Cisco Systems 1760 Multilink PPP with Link Fragmentation Interleave, Real-Time Transport Protocol Header Compression

Multilink PPP with Link Fragmentation Interleave

Multilink PPP with link fragmentation interleave (MLPPP with LFI) allows large packets to be multilink-encapsulated and

fragmented into smaller packets, thus ensuring 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 MLPPP with LFI if you have a dialer, an 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 MLPPP with LFI on links faster than 2 Mbps.

To configure MLPPP with LFI on a dialer, ISDN PRI or ISDN BRI interface, or a virtual template, you must first configure

MLPPP with LFI on the interface or template by entering the following commands while in interface configuration mode:

Router(config-if)# encapsulation ppp

Router(config-if)# ppp multilink

Router(config-if)# ppp multilink interleave

Optionally, configure a maximum fragment delay:

Router(config-if)# ppp multilink fragment-delay milliseconds

You can also reserve a special queue for real-time packet flows to specified destination User Datagram Protocol (UDP) ports,

allowing real-time traffic to have higher priority than other flows. You need the following command only if you have not

configured RSVP:

Router(config-if)# ip rtp reserve lowest-UDP-port range-of-ports

For virtual templates only, apply the virtual template to the multilink bundle:

Router(config-if)# multilink virtual-template 1

To create a virtual template interface, enter the following interface virtual-template global configuration command:

Router(config)# interface virtual-template 1

Real-Time Transport Protocol Header Compression

Real-Time Transport Protocol (RTP) header compression on a PPP, HDLC, or similar serial interface compresses the packet

header to reduce network overhead.

You should configure RTP header compression on a serial interface if you have either of the following:

•Links slower than 2 Mbps

•A need to conserve bandwidth

Note Do not use RTP header compression on links faster than 2 Mbps.

Enable RTP header compression at both ends of the serial link by entering the ip rtp header-compression interface configuration

command:

Router(config-if)# ip rtp header-compression