Table Of Contents
Application Note
Taking Advantage of Embedded Network Bandwidth with
Protection Channel Access
on the Cisco ONS 15454
Maintaining profitability and reducing costs are the focus in today's challenging market environment. Cisco Systems helps customers achieve these objectives by offering the embedded bandwidth and dependable technology on the Cisco ONS 15454 SONET and SDH Multiservice Provisioning Platforms (MSPP).
BackgroundMarket conditions in the telecommunications sector as well as many others have changed, and service providers and enterprise companies now focus on making profitability gains from incremental investments in smart technology.
Hundreds of companies have deployed the Cisco ONS 15454. These companies are benefiting greatly from the industry-leading capabilities of this revolutionary platform, which delivers scalable transport bandwidth, multiservice interface support (DS-n/E-n, OC-n/STM-n, 10/100/1000-Mbps Ethernet, and more) matched to the metro market needs, simplified engineering and operations to lower technician training costs, and a competitive initial-cost model.
The Cisco ONS 15454 is built on a dependable Synchronous Optical Network (SONET/SDH) foundation, protocols used by all telecom service providers worldwide, helping to deliver the reliability and class of service now expected from voice networks. The addition of PCA enables the service providers to better utilize their network bandwidth to improve their overall profitability.
What is Protection Channel Access (PCA)?SONET 2-and 4-fiber Bidirectional Line Switched Rings (BLSRs) as well as SDH 2-and 4-fiber Multiplex Section Sub-Network Protection Rings (MS-SPR), provide extreme resilience by reserving "protection" bandwidth for active circuits. This "protection" bandwidth sits idle until called upon by a network event that affects the "working" service path. PCA allows the "idle" protection bandwidth to be used for carrying traffic. (It does not provide physical-layer protection on the protection bandwidth.) PCA is a well-understood technology, and its implementation is documented by Telcordia in GR-1230-CORE, section 3.4 Extra Traffic ( http://www.telcordia.com) and by the International Telecommunications Union in ITU G.841 ( http://www.itu.org). Users can be confident in deploying the robust PCA technology.
A Mix of Protocols Is KeySONET/SDH are the technology of choice for service providers and many large enterprise networks. However, large-scale deployments of PCA have been greatly limited by the need to understand how to best take advantage of the technology. The key to delivering additional revenue and reducing costs from deployed BLSR SONET or MS-SPR SDH bandwidth is understanding how to design a PCA network using both PCA and protected circuits along with higher-layer protocols (such as IP, Ethernet, MPLS fast-rerouting, Gigabit EtherChannel® (802.3ad), Spatial Reuse Protocol (SRP), Resilient Packet Ring (RPR)/Dynamic Packet Transport (DPT), fast Spanning Tree, and QoS). This technology coupling allows service providers and enterprises to meet application requirements for network availability, downtime, bandwidth, and cost. Depending upon the applications and network topology, implementing IP-PCA can potentially increase revenue up to 75 percent from a deployed service provider transport network. Enterprise customers can see network cost reductions of 30 to 50 percent through improved bandwidth utilization. These increased revenues and reduced costs require negligible capital investment, yielding significant financial benefit to both service providers and enterprise customers. Additionally, service providers gain a competitive advantage by using IP-PCA to offer reduced tariff packages to existing customers, and available bandwidth to potential new customers.
Applications for PCASome applications of PCA technology include:
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Service provider networks
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Technologies to Use with PCAPCA can be used in conjunction with the EtherChannel protocol as an implementation option. The EtherChannel protocol (802.1ad) allows the creation of a larger bandwidth interconnection using two or more individual interfaces. For example, Gigabit EtherChannel enables up to 8 Gigabit Ethernet interfaces to be coupled together to act as a logical 8 Gbps interface. The 802.1ad protocol provides network resiliency support by rebalancing data traffic across all interfaces in the event that an individual interface is rendered inoperable.
Figures 1 and 2 depict the interaction of the SONET 2F-BLSR with the Gigabit EtherChannel protocol. By using protected and PCA bandwidth on the 2F-BLSR networks along with Gigabit EtherChannel and Ethernet 802.1p priority tags, the network supports a wide range of customer applications with a solution that can provide:
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This is just one example of how protocols can be combined to better take advantage of the capabilities of an installed 2F-BLSR network. Implementation of PCA technology in a SDH environment is analogous over 2 and 4-fiber MS-SPR networks.
