Storage over existing Low Speed Channels

July 21, 2008 - PRLog -- . Introduction and Scope:
Tremendous growth in storage and computer processing needs, created demand for reliable and cost effective back up and data protection solutions for the enterprise. Hence, there is a growing public awareness to the need for business continuity and disaster recovery solutions.  
In this paper, we present a new and innovative approach for carriers and enterprises to use the low rate SONET/SDH channels (Nx1.5Mb/s, Nx2Mb/s) as the WAN between SAN islands. We describe the advantages of using low rates over SONET/SDH from the user perspective and compare it to using the IP network.
A typical deployment using low rate channels within the SONET/SDH is depicted in Figure-1. Primary SAN Island is connected to another SAN Island using PacketLight products. The PL-10/20/100 is connected to the adjacent ADM using an STM-1 connection that is partly populated by 2Mb/s channels. The PL-10/20/100 can concatenate any number of 2Mb/s channels to form a fat pipe of 2-155Mb/s.
This is using the latest GFP/VCAT low order concatenation standards. The carrier will charge the enterprise only for the bandwidth that is consumed within the network and not for the whole STM-1 pipe. This mode of operation is customary for Ethernet services and is now tailored for FC services.

Figure-1: PacketLight Storage over SONET/SDH access devices for disaster recovery applications



2. Why Nx2Mb/s SONET/SDH as a Solution of Choice ?
There are four main reasons why customers will choose to use this solution:
•   Affordable cost of communications – Cost of bandwidth in the WAN dictates to customers the use of economical solutions. Nx2Mb/s is low rate compared to the 1Gb/s of the FC interfaces, but it is enough in many cases for Small-Medium Businesses (SMBs) to create a data replication solution. The 2Mb/s granularity is well known to carriers and it is the most popular solution in the market.

•   Reliability – Unlike IP/Ethernet networks the SONET/SDH network provides a secure, dedicated and guaranteed bandwidth connection to customers. The public SONET/SDH network is available nearly at any business location. The operation of the SONET/SDH network is very reliable due to stringent equipment design standard and redundant planning based on known and reliable protection schemes.  Operational Support Systems for the monitoring and activation of services are in place as well as the trained manpower. Carriers are keen to utilize the network for additional data services and enterprises are keen to outsource the operational task of maintaining the reliable link to carriers. This creates a win-win situation. IP networks typically suffer from Bit Error Rates and changes in the throughput as well as being a security challenge.

•   Effortless Scalability  – using the latest standards of Virtual Concatenation (VCAT) – customers can start with as low as 2MB/s and grow gradually as they can afford. Both the carrier and the customer need not make any changes in the installation except a single remote command operation to change the bandwidth. This is done in seconds. Customers can now grow from data replication solutions that require minimal bandwidth to synchronous solutions that require 155mb/s using the same fiber and the same customer located equipment.

•   Fiber Channel Distance Extension - The standards provide means for extending the distance between the main sites and the back-up sites. SONET/SDH can be used in cases where hundreds (and even thousands) of kilometers are separating the sites.


3. Storage over SONET/SDH with Nx2Mb/s – Product Support





PL-100  Multiple Storage Extension over SONET/SDH



PL-10 & PL-20  Storage Extension over SONET/SDH

PacketLight's PL-10/20 provides the support for NXVC12/VT1.5  PL-10/20 provides a single FC interface towards the SAN island switch and an STM-1/4 OC-12  (optionally 1+1 protected) towards the SONET/SDH network. It has also an optional dual power supply- AC or DC. It supports also LCAS, which means that if there is a failure of one of the 2M channels it can reduce the bandwidth without any bit loss.
PacketLight's PL-100 can be used over existing SONET/SDH infrastructures, DWDM networks, and dark fiber, utilizing the new standards of Generic Framing Procedure (GFP), Virtual Concatenation (VCAT), Link Capacity Adjustment Scheme (LCAS) and FC-BB.  Designed primarily as an access/transport device, the PL-100 is typically deployed as CPE in enterprise campus environments or at Central Sites.  The PL-100 can also be used as a complimentary solution to MSPPs, Metro DWDM, and Ethernet Networks. It can multiplex several Data and Storage services into a protected OC-48/STM-16 single wavelength and maintain the FC throughput over distance.
The PL-10/20/100 nodes are using the standard FC-BB-2_SONET mapping of FC over SONET/SDH.  The PL-10/20/100 is remotely managed via the DCC link of the SONET/SDH link or via the 10/100BT Ethernet port.

4. Summary:
The use of SONET/SDH NxVC12/VT1.5 for Business Continuity, Disaster Recovery and Data Replication applications suits a large number of enterprises and provides technical and business benefits:
   Small Footprint (1U)
   Low communication costs
   High reliability
   Secure dedicated connections
   Effortless scalability from 2-155Mb/s
PacketLight's PL-10/20/100 Family is based on the latest GFP/VCAT and FC-BB standards and is positioned for use by service providers and enterprises as CLE Next Generation SONET/SDH device. Enterprise can benefit from the existing reliable carrier networks and use the carrier as a one-stop-shop for their storage requirements.

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PacketLight Networks Ltd develops a complete set of CWDM, DWDM and dark fiber solutions. PacketLight customers are carriers, service providers,