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A Network Administrator's View of Multiservice Networks

Chapter Description

Multiservice networks provide more than one distinct communications service type over the same physical infrastructure. Multiservice implies not only the existence of multiple traffic types within the network, but also the ability of a single network to support all of these applications without compromising quality of service (QoS) for any of them. This chapter covers multiservice networks in detail from the network administrator's viewpoint.

Multiservice Core and Edge Switching

Networking traffic continues to accelerate at the metro edge and aggregate into the metro core, from large enterprises driving Ethernet requirements into metropolitan area networks (MANs) to rising waves of broadband from small and medium businesses and consumers. In fact, the Ethernet opportunity within the service provider space is wide open, and providers of all types are counting on Ethernet services as a large part of their portfolio growth. While there is a demand shift from circuit to packet traffic within the MAN, the vast installation base of SONET/SDH service functionality precludes a forklift upgrade of metropolitan provider technology, instead requiring an evolutionary migration path to packet-based services from a SONET/SDH heritage.

Multiservice Provisioning Platforms (MSPPs) combine the functions and services of different network elements into a single device. For a few more years, voice traffic is predicted to remain the cash cow of provider revenues, making time division multiplexing (TDM) switching support an important requirement. The MSPP market is defined as new-generation provider equipment with SONET/SDH add/drop multiplexer (ADM) functionality, TDM and packet functionality, particularly Ethernet, and is deployed at the metro multiservice edge or core.

Multiservice Switching Platforms (MSSPs) are optimized for metropolitan core aggregation requirements, typically consolidating multiple discreet SONET ADMs and broadband digital access cross-connect systems (DACSs), while providing core switching services for multiple MSPP deployments.

Eliminating platforms, no matter how reliable, reduces the single points of failure in the overall network architecture. MSPPs and MSSPs integrate multiple device functions to allow consolidation of platforms while introducing new technology for services innovation.

MSPPs and MSSPs entered the market at the beginning of a long telecom winter in 2000. However, their inherent value proposition has weathered the fiscal storms and frozen budgets, finding favor first with emerging network providers and then moving into the incumbent provider regions. Providing flexible access services with an optical view toward the network's center, multiservice provisioning and switching network elements are landing on the customer-facing edges of today's new optical networks.

Figure 3-12 shows the typical positioning of the Cisco ONS 15454 MSPP and the ONS 15600 MSSP within the MAN architecture. The ONS 15454 MSPP is often deployed at the edge of metropolitan provider networks based on SONET/SDH rings. The MSPP provides customer-facing communication services and connects back to the service provider core via optical-based SONET/SDH rings or laterals. The ONS 15600 MSSP provides for broadband aggregation and switching of multiple MSPP rings aggregating into the core of provider networks. The MSSP often facilitates metropolitan connection to long-haul and extended long-haul (LH/ELH) networks.

Figure 12

Figure 3-12 MSPP and MSSP Metropolitan Application

The next sections describe both platforms in more detail.

Multiservice Provisioning Platform (MSPP)

The market for MSPPs emerged in 2000, starting the century strong with network edge technology turnover and service positioning. This market was seeded by technology pioneered by up-start Cerent, which was acquired by Cisco in 1999. One year later, the MSPP market gathered $1 billion in revenue on a worldwide basis.

The primary appeal for MSPPs is to consolidate long-established SONET/SDH ADMs in the multiservice metro, while incorporating Layer 2 and new Layer 3 IP capabilities with packet interfaces for Ethernet, Fast Ethernet, and Gigabit Ethernet opportunities. Many MSPPs contain additional support for multiservice interfaces and dense wavelength division multiplexing (DWDM) to optimize the use of high-value metropolitan optical fiber. Deployed as a springboard for the rapid provisioning of multiple services, the intrinsic value of these new-generation platforms is to build a bridge from circuit-based transport to packet-based services. MSPPs help providers to execute that strategy while maintaining established services with TDM switching support and SONET/SDH capabilities.

Entering the market near the end of many legacy SONET/SDH ADM depreciation schedules, the MSPPs inherit a sizable portion of their justification from reduced power, space, and maintenance requirements. In doing so, MSPPs help with continued optimization of operating budgets while representing strategic capital investments for new high-value service opportunity.

It is difficult to discuss SONET/SDH without a reference of the bandwidth speeds and terminology used by these worldwide standards. Table 3-4 shows a comparison of SONET/SDH transmission rates.

