© 2006 Cisco Systems, Inc. All rights reserved.ONT v Introduction to IP QoS Identifying Models for Implementing QoS

© 2006 Cisco Systems, Inc. All rights reserved.ONT v QoS Models

© 2006 Cisco Systems, Inc. All rights reserved.ONT v QoS Models ModelCharacteristics Best effortNo QoS is applied to packets. IntServApplications signal to the network that they require certain QoS parameters. DiffServThe network recognizes classes that require QoS.

© 2006 Cisco Systems, Inc. All rights reserved.ONT v Best Effort Model

© 2006 Cisco Systems, Inc. All rights reserved.ONT v Best-Effort Model Internet was initially based on a best-effort packet delivery service. Best-effort is the default mode for all traffic. There is no differentiation among types of traffic. Best-effort model is similar to using standard mailIt will get there when it gets there.

© 2006 Cisco Systems, Inc. All rights reserved.ONT v Benefits and Drawbacks of the Best-Effort Model Benefits: –Highly scalable –No special mechanisms required Drawbacks: –No service guarantees –No service differentiation

© 2006 Cisco Systems, Inc. All rights reserved.ONT v IntServ Model

© 2006 Cisco Systems, Inc. All rights reserved.ONT v IntServ Model Introduction of IntServ model (RFC 1633) was driven by real-time applications, such as remote video and conferencing. IntServ end-to-end model ensures guaranteed delivery and predictable behavior of the network for applications. Resource Reservation Protocol (RSVP) is used as a signaling protocol. The requested QoS parameters are then linked to a packet stream. End-to-end streams are not established if the required QoS parameters are not available.

© 2006 Cisco Systems, Inc. All rights reserved.ONT v IntServ Model (Cont.) Provides multiple service levels Requests specific kind of service from the network before sending data Uses RSVP to reserve resources for specified QoS parameters Intelligent queuing mechanisms required to provide resource reservation in terms of: –Guaranteed rate –Controlled load (low delay, high throughput)

© 2006 Cisco Systems, Inc. All rights reserved.ONT v IntServ Functions IntServ requires several functions on routers and switches along the path: Admission control Classification Policing Queuing Scheduling

© 2006 Cisco Systems, Inc. All rights reserved.ONT v Benefits and Drawbacks of the IntServ Model Benefits: –Explicit resource admission control (end to end) –Per-request policy admission control (authorization object, policy object) –Signaling of dynamic port numbers (for example, H.323) Drawbacks: –Continuous signaling because of stateful architecture –Flow-based approach not scalable to large implementations, such as the public Internet (can be made more scalable when combined with elements of the DiffServ model)

© 2006 Cisco Systems, Inc. All rights reserved.ONT v RSVP and the IntServ QoS Model

© 2006 Cisco Systems, Inc. All rights reserved.ONT v Resource Reservation Protocol Is carried in IPprotocol ID 46 Can use both TCP and UDP port 3455 Is a signaling protocol and works in conjunction with existing routing protocols Requests QoS parameters from all devices that are between the source and the destination Is intended to provide divergent performance requirements for multimedia applications: –Rate-sensitive traffic –Delay-sensitive traffic

© 2006 Cisco Systems, Inc. All rights reserved.ONT v RSVP Operation

© 2006 Cisco Systems, Inc. All rights reserved.ONT v RSVP in Action RSVP sets up a path through the network with the requested QoS. RSVP is used for CAC in Cisco Unified CallManager 5.0.

© 2006 Cisco Systems, Inc. All rights reserved.ONT v DiffServ Model

© 2006 Cisco Systems, Inc. All rights reserved.ONT v DiffServ Model DiffServ (RFC 2474 and RFC 2475) was designed to overcome the limitations of both the best-effort and IntServ models. Network traffic is identified by classes. Network QoS policy enforces differentiated treatment of traffic classes. You choose level of service for each traffic class.

© 2006 Cisco Systems, Inc. All rights reserved.ONT v Benefits and Drawbacks of the DiffServ Model Benefits: –Highly scalable –Many levels of quality possible Drawbacks: –No absolute service guarantee –Complex mechanisms

© 2006 Cisco Systems, Inc. All rights reserved.ONT v Summary There are three models for providing QoS: best effort, IntServ, and DiffServ. Although the best-effort model is highly scalable, it has no provision for differentiating among types of network traffic and, as a result, does not provide QoS. The IntServ model offers absolute QoS guarantees by explicitly reserving bandwidth by using RSVP. Scalability is achieved in conjunction with elements of the DiffServ model. RSVP is not a routing protocol; thus, implementing RSVP in an existing network does not require migration to a new routing protocol. The DiffServ model provides the ability to classify network traffic and offer many levels of QoS while being highly scalable.

© 2006 Cisco Systems, Inc. All rights reserved.ONT v