Firstly, what is SAM support? One end of an SS7 link initialises a new call by sending an Initial Address Message (IAM). All SS7 software stacks support this and usually it’s enough. One case where it’s not enough is when one wants to address a phone number with more than the E.164 standard max length of 16  (usually to pass additional information tacked on the start, end of or even replacing an A or B number). In this scenario, SS7 uses a Subsequent Address Message (SAM) to send the additional digits. Most / all mainstream Asterisk SS7 software stacks do not support this.

The platform and software used is as follows:

• Ubuntu 10.04 LTS standard CLI install;
• dahdi-linux-complete-2.4.0 from the archives (direct link);
• a patched version of libss7 supporting SAM via SVN (see below);
• a patched version of chan-dahdi via SVN (see below);
• Asterisk 1.6.0.28 from the archives (direct link);
• Asterisk Addons 1.6.0.6 from the archives (direct link);
• Sangoma Wanpipe 3.5.24 (direct link).

Yes, I know some of the above are obsolete. Unfortunately it’s what’s required for everything to play nicely together. And, guess what, it works!

Before You Start

Ensure you have all the necessary packages for building the packages:

apt-get install build-essential libnewt-dev subversion    \
   libsqlite3-dev libsnmp-dev bison libtool flex          \
   autoconf2.13 libmysqlclient-dev

You can assume the working directory is /usr/local/src in the following.

Installing dahdi-linux-complete

Download and extract dahdi-linux-complete into /usr/local/src. Then, in the same directory, create some symbolic links:

ln -s dahdi-linux-complete-2.4.0+2.4.0/linux dahdi-linux
ln -s dahdi-linux-complete-2.4.0+2.4.0/tools dahdi-tools

Now build dahdi-linux:

cd dahdi-linux
make
make install

Now move onto dahdi-tools:

cd dahdi-tools
./configure
make menuconfig # (and select tools or accept defaults)
make
make install
make config

Installing libss7

There is a patched version of Digium’s libss7 referred to as Attila’s libss7 available via SVN. Download and install it:

svn co https://observer.router.hu/repos_pub/libss7/trunk alibss7
cd alibss7
make
make install

Installing Asterisk

Download and extract the Asterisk 1.6.0.28 package reference above.

cd asterisk-1.6.0.28

Now this next bit is very important and easy to miss - you also need a patched version of chan_dahdi.c that is compatible with the patched version of libss7. This is also available from SVN:

svn co https://observer.router.hu/repos_pub/chan_dahdi/trunk achan_dahdi

Then copy it to your Asterisk source:

cp achan_dahdi/chan_dahdi.c asterisk-1.6.0.28/channels/chan_dahdi.c

Now continue with the Asterisk installation:

./configure
make menuconfig
make
make install
make samples
make config

Install Asterisk Addons (optional)

Download and unpack the above referenced add ons package and build and install:

cd asterisk-addons-1.6.0.6
./configure
make menuconfig
make
make install
make samples

Sangoma Wanpipe

I’m using one of Sangoma’s E1 / T1 interface cards and so I need Wanpipe also. I’m using version 3.5.24 and preceed as follows after unpacking:

cd wanpipe-3.5.24./Setup install

During the install, follow these prompts:

• select option 2 => Asterisk/Dahdi Support;
• enter path /usr/local/src/dahdi-linux (for Zaptel path prompt);
• select defaults for everything else;
• you DO want to install start-up scripts;
• you DO to configure wanpipe devices for DAHDI;
• you DO want to generate /etc/asterisk/chan_dahdi.conf and:
  • select E1 / T1 as appropriate;
  • select line framing and encoding;
  • choose clock source;
  • select Zaptel/Dahdi – PRI CPE as signalling;
  • select National ISDN 2 as switch type;
  • do not enable hardware DTMF detection;
  • use all channels;
  • select dial plan context as appropriate;
• and continue for other ports as necessary;
• finally, choose Save cfg: Stop Asterisk & Wanpipe now
• you would like wanrouter to start on system boot;
• and you would like to execute ‘dahdi_cfg’ each time wanrouter starts.

Configuration Steps

We now need to set various options in Wanpipe, Dahdi and Asterisk for SS7 as it’s PRI/ISDN by default.

Edit all /etc/wanpipe/wanpipeX.conf files as necessary and change:

 TDMV_DCHAN              = 16

to

TDMV_DCHAN              = 0

Now edit /etc/dahdi/system.conf and change (for example):

span=1,1,0,ccs,hdb3,crc4
bchan=1-15,17-31
echocanceller=mg2,1-15,17-31
hardhdlc=16

to

span=1,1,0,ccs,hdb3,crc4
bchan=2-31
echocanceller=mg2,2-31
mtp2=1

which of course assumes signalling is on channel 1. If you have voice only links, you might need something like:

span=1,0,0,ccs,hdb3,crc4bchan=1-31
echocanceller=mg2,2-31

Lastly, we need to configure Asterisk. Replace lines such as:

