CX-U Redundancy Features v2

CX-U Reliability Features: Meeting Service Provider Requirements Draft Revision 1 – May 2007
CX-U Reliability Features:
Meeting Service Provider Requirement
Andre Houde,
Director, Product Management
©2007 – Memotec Inc. Page 1

CX-U Reliability Features: Meeting Service Provider Requirements Draft Revision 1 – May 2007
Revision 1 – May 2007
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Disclaimer:
Please, note that some statements contained in this paper are forward looking, and that some of the features
described herein may not be available at the current time of ordering the product. Please, consult a Memotec
representative for more information.
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CX-U Reliability Features: Meeting Service Provider Requirements Draft Revision 1 – May 2007
1. Standalone system
The standalone CX-U system is made of a single 1U chassis system. It does not offer 1+1
system redundancy and zero downtime serviceability. However, it offers a built-in impressive list
of reliability features which already delivers a very high availability rate level and puts this
standalone configuration system heads and shoulder above the competition in terms of network
downtime and serviceability. As a matter of fact, many operators have chosen to deploy
Memotec’s CX-U in standalone configuration, although we also offer the CX-U in an affordable
fully redundant 1+1 configuration system.
Hereafter is a detailed list of the CX-U reliability features:
a) High MTBF:
The design of the CX-U has been done since day one with reliability and serviceability in
mind.
Components have been carefully chosen for their MTBF and support of extended
temperature range [0 up to 65C], thus increasing the life time of the system and
decreasing chances of failure. Result is a compounded MTBF of over 12 years.
The CX-U also boasts ultra low consumption (

CX-U Reliability Features: Meeting Service Provider Requirements Draft Revision 1 – May 2007
c) Network trunk protection
The CX-U offers various mode of network trunk or network uplink protection mechanisms.
Those include:
- 1:1 link protection (active / backup). The protected interfaces may or may not be of the
same nature. For example, it is possible to protect the main network uplink via a backup
network of different nature and using a different physical interface with different capacity
(For example, backup of a digital E1 uplink connected to a PDH transmission network via
a satellite link backup connected to a modem via a serial interface or IP/Ethernet
interface). Traffic protection and priority mechanism allows to protect or prioritized only
the most important traffic (for example, signaling, voice services) in case the backup link
has a significantly smaller capacity than the main link.
- 1+1 link protection. In this configuration, both uplinks are active and carrying traffic. The
uplink traffic is duplicated on both links: if one link fails, the traffic is still being carried
through without any loss of information or service interruption.
- 1+1 link protection with load sharing. In this configuration, in normal operation, the traffic
is sent other the two links, using the full offered transmission capacity. If one of the link
fails, then all the traffic is sent to the remaining active links. Traffic priority mechanisms
are used to protect the most important traffic in congestion situations.
- Network protection with re-routing. In this configuration, standard dynamic IP routing
mechanism (OSPF) is used to re-reroute the traffic around the outage in the backhaul
network;
- Dual hosting {host protection}: in an IP network environment, the VRRP protocol is used
to connect the CX-U to two network router hosts, assuring not only link protection, but
also the host router equipment protection.
d) Line By-Pass
The CX-U allows to protect selected digital T1/E1 bearers in case of total system failure
(hardware failure, software lock, power down). In this configuration the bearer and the
network uplink are short-circuited using static relays in case of system failure. Specific
mechanisms ensure the good operation of the system end-to-end, and the switchover of
a system from active to line bypass. The detection of the status of the system at the
remote end is automatic, from active to bypass and back. Switchover from active to line
bypass occurs in less 100ms, and without service interruption (no loss of connection, no
call drops). The line bypass mechanism also works over satellite links.
©2007 – Memotec Inc. Page 4

CX-U Reliability Features: Meeting Service Provider Requirements Draft Revision 1 – May 2007
Figure 1: CX-U backplane with Line Bypass and 75 Ohms BT43 E1 connectors
Note that some restrictions apply: line bypass only works if the network uplink is a digital
E1 or T1, and only some of bearers can be protected, depending of the number of T1/E1
uplinks and the system model – 2 for the CX-U 1010 and 4 for the CX-U 1240.
©2007 – Memotec Inc. Page 5

CX-U Reliability Features: Meeting Service Provider Requirements Draft Revision 1 – May 2007
2. Redundancy system
The CX-U is also available as a true 1+1 (hot standby) redundant system, as per BellCore
specifications. 1+1 means that the two units are active and process the whole network traffic
equally, but only one unit (the active one) send the traffic on the interface. Both machines are
therefore in the same state and supporting the same configuration. If one system fails, the other
unit takes over, switch off the interfaces of the failed unit, and become the active unit sending the
traffic to the bearer and network links.
Figure 2: CX-U Redundant System configuration and backplane
Switchover occurs in less than 50ms, thus without any service interruption (loss of connections or
call drops).
The system automatically reset itself and full redundant system restoration is automatic: the units
are able to switch back and forth without manual intervention, and without service interruption.
Specific mechanisms ensure the good operation of the system end-to-end. The redundancy
mechanism operates as well on terrestrial links (microwave, leased lines) as on satellite links.
In terms of connectivity, the system offers a true 1+1 configuration with integrated A/B switch: no
additional Y cable or external additional specific device is required. The line cables directly
connect to the redundant system backplane with a standard single connector. Also, each of the
system unit can be removed for repair, maintenance, or upgrade purpose without service
interruption and without disconnecting the cables.
The physical interfaces protected include digital T1/E1 links (bearers and network uplinks), and
Serial interface. Ethernet connection are protected though using the VRRP mechanism.
©2007 – Memotec Inc. Page 6