Monday, November 26, 2007

Linux TCP Congestion Variants

High level overview of the TCP congestion control mechanisms

LINK

Saturday, November 17, 2007

ADI Pronghorn Info

ADI Link here

Thursday, November 15, 2007

EIA-561

Use this pinout with any ethernet cable for RS-232 on RJ45 connectors, courtesy of this blog

 pair     4-pair     RJ-45  color   DB9  DB25  signal  circuit  DTE  DCE
-----------------------------------------------------------------------
1 blue/white 4 red 5 7 SG AB - -
1 white/blue 5 green 2 3 RD BB in out
2 white/orange 3 black 4 20 DTR CD out in
2 orange/white 6 yellow 3 2 TD BA out in
3 white/green 1 blue 9 22 RI CE in out
3 green/white 2 orange 1 8 DCD CF in out
4 white/brown 7 brown 8 5 CTS CB in out
4 brown/white 8 white 7 4 RTS CA out in
- - - - 6 6 DSR CC in out

column legend:
pair = twisted pair number in standard 4-pair cable
4-pair = base/stripe colors in standard 4-pair cable
RJ-45 = pin number
color = wire color on standard RJ-45 connector
DB9 = pin number
DB25 = pin number
signal = EIA signal name (abbreviated form)
circuit = EIA circuit designation
DTE = electrical input or output for Data Terminal Equipment (PC)
DCE = electrical input or output for Data Communications Equipment (modem)

Tuesday, November 13, 2007

PXEBoot from LiveCD

Here is a handy utility from the folks at metrix.net that will allow you to boot several different apps onto an embedded device such as Soekris boards...

PXEBootLiveCD

Calculate POE voltage loss

http://www.demarctech.com/techsupport/poecalculate.htm

Saturday, November 10, 2007

ADM 9F8 GR Pinout

ADM 9F8 GR - rj45 to db9 fem frys part number 2402340

1 - blu
2 - org
3 - blk
4 - red
5 - grn
6 - yel
7 - brn
8 - wht

Tuesday, November 6, 2007

Linux Filesystems

A decent article to get your appetite for linux filesystems

here

OpenBSD 4.2

Since I have done some porting for the wireless project this was of particular interest

"Enable interrupt holdoff on sis(4) chips that support it. Significant performance gain for slower CPU devices with sis(4), such as Soekris." Would you like to tell us more about this?

Chris Kuethe: Quite a number of network adapters have a configurable mechanism to prevent the machine from being run into the ground under network load. This is known as holdoff, mitigation or coalescing. The general idea is that the network adapter does not immediately raise an interrupt as soon as a frame is arrived; rather the interrupt is delayed a short time—usually one frame or a few hundred microseconds—in case another frame might arrive very soon thereafter.

Picking a good delay value, or set of conditions under which to signal the arrival of a frame is not easy. Too much holdoff and network performance is severely degraded, too little and no benefit will be noticed. When ping times go up and TCP stream speeds go down, you're delaying too much.

In the case of the Soekris (or anything else that uses sis(4)), interrupt holdoff was not enabled. By enabling holdoff, we allow the network controller to delay and buffer a few frames. This spreads cost of the interrupt across several packets.

full story

Amazon GPS

Mapping Africa

Monday, November 5, 2007

More mobile wireless adhoc

http://moment.cs.ucsb.edu/aodv-ietf/

Wireless Mobile Mesh

Software for creating adhoc mobile networks.

http://www.mitre.org/work/tech_transfer/mobilemesh/

SIP Proxy/Registrar

Siproxd is a proxy/masquerading daemon for the SIP protocol. It handles registrations of SIP clients on a private IP network and performs rewriting of the SIP message bodies to make SIP connections work via an masquerading firewall (NAT).

It allows SIP software clients (like kphone, linphone) or SIP hardware clients (Voice over IP phones which are SIP-compatible, such as those from Cisco, Grandstream or Snom) to work behind an IP masquerading firewall or NAT router.

SIP (Session Initiation Protocol, RFC3261) is the protocol of choice for most VoIP (Voice over IP) phones to initiate communication. By itself, SIP does not work via masquerading firewalls as the transfered data contains IP addresses and port numbers. There do exist other solutions to traverse NAT existing (like STUN, or SIP aware NAT routers), but such a solutions has its disadvantages or may not be applied to a given situation. Siproxd does not aim to be a replacement for these solutions, however in some situations siproxd may bring advantages.


http://siproxd.sourceforge.net/