;Sangoma A102 port 1 [slot:4 bus:5 span:1]
switchtype=national
context=from-pstn
group=0
echocancel=yes
signalling=pri_cpe
channel =>1-15,17-31

with an appropriate configuration. Mine follows below with some edits and some important notes at the end:

;Sangoma A102 port 1 [slot:4 bus:5 span:1]
switchtype=national
context=from-pstn
group=0
echocancel=yes

signaling=ss7
ss7type=itu
ss7_called_nai=dynamic
ss7_calling_nai=dynamic
ss7_internationalprefix=00
ss7_nationalprefix=0
ss7_subscriberprefix=
ss7_unknownprefix=
linkset=1
pointcode=1
adjpointcode=2
defaultdpc=3
networkindicator=national_spare
cicbeginswith=2
channel=2-31
sigchan=1

• Set pointcode, adjpointcode and defaultdpc as appropriate;
• set networkindicator as appropriate and ensure it matches the other end (you can see what you’re being sent and what you’re sending via ss7 debug;
• cicsbeginwith is normally 1 but the telco on my end are starting at 2 – this was groping in the dark diagnostics and issues such as no audio, CICs not in service when both sides claim they are, etc may point to misaligned CICs;
• make sure you have configured from-pstn or the appropriate context in yourextensions.conf.

Confirming Your Link Is Up

Now start wanrouter (/etc/init.d/wanrouter start); dahdi (/etc/init.d/dahdi start); and Asterisk (/etc/init.d/asterisk start). You should see your link come up via logs available with the dmesg command. Launch the Asterisk console and check the status of your links:

ast-deg1-1*CLI> ss7 show cics 1
  CIC   DPC  DAHDI        STATE   BLOCKING
    2    3      2         Idle
    3    3      3         Idle
    4    3      4         Idle
    5    3      5         Idle
    6    3      6         Idle
    7    3      7         Idle
    8    3      8         Idle
    9    3      9         Idle
   10    3     10         Idle
   11    3     11         Idle
   12    3     12         Idle
   13    3     13         Idle
   14    3     14         Idle
   15    3     15         Idle
   16    3     16         Idle
   17    3     17         Idle
   18    3     18         Idle
   19    3     19         Idle
   20    3     20         Idle
   21    3     21         Idle
   22    3     22         Idle
   23    3     23         Idle
   24    3     24         Idle
   25    3     25         Idle
   26    3     26         Idle
   27    3     27         Idle
   28    3     28         Idle
   29    3     29         Idle
   30    3     30         Idle
   31    3     31         Idle

You should now be okay to make test calls.

Do You Need Professional Support / Consultancy?

While I will try to respond to comments and questions on this blog, I don’t have the time to provide one on one assistance pro-bono. Professional consultancy on Asterisk and SS7 is available worldwide through my company, Open Solutions with contact details here.

References

For posterity, I have added Domjan Attila patched libss7 and chan_dahdi to GitHub:

• https://github.com/barryo/attila-libss7
• https://github.com/barryo/attila-libss7-chan_dahdi

To that end, I have created a repository on GitHub for the task with a detailed readme file:

• https://github.com/barryo/nagios-plugins

As a starting point, there are four plugins available now:

The straw finally came when Nick forced my hand for a project we wanted to release through our work in INEX. I was pushing for Google Code but he had his heart set on GitHub. Now, in fairness, GitHub has some SVN bindings but after some research, I decided to dive right in.

Now, there’s both a steep learning curve but also a complete change of mindset required from centralised source code management (SCM) with SVN to the distributed model of Git. In the end, most projects will decide on a canonical Git repository anyway which pushes you slightly back towards centralised but there’s still a world of a difference.

So, what’s so good about Git? Well, lots. But first and foremost is it’s exceptionally powerful yet simple branching and merging that just works. And works fast – remember, with Git everything is local.

One work flow that used to kill me in SVN was that you’d be implementing feature X but someone needed bug Y fixed immediately involving some of the same code. Getting just the fix for Y in was tough and complicated. And branching in SVN isn’t quick or simple. In Git, I branch from the main development branch for every new feature, bug fix, etc and then merge what I need between them and back into develop when they’re ready to be pushed back to the agreed canonical repository.

I’ve been so impressed with Git that I’ve moved an open source project we created in Open Solutions over to Github: ViMbAdmin. I’ve also forced the rest of my team in Open Solutions over to Git and migrated a number of customer projects already. And we’re reaping productivity rewards!

How we work Git for projects was taken from this excellent post which I would fully recommend: A successful Git branching model.

Useful Git Links:

• Git for SVN Users: http://git.or.cz/course/svn.html
• Git SVN Comparison: https://git.wiki.kernel.org/index.php/GitSvnComparison
• Git’s own website: http://git-scm.com/
• Git Cheat Sheets: http://help.github.com/git-cheat-sheets/
• The excellent book Version Control with Git (from Amazon)

The RB750 and the RB750G are two identical looking routers intended for the SOHO environment:

The specifications for the RB750 (with differences for the RB750G in italics and parenthesis) are:

• five FastEthernet 100Mbps (Gigabit 1Gbps) ports;
• 32MB DDR SDRAM ;
• 64MB on board NAND storage;
• Atheros AR7240 400MHz (AR7161 680MHz) CPU;
• powered by PoE or power jack;
• up to 3W (6W) power consumption;
• ports 2-5 share dedicated switch chip allowing full 100Mbps (1Gbps) throughput;
• all ports can be individually configured.
• €31.73 (€54.61) from Wireless Connect.