Figure 1
Using PCA with Gigabit EtherChannel (Normal State)
Figure 2
Leveraging PCA with Gigabit EtherChannel (Protection State)
Sample Service Provider Business CaseUtilizing the PCA bandwidth of a BLSR or MS-SPR network enables the service provider to sell bandwidth that, in effect, has a zero-cost base. Once installed, the network is assumed to have a fixed cost. Thus, the addition of PCA bandwidth adds incremental revenue (new circuits can be sold) for little incremental cost (of upgrading to a new software load).
Figure 3 shows a service provider network with the Cisco ONS 15454 installed, using two fiber BLSRs at an OC-48 optical line rate. The service provider's customer is looking to mesh a four-switch network over the service provider's network.
Figure 3
Example Network
The interface between the customer switches and the service provider's Cisco ONS 15454 transport network are via Gigabit Ethernet interfaces. The service provider bandwidth charges (tariff) per month are outlined in Table 1. Additionally, the assumed price of an OC-48 based, two-fiber BLSR Cisco ONS 15454 with the appropriate Gigabit Ethernet interfaces is $96,000.
Table 1 Service Provider Circuit Pricing (Tariff) per Month
Protected Bandwidth
$7,500
$3,750
PCA Bandwidth
$3,750
$1,875
Protected-Bandwidth-Only Network Example (no PCA)With the above networking assumptions, if the customer requests to mesh their switch network using fully protected, Gigabit Ethernet bandwidth, which requires an STS-24 circuit, the total circuit price the service provider would charge is $45,000 per month (6 x $7500/STS-24 protected bandwidth circuit). To meet the customer's request, the service provider would require an OC-48 network consisting of three rings of four nodes with a total cost of $1,104,000 (12 nodes x $96,000/node), as depicted in Figure 4.
Figure 4
Service Provider Network without PCA
PCA-with-Protected-Bandwidth Network ExampleThis example uses the above network assumptions, with an additional customer request to mesh a switch network using a combination of fully protected bandwidth and PCA bandwidth utilizing rate-limited 600 Mbps Gigabit Ethernet circuits. With each circuit requiring an STS-12 bandwidth, the total circuit price the service provider would charge is $33,750 per month (6 x $37,500/STS-12 protected bandwidth circuit + 6 x $1875/STS-12 PCA bandwidth circuit). To service this request, the service provider would require an OC-48 network consisting of two rings of four nodes with a total cost of $736,000 (8 nodes x $96,000/node), as depicted in Figure 5.
Figure 5
Service Provider Network with PCA
Network Example ComparisonTable 2 compares the above scenarios, showing the advantages of using PCA bandwidth for both the service provider and the service provider's customer.
Table 2 shows how the service provider's customer can enjoy a 25 percent reduction in their monthly networking bill. The service provider reduces their capital expenditures by 33 percent, while expediting their ROI by three months, from 25 to 22. An additional benefit to the service provider is the increased value of the remaining network bandwidth. The ability to sell another 100 percent of the BLSR network opened up by PCA deployment, even at reduced circuit prices, significantly improves ROI and increases capacity for additional customer traffic.
Other benefits to using the PCA function include:
Service Provider Benefits
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Customer Benefits
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PCA used with higher-layer protocols opens up new revenue-generating service tariffs and improves overall profit margins.
ConclusionCisco provides the tools and products to deploy a cost-effective, multiprotocol networking solution, allowing greater network profitability and cost savings. Taking advantage of the powerful capabilities of the Cisco ONS 15454 SONET and SDH platforms enables a service provider or enterprise to build a robust, highly scalable, cost-effective networking solution. Upgrading a Cisco ONS 15454 network element to support PCA can be accomplished remotely and while in service, saving the cost of deploying technicians to remote facilities. Additionally, the Cisco ONS 15454 BLSR or MS-SPR networks deployed today, whether OC-12/STM-4, OC-48/STM-16 or OC-192/STM-64-based, are positioned to take advantage of PCA benefits.
