RECURSO DE CASACIÓN - CÓDIGO ORGÁNICO GENERAL DE PROCESOS

• Provides multiple service levels

• Requests specific kind of service from the network before sending data

• Uses RSVP to reserve network resources

• Uses intelligent queuing mechanisms

• End to end

IntServ is a multiple-service model that can accommodate multiple QoS requirements. IntServ inherits the connection-oriented approach from telephony network design. Every individual communication must explicitly specify its traffic descriptor and requested resources to the network. The edge router performs admission control to ensure that available resources are sufficient in the network. The IntServ standard assumes that routers along a path set and maintain the state for each individual communication.

The role of Resource Reservation Protocol (RSVP) in the Cisco QoS architecture is to provide resource admission control for VoIP networks. If resources are available, RSVP accepts a reservation and installs a traffic classifier in the QoS forwarding path. The traffic classifier tells the QoS forwarding path how to classify packets from a particular flow and what forwarding treatment to provide.

In the IntServ model, the application requests a specific kind of service from the network before sending data. 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. The application 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. The network commits to meeting the QoS requirements of the application as long as the traffic remains within the profile specifications. The network fulfills

RSVP can be used by applications to signal their QoS requirements to the router.

Intelligent queuing mechanisms can be used with RSVP to provide these QoS service

levels:

— Guaranteed-rate: Guaranteed-rate service level allows applications to reserve bandwidth to meet their requirements. For example, a VoIP application can reserve 32 Mbps end to end using this type of service. Cisco IOS QoS uses low-latency queuing (LLQ) with RSVP to provide guaranteed-rate type of service.

— Controlled-load: Controlled-load service level allows applications to have low delay and high throughput, even during times of congestion. For example, adaptive real- time applications, such as the playback of a recorded conference, can use this service. Cisco IOS QoS uses RSVP with weighted random early detection (WRED) to provide controlled-load type of service.

IntServ Model (Cont.)

• RSVP QoS services

– Guaranteed-rate service

– Controlled-load service

• RSVP provides policy to QoS mechanisms

RSVP is an IP service that allows end systems or hosts on either side of a router network to establish a reserved-bandwidth path between them to predetermine and ensure QoS for their data transmission. RSVP is currently the only standard signaling protocol designed to guarantee network bandwidth from end to end for IP networks.

RSVP is an Internet Engineering Task Force (IETF) standard (RFC 2205) protocol for allowing an application to dynamically reserve network bandwidth. RSVP enables applications to

request a specific QoS for a data flow (shown in the graphic). Cisco implementation also allows RSVP to be initiated within the network, using configured proxy RSVP. Network managers can take advantage of RSVP benefits in the network, even for non-RSVP-enabled applications and hosts.

Hosts and routers use RSVP to deliver QoS requests to the routers along the paths of the data stream. Hosts and routers also use RSVP to maintain the router and host state to provide the requested service, usually bandwidth and latency. RSVP uses a mean data rate; that is, the largest amount of data the router will keep in queue and the minimum QoS used to determine bandwidth reservation.

LLQ or WRED act as the workhorses for RSVP, setting up the packet classification and scheduling that is required for the reserved flows. Using LLQ, RSVP can deliver an IntServ- guaranteed service. Using WRED, RSVP can deliver a controlled-load service. RSVP can be deployed in existing networks with a software upgrade.

IntServ Model (Cont.)

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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)

The main benefits of IntServ and RSVP are as follows:

RSVP signals QoS requests per individual flow. The network can then provide guarantees to these individual flows. The problem with this is that IntServ does not scale to large networks because of the large number of concurrent RSVP flows.

RSVP informs network devices of flow parameters (IP addresses and port numbers). Some

applications use dynamic port numbers, which can be difficult for network devices to recognize. Network-based application recognition (NBAR) is a mechanism that has been introduced to supplement RSVP for applications that use dynamic port numbers but do not use RSVP.

IntServ supports admission control, which allows a network to reject (or downgrade) new RSVP sessions if one of the interfaces in the path has reached the limit (that is, all

reservable bandwidth is booked).

The main drawbacks of IntServ and RSVP are as follows:

There is continuous signaling because of the stateful RSVP operation.

RSVP is not scalable to large networks where per-flow guarantees would have to be made

to thousands of concurrent RSVP flows.

In document CÓDIGO ORGÁNICO GENERAL DE PROCESOS (página 78-81)