Juniper IP Services - Quality of Service

IP Services - Quality of Service

Quality of service is becoming more and more important for several reasons, including:

• Bandwidth oversubscription of the edge and the need to prioritize traffic; for example, business subscribers can be prioritized over residential users and mission-critical applications over best-effort data
• Converged network infrastructure; that is, voice traffic is now carried over data networks
• Service providers want to offer differentiated traffic classes to gain new revenue streams

In most service provider networks, the IP edge is oversubscribed in terms of bandwidth. Oversubscription at the edge calls for mechanisms to provide contractually agreed upon bandwidth guarantees, as well as to make sure that subscribers get at least a fair amount of the bandwidth that is available.

Therefore, the following features must be supported in the edge router to ensure traffic prioritization and true QoS at the edge:

• S-CBQ (subscriber class-based queuing), which allows a set of different traffic classes per IP interface and subscriber
• Per subscriber and per IP interface queuing; that is, a queue per traffic class and subscriber to support
• Varied queuing algorithms such as HRR (hierarchical round robin) and SPQ (strict priority queuing) that can be attached to a physical port, subport level (for example, ATM PVC), and IP interface (subscriber)
• Wire-speed forwarding on all interfaces and all packet sizes. That is, the ability to perform route lookup and packet forwarding at line rate in all circumstances without dropping a single packet, even at packet sizes of 40 bytes
• Wire-speed classification of all packets on all interfaces: on the ingress and the egress interface. Packet classification is used to determine the traffic class to which an IP packet belongs and the service it gets. If a system cannot classify at wire speed, it must drop packets, even packets with the highest priority
• Wire-speed performance while applying policy decisions on forwarding, imposing rate limits, and reclassifying packets such as marking and stamping and queuing packets.

A high-aggregation edge router and B-RAS, such as the E-series system, must potentially support tens of thousands of queues for each line module, because each subscriber can have multiple queues.

Datasheets:

• Juniper networks E-series broadband services routers
• Juniper networks E320 and E120 broadband services routers
• Juniper networks JUNOSe

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