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Keymile's NEBRO: Now Ethernet Gets a Free Ride Over SDH and SONET Networks
[January 31, 2006]

Keymile's NEBRO: Now Ethernet Gets a Free Ride Over SDH and SONET Networks

By Biju Oommen
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When you look intently at the communications landscape you will see that the Ethernet LAN serves our internal networks while Synchronous Optical Network (SONET) or Synchronous Digital Hierarchy (SDH) serves carrier and service provider networks. For inter site communication end users relied on Asynchronous transfer mode (ATM) or packet over SONET or frame relay technologies as SONET and SDH channel sizes were defined to support legacy TDM based DS1, DS3, E1, E2 signals and Ethernet was not directly supported. All of this meant that there was additional equipment and network management adding to the cost and complexity.

The scene now is changing and carriers have to transport and deliver broadband Ethernet services. Thanks to technologies like virtual concatenation (solves bandwidth mismatch problems by combining several VC12 or VC3 to create a high bandwidth link between two sites on a SDH network), Link Capacity Adjustment Scheme (LCAS-protocol for adding or removing bandwidth seamlessly without affecting traffic ) and Generic Framing Procedure (GFP- method used to encapsulate and transport data like variable Ethernet MAC frames over SDH networks) it is now possible for SONET and SDH based networks to efficiently transport slices of Ethernet traffic and IP services to various customers.

Carriers possessing a network infrastructure of voice-optimized SDH networks can now implement Ethernet over SDH (EoS). This translates into numerous benefits for carriers and their subscribers. They can offer bandwidth on demand, provision data rates as per end user requirements; offer carrier infrastructure associated reliability thanks to inherent fault recovery mechanism, dynamic load balancing, and dynamic route optimisation and provide broad service area coverage. They can offer new services like private Ethernet leased line or virtual private Ethernet leased line connectivity between end user sites, point to point or multipoint through the currently deployed SDH network.
One such EoS offering is from Keymile. It is  called the NEBRO and the NEBRA, plug in modules for transporting and switching Ethernet data over the incumbent SDH network. Keymile has provided these modules on their proven carrier grade multi service access platform called UMUX. They have made sure that carriers using this platform can maintain revenue streams from their existing voice services and simultaneously deliver new broadband Ethernet services on their current SDH infrastructure.
If you have one versatile multifunction platform then it certainly makes the carriers happy as they are looking for ways to reduce CAPEX and OPEX. These units for transport support VCAT, GFP, and LCAS. For Ethernet switching they support  virtual local are network (VLAN) switching, VLAN tagging or pass-through as well as VLAN tag stacking and rapid spanning tree protocol (RSTP).In traffic prioritisation you get four class of service (CoS) per port.
For ports the NEBRO unit is equipped with the standard plain vanilla type four UTP RJ-45 10/100 Base-T interfaces and two cages which can accommodate plug-in multisource agreement Small Form factor Pluggable (SFP) modules. These SFP modules could be of your choice for optical multi-mode or single mode fast Ethernet or Gigabit Ethernet connections.
The NEBRA is an all optical SFP solution with six SFP cages for a selection between six optical fast Ethernet or four fast Ethernet and two gigabit Ethernet connections. The capacity is 63 x VC12 or 3 x VC3 level with virtual concatenation at VC12 or VC3 levels.     
Operational Testing
My test bed for testing EoS was a pair of UMUX 1500 chassis slotted in with the required SYNIO (optical STM-1) and NEBRO (EoS) modules accompanied by two Cisco 2950 Ethernet switches. I used Keymile’s MS windows based graphical UMUX configuration software tool (UCST) for configuration and error management.
The whole setup of NEBRO is actually very simple if concepts on SDH and Ethernet switching are clear at the outset. I started by selecting the switching and transport function for NEBRO. Then I set the Ethernet physical layer port parameters such as IEEE 802.3 flow control, LAN mode etc. Configuring the transport meant setting EoS parameters like member type (VC12 or VC3), number of members, enabling LCAS and setting the VC12 or VC3 parameters for the port. Going on to the switching part I set the port VLAN ID, port priority, Tag stacking (selectable are disabled, port VLAN ID/Tag priority, port VLAN ID/port priority), the Ethernet queuing profile was set as strict. Under VLAN I configured the VLAN ID, assigned ports for that VLAN, enabled VLAN tagging for that port .In RSTP I left the Ethernet Bridge related parameters at default. I configured the cross-connects and the Ethernet leased line was setup between two sites. At both ends computers linked to the deployed Cisco 2950 Ethernet switches exchanged traffic effortlessly through NEBRO via the test EoS network. 
I found the status and maintenance function on the UCST for the NEBRO module to be very useful. It aided me in gathering information like state, link state, mode, operational state, up/total members, RSTP state etc.for the Ethernet physical, transport and switching functions of the NEBRO. The documentation on the CD proved to be very valuable during installation and configuration.
I have to say that the NEBRO plug in module met my connectivity objectives and thus garnered full marks as an EoS solution.
Nothing much except that I would like to see more application examples listed in the documentation.
By using the NEBRO module Keymile can satiate carrier Ethernet cravings of operators already using Keymile’s UMUX platform. The operator can aggregate multiple traffic types – Ethernet and legacy TDM – from multiple enterprise sites and thus maintain revenues from both Ethernet and legacy telephony services. 
Biju Oommen is a Telecommunications & Networking Solutions Consultant with a special focus on enterprise products and solutions.

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