Both routers come with an L4 license of Mikritik’s RouterOS which is built on the Linux kernel so anyone familiar with Linux networking will get up to speed on these boxes in no time.

As a disclaimer in case it is not clear, all routing tests are done using just two ports – one for the traffic generator and one for the receiver – with the device under testing routing the packets between two networks. As such, on the RB750, the maximum throughput we could achieve would be 100Mbps.

I ran tests for plain routing and also, in evaluating it for certain uses, over a VPN tunnel.

All results are presented below. Given the wealth of features, I think these are super boxes at a super price. So far I’ve put them on the end of an Imagine DSL line providing IPv4 and v6 over PPPoE and the end of a 30Mb UPC line taking its UPC IP via DHCP. They provide firewall, NAT, port forwarding, OpenVPN tunnels, QoS, DHCP, DNS caching and VLANs for phone / VoIP and managment networks.

Following the conference I picked up some RB750′s and RB750G’s and was very impressed. So much so, that I picked up a RB1100 also. The RB1100 specifications include:

• 13 individual 1Gbps ports;
• 2 x 5 port switch groups;
• 800MHz Power PC MPC8544E processor;
• SODIMM RAM slot with up to 1.5GB RAM;
• 1 x microSD card slot;
• 1U rack mount case.

I decided to benchmark this to see at just what rate it could route packets.

Benchmark Methodology and Tests

I used two PCs running Linux with iperf to measure TCP throughout with different packet sizes. To establish a baseline, I ran the same tests with the two PCs directly connected (this is the Direct Connection results below). The maximum achievable result with this is 1Gbps.

An example command line for the test which runs for 10 secs by default and for a packet size of 64 bytes is:

iperf -f m -i 1 -c 10.0.0.1 -l 64

Then I ran four test sets routing traffic between two networks as follows:

1. No c/t, no f/w: connection tracking disabled and firewall set to allow all;
2. No c/t, f/w: connection tracking disabled but with some simple firewall rules;
3. C/t, no f/w: connection tracking enabled but firewall set to allow all;
4. C/t, f/w: connection tracking enabled and stateful firewall rules.

In addition, I ran the above four tests with the RB1100 configured as a OpenVPN server:

/interface ovpn-server serverset auth=sha1,md5 certificate=cert1 \
cipher=blowfish128,aes128,aes192,aes256                          \
default-profile=your_profile enabled=yes                         \
keepalive-timeout=disabled mac-address=FE:50:A7:D5:FE:B7         \
max-mtu=1500 mode=ip netmask=24 port=1194                        \
require-client-certificate=no

One of the PCs was connected to the RB1100 as a VPN client pushing traffic to the other server on a non-VPN connect with all traffic routed through the RB1100. I also did a baseline test by running the VPN server with the same encryption on one of the PCs with a direct connect to the other and then pushing traffic over the VPN link.

Results:

The results can be seen in the following graph:

Without connection tracking and firewall, full line rate is achievable for packet sizes of 256bytes and higher – all in all, an excellent result. That said, no connection tracking and no firewall would be an unusual configuration and with these, the box maxes out at around 525Mbps – still an excellent result for less than €400.

The VPN tests yielded:

VPN throughput primarily relies on CPU horse power and the PCs used for the Direct Connection baseline test are pretty modern.

Head over to my article on the company blog for the tips.

http://brainsongimp.blogspot.com/2008/03/black-and-white-jpg-to-transparent-png.html

There’s a good how-to here:

http://www.inteller.net/notes/change-user-id-on-snow-leopard

Cannot find autoconf. Please check your autoconf installation and the
$PHP_AUTOCONF environment variable. Then, rerun this script.

and when fixed, it’s followed up by:

Cannot find autoheader. Please check your autoconf installation and the
$PHP_AUTOHEADER environment variable. Then, rerun this script.

The fix is to set those environment variables (as appropriate for the autoconf and autoheader version numbers – the below is my example on FreeBSD 8.1):

export PHP_AUTOCONF=/usr/local/bin/autoconf-2.68
export PHP_AUTOHEADER=/usr/local/bin/autoheader-2.68

in bash of the following in tcsh:

setenv PHP_AUTOCONF autoconf-2.68
setenv PHP_AUTOHEADER autoheader-2.68

alias 2fm='cvlc http://dynamic.rte.ie/av/live/radio/2fm.asx'
alias newstalk='cvlc http://newstalk.fmstreams.com:8008/listen.pls'
alias rteradio1='cvlc http://dynamic.rte.ie/av/live/radio/radio1.asx'
alias todayfm='cvlc http://audiostore.todayfm.com/audio/todayfmIRL_64K.asx'

UPDATED 2011-02-07: 2FM added.