem. This cut the available bandwidth in half. I'm trying to see if AX.25 would perform better since it doesn't require full duplex. -- Guillaume Filion, ing. jr Logidac Tech., Beaumont, Québec, Canada - http://logidac.com/ PGP Key and mo http://guillaume.filion.org/ |
Can't run TCP/IP through AX.25 using Linux
If I may answer first...
TCP/IP is suppose to self calculate retry etc periods based on the first few packet failures. I am surprised you are having problems with the link at all. Perhaps some massaging of the TCP retry parameters might be in order. I'll admit I dont know where to do that in Windows without looking it up. It will be as registry setting. I wonder if you are also using plain serial ports at each end or some kind of ethernet converter. That can mess things up as TCP/IP thinks it has a faster throughput speed than it really doesnt. The other possibility is that serial hardware handshaking is broken although FTP would be affected by that. (Depends on the direction and which end has failed though) Lowering your DTE speed may also help. As a simple workaround you can limit the number of concurrent http requests your browser will allow. Once again I dont know how this is done in IE but Firefox has a about:config parameter network.http.maximum.connections or similar. The end effect will be that web pages with lots of internal lnks (eg pictures) will tend to load more one after the other than bits at the same time. Email, FTP and telnet use a port for each direction whereas web browsers can use 100+ source ports to get a web page. If you wish to try this and dont have Firefox, download it and gimee a shout and I'll walk you through the config changes. I have also heard the SLIP might be a better way to go over these links because of the half duplex factor. I'll admit I havent tried this but it wont hurt to try. W2K and above have SLIP available if you want to play with it. Strangely I am thinking of using a 900MHz serial link to my mother in laws house. The reason I am not using 802.11 Ethernet is path obstructions. One option by the way, if you want to throw lots of money at it, is to setup a second link such that the whole things runs a "real" fullduplex. Lastly I havent checked around on the web on this topic. Perhaps others have had this issue and found a solution. Cheers Bob Braath Waate wrote: I've been running the ConnexLink 900 Mhz serial modems for over a year now to connect my house network to my business network in a rural area. The networks are Windows based and the link runs PPP using the radio's full duplex setting. |
Can't run TCP/IP through AX.25 using Linux
Thanks Bob for all of your good suggestions.
I've tried playing around with some of the TCP/IP tuning. I also played around with the max-connections in Explorer and Firefox. Not much difference in performance. I did swap a unshielded serial cable (the radios are directly connected to the computers' serial ports) with a shielded cable, and that seemed to improve the performance. The serial lines are fairly long (60') to get to the antennas which are colocated with the radios. I would say the system is usable (slow) with a browser, but not good with heavy traffic, which results in significantly more retransmissions and reset connections. The reason why the link is disappointingly slow is that it only runs at 19 kbps. According to the Aerocomm AC4490 manual, the maximum throughput of the radio in stream mode is 57.6 kbps, acknowledge mode is 38k and acknowledge with full/duplex is 19k (full/duplex is only supported in acknowledge mode). Running PPP or SLIP requires the full/duplex hardware, so 19k is all I can get. I'm in the market for better but inexpensive 900 Mhz radios to replace the Aerocomms, if anyone has any suggestions. |
Can't run TCP/IP through AX.25 using Linux
That RS232/serial run is in my view way too long if you are running at
115K2, even when shielded. I would suspect that noise is being introduced into the circuit. RS232 isnt a balanced system like RS485 or XBaseT ethernet so you dont gain the benefits of common mode rejection. You may even have earth loops occurring in your computer/mains/ground setup that puts main noise onto the cable shield. The simple test is to reduce the DTE rate from the computer to the radio to the next step down to see if that helps. If the modems offer hardware compression you might lose your peak speed but gain a higher reliability. Generally speaking the slower the bit rate the longer the cable can be. The data rate problem is the same thing that gfilion was fighting on. I understand the Aerocomm fixes the TX/RX ratio at 50% to make PPP work and thus you get the low data rate. You may of course also be suffering from radio interference. I remember the Cisco Aironet boxes use to keep stats as to their performance. If the Aerocomm boxes do that may be a place to check. One simple thing you can do if you think it is another transmitter is to change to horizontal polarisation in the hope that most other users will be on vertical. I have had a look around for Ethernet radios on 900MHz and they arent real cheap (like USD700/pair etc). The serial offerrings all seem to have the same rate limitations you have encountered and as yet I havent seen a USB connected one (to gain a higher rate than 115K2). They seem to be more for telemetry/SCADA use rather than a FDX internet link. My flippant suggestion to get another Aerocomm pair and connected them for full duplex operation might be cost viable for you. You'll need to play with the hardware a bit but I dont see any problems if you can tell the modems to stay in the right mode. I get the impression that this will then get you 57K6. I am seriously thinking of taking some of my works 2.4GHz RF modules for TX and RX and supplying my own QAM modulation scheme to them. The idea being to run maybe 1MB/sec via the USB port. I can do that as a radio amateur but will need to check whether I can use the ISM band in that manner. I can certainly tune it to the FCC spec but dont know if I have to go through a type approval process. A very long term project I am afraid. In that vein I am also looking for AX25/packet QAM I/Q modems that would do that part for me. Good luck! Cheers Bob Braath Waate wrote: Thanks Bob for all of your good suggestions. |
Can't run TCP/IP through AX.25 using Linux
Yes, good suggestion. I am running the serial lines at 115K, I will try
to run at 57 or 38 or even 19 and see if that improves the link. Connexlink does have a signal strength register (report last RSSI) and has some DOS software to manage it, but I have been reluctant to spend the time on the radio section because the 19K limit is disappointing enough for web access, even if it were reliable. I'm sorry I don't understand the radio pair suggestion; wouldn't the pair of radios just interfere with each other? Is the idea to hook the tx lead of the serial port to one radio and the rx lead to the other? How would they hook to the antenna? -- Braath |
Can't run TCP/IP through AX.25 using Linux
Hi Braath
The kind of stats I am talking about is more the bit error rate one. ie what percentage of the radio packects are mangled or not getting through. It is common in a radio system to have some percentage of failure. I use to administer two non licensed links, one on 2.4Ghz and the other on 5.7. Towards the end of its useful life the 2.4GHz link had about 90% retries mainly from interferring sources. In that case we got much better reliability limiting it to the 1MB speed (as against 11). The newer less populated 5.7GHz link ran about 20% retries. The fullduplex radio pair configuration I suggested would use separate frequencies and maybe even antenna polarisation/space separation to reduce interference. ie two antennas at each end. Using a diplexor to allow two boxes on the one antenna is probably a bit cost wasteful. The idea is that at one end you force one box into transmit mode and the other to receive. You also have to specify a fixed channel instead of allowing automatic operation. The node names would also have to be paired. Connection to the computer is as you stated but some configuration of the handshaking lines (RTS, CTS, DTR etc) would also be needed. I expect that Connexlink would have already done this with their equipment so there may even be an application note on it available. It would of course be smart to run all lines back to the PC and do the patching there, in case you want to send commands to the unit itself and need both TX/RX lines available. Cheers Bob Braath Waate wrote: -- I'm sorry I don't understand the radio pair suggestion; wouldn't the pair of radios just interfere with each other? Is the idea to hook the tx lead of the serial port to one radio and the rx lead to the other? How would they hook to the antenna? |
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