Content

| 8.2 |  | Quality of Service Mechanisms |
| 8.2.3 |  | Integrated services model |

The Integrated Services or IntServ architecture is a multiple service model that can accommodate multiple QoS requirements. In this model the application requests a specific kind of service from the network before it sends data. The request is made by explicit signaling. The application informs the network of its traffic profile and requests a particular kind of service that can encompass its bandwidth and delay requirements. The application is expected to send data only after it gets a confirmation from the network. It is also expected to send data that lies within its described traffic profile.

The network performs admission control, based on information from the application and available network resources. It also commits to meeting the QoS requirements of the application as long as the traffic remains within the profile specifications. The network fulfils its commitment by maintaining a per-flow state and then performing packet classification, policing, and intelligent queuing based on that state.

The Cisco IOS IntServ model allows applications to make use of the IETF Resource Reservation Protocol (RSVP), which can be used by applications to signal their QoS requirements to the router.

Routers, in conjunction with RSVP, are able to use intelligent queuing mechanisms to provide two types of services:

- Guaranteed Rate Service – Which allows applications to reserve bandwidth to meet their requirements. Adaptive real-time applications, such as playback of a recorded conference, can use this kind of service.
- Controlled Load Service – Which allows applications to have low delay and high throughput even during times of congestion. For example, adaptive real-time applications such as playback of a recorded conference can use this kind of service. Cisco IOS QoS uses RSVP with Weighted Random Early Detection (WRED) to provide this kind of service.