Table 3.4

Table 3-4 Comparison of SONET/SDH Transmission Rates

Many MSPP devices carry support for optical trunk rates from OC-3/STM-1 and OC-12/STM-4 to OC-48/STM-16 and OC-192/STM-64. This provides flexibility in using the MSPP for metropolitan edge access services (trunk rates of OC-3/STM-1 and OC-12/STM-4) and even for metropolitan core applications when MSPPs include support for OC-48/STM-16 and OC-192/STM-64 speed optical interfaces. A small percentage of MSPPs are used in long-haul applications, particularly when the platform includes reasonable numbers of optical interfaces at OC-48/STM-16 and OC-192/STM-64.

In the MSPP market, the primary Cisco offering is the ONS 15454 SONET/SDH-based MSPP, supporting DS1/E1 to OC-192/STM-64, TDM switching, switched 10/100/1000 line-rate Ethernet, DWDM, and other features in a compact chassis. Combining STS-1/VC-3/VC-4 and VT 1.5/VC-12 bandwidth management, packet switching, cell transport, and 3/1 and 3/3 transmux functionality, the ONS 15454 reduces the need for established digital cross-connect elements at the customer-facing central offices. The ONS 15454 MSPP supports TDM, ATM, video, IP, Layer 2, and Layer 3 capabilities across OC-3 to OC-192 unidirectional path-switch rings (UPSRs); two- or four-fiber bidirectional line switch rings (BLSRs); and linear, unprotected, and path-protected mesh network (PPMN) optical topologies.

Figure 3-13 shows the concept of service delivery on the ONS 15454 MSPP. This diagram shows a conceptual chassis layout of the Cisco ONS 15454 MSPP using the cross-connect timing control and SONET/SDH OC-48/STM-16 trunk cards. Also shown is an ML series Ethernet card for the provisioning of Gigabit Ethernet for Transparent LAN Services (TLS). The figure also depicts how these different services can be aggregated via STS bandwidth increments, effectively packing multiple services within the OC-48/STM-16 optical uplink.

With Ethernet connectivity services in high demand at the metro edge, the ONS 15454 MSPP delivers a very strong Ethernet portfolio. The ONS 15454 uses multiple series of data cards to support Ethernet, Fast Ethernet, and Gigabit Ethernet over SONET/SDH. These card types are the E series, G series, ML series, and CE series Ethernet data cards. Ethernet over SONET/SDH services can be combined within 15454 Ethernet cards via STS scaling in a variety of increments, depending on the type of Ethernet card used. Table 3-5 shows typical STS values and their respective aggregate line rate.

Table 3-5 STS Bandwidth Scaling

STS Bandwidth Increment

Effective Line Rate (Mbps)













Figure 13

Figure 3-13 Service Delivery on the Cisco ONS 15454 MSPP

Cisco ONS 15454 E Series Ethernet Data Card

The E series data cards support 2.4 Gbps of switching access to the TDM backplane, interfacing at STS rates up to STS-12. These cards support 10 Mbps Ethernet, 100 Mbps Fast Ethernet, and 1000 Mbps Gigabit Ethernet (limited to 622 Mbps) using STS bandwidth scaling at increments of STS-1c, STS-3c, STS-6c, and STS-12c. These cards are useful for setting up point-to-point Ethernet private lines, which don't need Spanning Tree Protocol (STP) support.

Cisco ONS 15454 G Series Ethernet Data Card

The G series data cards are higher-density Gigabit Ethernet cards, supporting access to the ONS 15454's TDM backplane at rates up to STS-48/VC-x-y. STS/VC bandwidth scaling is available for the real concatenation (RCAT) standard in selectable increments of STS-1, STS-3c, STS-12c, and STS-24c. The extended concatenation (ECAT) standard is supported with increments of STS-6c, STS-9c, and STS-24c. The G series cards yield higher performance with aggregate access rates of four times the E series cards. All Ethernet frames are simply mapped into SONET/SDH payloads, so there are fewer design constraints and ultra-low latency. The cards also support Gigabit Etherchannel or the 802.3 ad link aggregation standard, so that multigigabit Ethernet links can be created to scale capacity and link redundancy. The G series cards are targeted at the point-to-point Ethernet private line market, where speeds beyond 1 Gbps are desired services.

Cisco ONS 15454 ML Series Ethernet Data Card

With the ML series data cards, you can create any point-to-point or multipoint Ethernet service using the Layer 2 or Layer 3 control planes or via the software provisioning tools. These cards are used primarily for Fast Ethernet and Gigabit Ethernet support. Multiple levels of priority are available for class of service awareness, as is the ability to guarantee sustained and peak bandwidths.

