Akara's OUSP 2000 Goes the Distance With Fibre Channel

The OUSP 2000 supports up to two Sonet interfaces in any combination of OC-3, OC-12 or OC-48. The unit also supports up to six standard GBIC (gigabit interface converter) interfaces for Gigabit Ethernet or Fibre Channel connectors. Akara supplied me with two OUSP 2000s, both with an OC-12 and an OC-48 interface. On the local side, Akara installed two gigabit Fibre Channel and one Gigabit Ethernet GBIC.

Configuring the units was straightforward, though I had to come to grips with some new terms. The OUSPs first needed to be assigned IP addresses. With those in place from a serial connection, the units could then be accessed via Akara's management software, called OUSM (OUS Manager) 7000, which I ran from a Windows 2000 system.

The first new term I had to learn was virtual facility, which Akara uses in reference to the physical Sonet connection between the OUSP units. The virtual facility defines the point-to-point connection between two OUSP 2000s and the bandwidth available to that connection. In my case, two virtual facilities were defined--one for the OC-48 and one for the OC-12. You need to define the virtual facilities initially, or if your Sonet connection changes.To move traffic across the OUSPs, you must create a service circuit between interfaces on the units. Regardless of whether you are using Gigabit Ethernet or Fibre Channel, the setup is similar: Define the interfaces to be used at either end of the connection and the bandwidth to be used between them. The connection can be set up symmetrically or asymmetrically, and can be defined by the number of STS (synchronous transport signal) or STM (synchronous transfer module) channels or in megabytes.

The bandwidth used can be created as reserved, unpreemptable or preemptable. Reserved creates bandwidth that can't be used by anyone else and will fail over in case of outage on the primary fiber. This obviously requires a second Sonet interface.

For my testing, I created a reserved Fibre Channel circuit and passed traffic over the circuit created from a Spirent Communications SmartBits 600 equipped with Fibre Channel and Gigabit Ethernet interfaces. Pulling the OC-48 connection on the unit caused the traffic to jump to the OC-12 connection. A few minutes after the OC-48 was reconnected, the OUSPs moved the traffic back from the OC-12.

Unpreemptable service sets aside bandwidth that is guaranteed just as reserved is, except it won't fail over during an outage. Preemptable bandwidth is best effort, can be shared by circuits and won't fail over.

Flow control can be set up on Ethernet or Fibre Channel connections but in each case performs different tasks. On Gigabit Ethernet connections with flow control turned on, the OUSP performs QoS (Quality of Service) on the circuit and allows priority traffic to be placed on the circuit first. When it's turned off, every packet is placed as best effort.Fibre Channel connections really show what the flow control is meant to do. Turned off, flow control creates the connection from one Fibre Channel device to the other. Turned on, it uses an extended reach feature that breaks the connection into three pieces -- two connections from both OUSPs to the Fibre Channel devices attached to them and one between the two OUSPs.

Go With the Flow

My testing showed that flow control must be turned on for two Fibre Channel devices attached over even a few kilometers. At a distance of 75 km with flow control on, I was able to achieve data rates as if two OUSPs were connected with just a 10-meter fiber connection. In throughput tests from less than one kilometer and up to 75 km, the data rate remained the same regardless of the distance when flow control is turned on.

Akara has built into its OUSM software a complete set of reporting capabilities, including many functions that typically would be found only on a traffic analyzer. Beyond the normal error logs and details, the OUSM 7000 software can also display usage based on service circuit or virtual facility. It displays bidirectional data so both sides of the connection can be monitored along with errors. Polling intervals can be set in seconds and the duration can be specified if you want to monitor the connection for a set amount of time.

Alarms are noted by severity from the main screen of OUSM and are listed by category according to what is in alarm: virtual facility, virtual facility group, system, equipment, service circuit or customer.Both the OUSP and the accompanying OUSM software performed well, but they aren't without their faults. The OUSP has no Fibre Channel switching abilities built in. If you have two offices trying to access a Fibre Channel array at a third office, the OUSP at the third office will need to dedicate two of its six GBIC interfaces to accessing the array. This could cause a problem if more than six offices needed to access an array. The same is true of Ethernet connections. Each GBIC port on an OUSP is dedicated to a particular point-to-point connection and can't be shared. I also found some oddities with the OUSM software.

While the software is smart enough to make sure that enough bandwidth is available on both Sonet fibers when creating a reserved connection, it isn't smart enough to keep you from wasting bandwidth. The OUSM software would allow me to create a 2-Gbps connection for a single Gigabit Ethernet GBIC. I expected it to top out and not let me create a service circuit larger than the GBIC interface, but it did. An experienced person wouldn't do this in the first place, but a less savvy tech could easily waste bandwidth.

Darrin Woods is a Network Computing contributing editor. He has worked as a WAN engineer for a telecom carrier. Send your comments on this article to him at [email protected].