Chapter 10 Ethernet Operation

10.4.3 VLAN

The bridge sends bridge packets to the PPP half-bridge, which converts them to routed packets and forwards them to other router processes. Likewise, the PPP half-bridge converts routed packets to Ethernet bridge packets and sends them to the bridge on the same Ethernet subnetwork.

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

10.4.3 VLAN

The ASAP line card is transparent to VLAN tag information in the Ethernet frame.

Note VLANs are tunneled, and not terminated.

10.5 Buffering and Flow Control

Because the STS circuits can often be oversubscribed (have a bandwidth lower than that needed to support the traffic on the Ethernet port), a combination of buffering and local flow control is supported. Initially, frames that arrive on an ingress interface that cannot be transmitted immediately on the egress interface are placed in an ingress buffer. When this buffer starts filling up and is in danger of overflowing, flow control is employed. Local flow control is flow control between the Ethernet interface and the router or switch it is connected to, over the single Ethernet link. This is depicted in Figure 10-3.

Figure 10-3 Buffering and Flow Control

Ethernet links

Router

 

15xxx

15xxx

 

 

 

 

 

SONET network

 

 

 

Flow Control

Flow Control

 

 

 

- PAUSE

 

- PAUSE

 

frames

 

frames

Router

124485

To prevent dropping of frames on an ingress Ethernet interface due to buffer congestion, an Ethernet interface sends a PAUSE frame to its peer on its egress Ethernet interface. An Ethernet interface might be capable of both sending and receiving PAUSE frames (symmetric flow control). On the other hand, it might be capable of performing only one of the two (asymmetric flow control). Two factors determine what an Ethernet interface ultimately ends up supporting:

•Flow control capability of the interface as provisioned by the operator (fixed at OFF or ON)

•Flow control capability of the peer as determined by AutoNegotiation

The Ethernet interfaces are capable of using symmetric or asymmetric flow control to meter packet receptions according to the requirements specified in IEEE 802.3x. This is done to avoid dropping packets internally due to output or input queue congestion. When an Ethernet interface uses symmetric

Cisco ONS 15600 Reference Manual, R7.2

10-6

Page 221 Page 223
Page 222
Image 222
Cisco Systems ONS 15600 manual Buffering and Flow Control, Vlan, 10-6
Page 221 Page 223

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.
Top Page Image Contents