Cisco CISCO1751 Quick Start Manual page 27

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:
•
•
•
If you configure multilink PPP interleaving, you can use the ip rtp reserve command instead of
Note
configuring RSVP. Refer to the next section on
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-qos dial-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-qos controlled-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:
•
•
Do not use multilink PPP on links faster than 2 Mbps.
Note
78-11259-05
Links slower than 2 Mbps
Links with high utilization
Need for the best possible voice quality
Point-to-point connections using PPP encapsulation
Links slower than 2 Mbps
"Multilink PPP Interleaving."
Cisco 1751 Voice-over-IP Quick Start Guide
Configuring Voice-over-IP
27