Cisco Systems CISCO1751 quick start Rsvp, Multilink PPP Interleaving, Configuring RSVP

Configuring Voice-over-IP

RSVP

Resource Reservation Protocol (RSVP) enables routers to reserve enough bandwidth on an interface for reliable and quality performance. RSVP works well on PPP, HDLC, and similar serial line interfaces. It does not work well on multi-access LANs.

You should configure RSVP if you have a serial interface and any of the following:

•Links slower than 2 Mbps

•Links with high utilization

•Need for the best possible voice quality

Note If you configure multilink PPP interleaving, you can use the ip rtp reserve command instead of configuring RSVP. Refer to the next section on “Multilink PPP Interleaving.”

Configuring RSVP

By default, RSVP is disabled so that it is backwards compatible with routers that do not implement it. To enable RSVP on an IP network, enter the ip rsvp bandwidth command from interface configuration mode. The following example enables RSVP on serial interface 0/0 and sets the maximum bandwidth to

96 kbps and the maximum bandwidth per single request to 24 kbps:

Router(config)# interface serial 0/0

Router(config-if)#ip rsvp bandwidth 96 24

The default maximum bandwidth is 75 percent of the bandwidth available on each interface.

RSVP must be enabled at each LAN or WAN interface that voice packets will travel across. After enabling RSVP you must also use the req-qosdial-peer configuration command to request an RSVP session on each VoIP dial peer. Otherwise, no bandwidth is reserved for voice traffic.

Router(config-dial-peer)# req-qoscontrolled-load

For further information about this command, refer to the Cisco 1751 Router Software Configuration Guide.

Multilink PPP Interleaving

Multilink PPP interleaving allows large packets to be multilink-encapsulated and fragmented into smaller packets to make sure that voice packets are transmitted without delay; small real-time packets, which are not multilink-encapsulated, are transmitted between fragments of the large packets. The interleaving feature also provides a special transmit queue for the smaller, delay-sensitive packets, enabling them to be transmitted earlier than other flows.

You should configure multilink PPP interleaving if you have a dialer, ISDN PRI or BRI interface, or a virtual template, and either of the following:

•Point-to-point connections using PPP encapsulation

•Links slower than 2 Mbps

Note Do not use multilink PPP on links faster than 2 Mbps.

Cisco 1751 Voice-over-IP Quick Start Guide

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