These cards access the TDM backplane at an aggregate level of 2.4 Gbps. The ML series Ethernet ports can be software provisioned from 50 Mbps to the port's full line rate in STS-1, STS-3c, STS-6c, STS-9c, STS-12c, and STS-24c increments. Bandwidth guarantees can be established down to 1 Mbps.

ML series cards take advantage of features within Cisco IOS software, sharing a common code base with Cisco enterprise routers. The ML series includes two virtual Packet over SONET/SDH ports, which support Generic Framing Protocol (GFP) and virtual concatenation (VCAT) with software-based Link Capacity Adjustment Scheme (SW-LCAS). EoMPLS is supported as a Layer 2 bridging function. Virtual LANs (VLANs) can be created using the IEEE 802.1Q VLAN encapsulation standard, which can tag up to 4096 separate VLANs and additionally supports the IEEE 802.1Q tunneling standard (Q-in-Q) and Layer 2 protocol tunneling. Layer 2 Ethernet VPNs are best supported via the 802.1Q tunneling standard using this double-tagging hierarchy to preserve provider VLANs. It does this by tunneling all of the customer's 802.1Q tagged VLANs within a single provider 802.1Q VLAN instance. For Layer 2 VPN delivery across multiple SONET/SDH rings, a combination of IEEE 802.1Q tunneling in the access layer and EoMPLS across the core is a recommended design practice. All of these features allow for a strong Ethernet rate shaping functionality at the edge with highly reliable SONET/SDH protection.

Cisco ONS 15454 CE Series Ethernet Data Card

The CE series card is named for "Carrier Ethernet." This card is designed for optimum delivery of carrier-based, private-line Ethernet services, leveraging enhanced capabilities over SONET/SDH MSPP networks. Specifically, this card supports eight ports of 10/100BASE-T RJ45 Ethernet. What is key is that the CE series card supports Packet over SONET/SDH virtual interfaces, supports GFP, and can use high-order VCAT and LCAS for optimum bandwidth over SONET/SDH efficiency and in-service bandwidth capacity adjustments. Typical Ethernet features and 802.1p Type of Service (ToS) is supported.

The card has a maximum aggregate capacity of 600 Mbps, yielding a low oversubscription ratio if all eight ports are provisioned for full 100BASE-T operation. Each port can be configured from 1.5 Mbps to 100 Mbps, leveraging the capabilities of low-order and high-order VCAT. Each port forms a virtual concatenation group (VCG) using contiguous concatenation (CCAT) or VCAT, and port traffic from these eight Ethernet interfaces is mapped into the virtual Packet over SONET (PoS) interfaces via either GFP or High-Level Data Link Control (HDLC) framing. Each port forms a one-to-one relationship, as each port-based VCG is identifiable within the resulting SONET/SDH circuit that is created upstream of the ONS 15454 MSPP. Since each VCG is identifiable, LCAS can then be used to dynamically adjust individual port bandwidth capacity on-the-fly, in real time. A customer can order 1.5 Mbps Ethernet service and then grow to 100 Mbps capacity in appropriate increments on an in-service basis. This facilitiates a key differentiator for providers looking to craft dynamic provisioning of Ethernet-based services.

Multiservice Switching Platforms (MSSP)

The MSSP is a natural follow-on to the success of the MSPP. The MSSP is a new-generation SONET/SDH, metro-optimized switching platform that switches higher-bandwidth traffic from MSPP edge to edge or from edge to core, allowing metro networks to scale efficiently.

When you consider that edge MSPPs increase bandwidth aggregation from typical OC-3/STM-1 and OC-12/STM-4 bulk traffic to new levels of OC-48/STM-16 and OC-192/STM-64, the bandwidth bottleneck can move from the metropolitan edge to the metropolitan core. The increased bandwidth shifts the management focus from DS0s and T1s to SONET STS or SDH VC-4 levels. As this bandwidth is delivered toward the network core, efficient scaling is needed, particularly for large metropolitan areas. The MSSP serves that need by aggregating high-bandwidth MSPP edge rings onto the provider's interoffice ring. Its high-density design and small footprint positions the MSSP device to replace multiple, often stacked, high-density SONET ADMs and broadband digital cross-connects (BBDXCs) that are used to groom access rings to interoffice rings. This allows a reduction in network element platforms and single points of failure within central offices of the MAN architecture.

Figure 3-14 shows this concept of not only consolidating equipment and functionality within the central office but the added benefit of Layer 2 switching capability using the Cisco MSSP and MSPP architecture.

