Unexicon was originally started as a
vehicle for trying out OpenSS7 software without having
to go through the trouble of loading a system and getting it running.
It grew into a custom spun Linux distribution for
Following are some of the design decisions that we made along the way:
- Choice of Base Distribution
- We began the original work with live distributions based on
Slackware. The first problems encountered were
that Slackware did not support up to date kernels
that were capable of compressing and packaging a live system.
Most derivatives such as Slax and Salix
were rolling their own kernels to support the live distro.
- Gentoo was considered briefly. Very briefly.
Sabayon is a good live distro, but building
current packages is too much work.
- Spins based on RedHat were ruled out because the
software included in the Enterprise versions is too out of
date, there are too few supported software packages, and
their kernels are obsolete.
- Spins based on Debian were ruled out because
Debian has too long a release cycle and the
stable repositories are not up to date.
- Others were considered, but ultimately we landed on
Arch Linux. Arch is a popular
mainstream release, is a rolling release and always up
to date, supports a long-term-support kernel (3.0 series),
is easy to build packages for, has an accessible community
and user software repository, and are responsive to bug
reports. We had to ride the systemd upgrade, and
the upgrade from 2.6.32-lts to 3.0-lts kernel upgrade, but
aside from that it is a powerful, fast and stable server
- Design Principles
- To support a telecom spin, the system needed:
- Carrier-grade reliability and stability.
Linux itself is reliable and stable. We have servers here that
have wrapped their uptime clocks (>4 years uptime). The
source of problems is usually heat and friction. So we designed
a hardware platform that has no moving parts, is convention
cooled and has <60W TDP: wide open. 48VDC power and NEB-3
compatible chassis rounds out the solution. Check the
Hardware page for the solution.
- Self-organizing fault-tolerant clustering.
Clustering is difficult for designers to understand at the best
of times. Operators are often confused by the approaches. We
wanted self-configuring clustering. We started with the
spread toolkit, but it required static configuration
tables for which we would have to write reams of manuals. We
ported forward the ISIS toolkit, but eventually landed on a
distributed, fault-tolerant state-machine approach based on
reliable broadcast/multicast with a wacamole style
approach for IP pooling and takeover. Nodes discover the group
and join in a role. Failed nodes are identified quickly
(<25 ms) and their load is redistributed over the pool.
Management stations discover the pool and can provide visualization
of its operation. Nodes can be taken offline by simply yanking
- Full online checkpoint and rollback for software upgrades
to deployed systems.
Few distros understand this concept. When all of your revenue
is running through a set of boxes, downtime due to failed software
upgrades is intolerable. By having our own distro, using the LVM
(Logical Volume Manager) and the longstanding ability to snapshot
volumes, we have accomplished full checkpoint and rollback of the
system image, independent of the application (subscriber) database.
It includes the ability to swing back and forth between the
check-pointed and upgraded systems until a commit decision can be
made. Offline backup and restore of the entire system image is
- Single build for both deployment servers and management
Linux helps out a lot here. Most distributions, including
Arch are equally suited to the server room as to
the desktop. The decision to use graphical login on the server
platform using light-weight window managers has allowed a common
software base. Each load is equally suited to use as a management
station as to server deployment platform. Live distribution on
bootable USB flash drives means you can have a management station
on your keychain.
- Automatic networking.
Most Linux distributions fall down hard when it comes
to automatic networking. They assume well configurated WAPs or
DHCP servers for automatic networking. They usually assume that a
user is there to configure them. Unexicon
differs in that all of the networking is built to be automatic and
self-configuring. The nodes will slave off of DHCP or NIS servers
for VLAN 0 traffic, but they form their own spanning-tree-protocol
bridged VLAN among themselves and manage their IPs on VLAN 557 through
cooperation. Nodes can automatically access centralized NOC centres
housing a single Unexicon management node
to provide automatic VPN access into the NOC. Firewalls, routing (RIP,
OSPF, BABEL, BGP), NTP, mDNS, DNS-SD, XDCMP, are all automatic with
no manual configuration required. Just plug them in and they find
- As little configuration as possible to avoid learning-curve,
training, reams of paper documentation, and other dead
The choice for graphical login on the server platform simplifies
much of the administration and management of the platform. Integrated
management stations that provide network visualization and targetted
management with self-documenting SNMP MIBs rounds out the solution.
All telcom modules are designed for near-zero-configuration. Nodes
joining a cluster obtain configuration information from the distributed
state machine. As much base Linux system adminstration
and Unix-based systems knowledge is leveraged as much as possible.
Although we will have documents for add-on modules, they will mostly
be descriptive. All management tools are a click away on the integrated
- Scale down and scale up.
Integration of the OpenSS7 STREAMS packages provides
for performance gains of up to 500% over a base kernel without the
packages. This allows low cost Atom, Cortex, Arm or other fanless,
low-power server boards to be used without sacrificing performance.
A server can be used to handle a couple of links or trunks or can
be used to handle the entire signalling traffic for a small country.
- Minimal capital cost.
By scaling down we scale up. A bare-bones platform can be as
cheap as $300; fully loaded, full blown systems, $1200. Anyone
can afford to buy one of these. And they scale up. Four systems
can replace two $4 million dollar STPs. But they are cheap enough
to hand out to your customers for legacy SS7 access or TDM to VoIP
If you notice some principle or objective that we have missed above,
drop us a note. See the Contact page.
© Copyright 2012, 2013 OpenSS7 Corporation. All rights reserved.