Chapter 10 Ethernet Operation

10.3.4 Oversubscription

Note Mapping depends on the particular concatenation being supported on the card. It also depends on the concatenation being supported on all of the network elements (NEs) that the end-to-end circuit is being built through.

For full line-rate mapping to ensure that no frames are dropped, a GE interface is mapped to either an STS-24c or an STS-48c. At the STS-24c rate, the effects of bandwidth expansion due to HDLC/GFP/ITU X.86 encapsulations need to be taken into account to ensure no packet loss.

10.3.4 Oversubscription

Oversubscription of data interfaces is the mapping of an interface to a path with a lower bandwidth than the rate of the interface. When oversubscribing, the operator is relying on the fact that on data interfaces, packet transmission rates and utilization is not always 100 percent. For example, a customer with a GE interface might transmit at an average rate of only 100 Mbps.

To ensure that packet loss does not occur or that any ensuing packet loss is minimized, system engineers need to carefully estimate the amount of memory in the NE that is required to sustain any traffic bursts. Traffic bursts are characterized by several different models that take into account such parameters as the mean rate, peak rates, length of burst, and so on. Performing these calculations is more important in switching applications than in transport applications.

In the ONS 15600, oversubscription of interfaces is supported. This occurs when the GE interface is mapped to any of the STS-1, STS-3, STS-6, STS-9, and STS-12 (c) rates. No guarantees on frame loss or delay due to oversubscription is provided by the system. Actual loss and delay values depend on incoming Ethernet traffic patterns.

10.4 Protocols over Ethernet

The ASAP card supports the BCP, PPP Half Bridge, and VLAN protocols, described in the following subsections.

10.4.1 Bridge Control Protocol

Support of BCP is relevant between two routers or bridges. An Ethernet card providing transport functionality is neither a router nor a bridge. Therefore, even BCP encapsulation is not supported on the Ethernet ports of the ASAP transport line card.

The ASAP line card Ethernet function is transparent to any Layer 2 and above protocol packets (the entire control plane). Any BCP control packets are transported out to the SONET interface.

10.4.2 PPP Half Bridge

For situations in which a routed network needs connectivity to a remote bridged Ethernet network, a serial or integrated services digital network (ISDN) interface can be configured to function as a PPP half-bridge. The line to the remote bridge functions as a virtual Ethernet interface, and the router's serial or ISDN interface functions as a node on the same Ethernet subnetwork as the remote network.

Cisco ONS 15600 Reference Manual, R7.2

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ONS 15600 specifications

Cisco Systems ONS 15600 is a highly versatile optical networking platform designed to meet the demands of modern telecommunications and data services. This multiservice edge platform supports various transmission mediums and offers a wide array of features that enable efficient data transport. Ideal for service providers and large enterprises, the ONS 15600 is engineered to provide scalable and reliable optical transport solutions.

One of the notable features of the ONS 15600 is its capability to support multiple protocols, including SONET/SDH, Ethernet, OTN, and legacy TDM services. This flexibility allows users to tailor their networks according to specific service requirements while ensuring interoperability with existing infrastructure. The platform is designed to facilitate seamless service migration, accommodating both legacy and next-generation services.

The modular architecture of the ONS 15600 enhances its scalability. It allows for easy expansion by incorporating additional line cards or interface modules without requiring significant downtime. This modularity ensures that service providers can evolve their networks over time, responding to increasing bandwidth demands and new service offerings with ease.

Incorporating advanced technologies, the ONS 15600 employs Dense Wavelength Division Multiplexing (DWDM), significantly increasing the capacity of fiber networks by allowing multiple signals to be transmitted simultaneously over a single optical fiber. This capability helps to optimize fiber utilization and reduce operational costs. In addition, the platform supports Optical Transport Network (OTN) for improved error detection and correction, contributing to higher reliability and performance.

Another key characteristic of the ONS 15600 is its robust management capabilities. The platform can be managed through Cisco's Optical Networking Manager (ONM), providing a centralized interface for network configuration, monitoring, and troubleshooting. This enhances operational efficiency and minimizes downtime, allowing service providers to focus on delivering quality services to their customers.

The ONS 15600 also prioritizes security, offering various features like encryption and access control to safeguard sensitive data during transmission. With its combination of scalability, flexibility, and security, the Cisco ONS 15600 stands out as a reliable choice for organizations looking to enhance their optical networking capabilities while meeting the evolving demands of the digital landscape. Its commitment to quality and performance makes it a cornerstone of modern optical networks.
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