Figure 14

Figure 3-14 SONET/SDH Network Element Consolidation Using Cisco MSSP and MSPP

The MSSP is a true multiservice platform that leverages a provider's investment in SONET or SDH optical infrastructure. Supporting a wide variety of network topologies makes the MSSP adaptable to any optical architecture. In SONET networks, the Cisco MSSP supports UPSRs, as stated by Telcordia's GR-1400, and two-fiber and four-fiber BLSRs and 1+1 automatic protection switching (APS), as stated by Telcordia's GR-1230. In SDH networks, the Cisco MSSP supports subnetwork connection protection (SNCP) rings, multiplex section shared protection ring (MS-SPRing), and SDH multiplex section protection (MSP) topologies as defined by International Telecommunication Union (ITU) recommendations. Additionally, the Cisco MSSP supports the PPMN. A PPMN topology allows for optical spans to be upgraded incrementally to higher bandwidth as traffic requirements dictate, rather than upgrading a complete UPSR span all at once with traditional topology designs.

Leveraging the MSSP's integrated DWDM capability keeps the number of discrete network elements small. DWDM is a critical requirement in the MAN as new lambda-based services become necessary to address the number of discrete service requirements of customers, while also extending the capacity and life of a provider's metropolitan fiber plant.

The MSSP also incorporates MSPP functions, which is necessary to perform the following tasks:

  • Connect and switch TDM voice to Class 5 TDM voice switches
  • Switch ATM cells to ATM switches
  • Switch packets to IP routers

All of these devices are typically found in a provider's service point of presence (POP). By including support for Gigabit Ethernet in the MSSP, the platform can perform MSPP functions at this service POP level, reducing or eliminating the need for a discrete MSPP platform in that portion of the provider's network. This capability also strengthens integration between MSPP-to-MSSP-to-MSPP services, as MSPP edge traffic passes through the metro core, often destined for other edge MSPPs.

The lead Cisco product in the MSSP market is called the ONS 15600 MSSP. The ONS 15600 is optimized for metro MSPP aggregation deployments and typically displaces established SONET ADMs and BBDXCs at service POPs. It also competes well against many of the next-generation optical cross-connects that are more optimized for the long-haul core environment rather than the metro and also lack the SONET MSPP integration and long-reach optics capabilities required in the metro.

The heart of the ONS 15600 is a fully redundant 320 Gbps switch fabric with a three-stage pseudo-CLOS architecture in a 25x23.6x23.6 inch shelf. Line card slots are architected for 160 Gbps access to the switch fabric, and current line card densities use 25 percent of that capacity at up to 40 Gbps per line card with less than 25 millisecond protection switching. The use of the Any Service Any Port (ASAP) line card allows the ONS 15600 to be very flexible in supporting SONET/SDH optical interfaces of OC-3/STM-1, OC-12/STM-4, OC-48/STM-16, and Gigabit Ethernet, including the use of multirate small form-factor pluggable (SFP) optics that can be in-service software provisioned to change a selected port's optical interface from OC-3/STM-1 to OC-12/STM-4, OC-48/STM-16, or Gigabit Ethernet.

The 160 Gbps-per-slot architecture positions the ONS 15600 for upgrades to OC-768/STM-256 capabilities and integrates support beyond Gigabit Ethernet to 10 Gigabit Ethernet and DWDM interfaces.

The ONS 15600 uses industry-leading port densities per line card accommodating up to

  • 128 OC-3/STM-1s (using an ASAP line card)
  • 128 OC-12/STM-4s (using an ASAP line card
  • 128 OC-48/STM-16s (using an ASAP line card)
  • 32 OC-192/STM-64s
  • 128 Gigabit Ethernet (using an ASAP line card) per 15600, depending on the line card mixture

Three ONS 15600 shelves can be mounted in a standard seven-foot rack, a typical defacto measure of port and switching capacity, allowing for up to 960 Gbps of switching fabric with up to 384 OC-48/STM-16s, or up to 96 OC-192/STM-64s per rack. The ONS 15600 has a 20-year serviceability lifetime, extending the life of its components by derating their power consumption by 50 percent.

Figure 3-15 depicts the positioning of Cisco multiservice switching ATM and SONET/SDH platforms relative to optical capabilities and switching capacity shown earlier in Figure 3-4.

Figure 15

Figure 3-15 Cisco Multiservice Platforms

Figure 3-16 shows the typical positioning of Cisco multiservice platforms within the MAN architecture.

Figure 16

Figure 3-16 Cisco Multiservice Platform Positioning

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