Cisco IOS Wide-Area Networking Configuration Guide - Free Books

Configuring Frame RelayCustomizing Frame Relay for Your NetworkIf the lowest link speed in the path is 64 kb/s, the recommended fragment size (for 10 ms serializationdelay) is 80 bytes. If the lowest link speed is 128 kb/s, the recommended fragment size is 160 bytes.For more information, refer to the “Fragmentation (FRF.12)” section in the VoIP over Frame Relay withQuality of Service (Fragmentation, Traffic Shaping, LLQ / IP RTP Priority) document.Verifying the Configuration of End-to-End FRF.12 FragmentationTo verify FRF.12 fragmentation, use one or more of the following EXEC commands:CommandRouter# show frame-relay fragment [interface interface][dlci]Router# show frame-relay pvc [interface interface] [dlci]PurposeDisplays Frame Relay fragmentation information.Displays statistics about PVCs for Frame Relayinterfaces.Frame Relay Fragmentation Using FRF.11 Annex CCisco-Proprietary FragmentationWhen VoFR (FRF.11) and fragmentation are both configured on a PVC, the Frame Relay fragments aresent in the FRF.11 Annex C format. This fragmentation is used when FRF.11 voice traffic is sent on thePVC, and it uses the FRF.11 Annex C format for data.With FRF.11, all data packets contain fragmentation headers, regardless of size. This form offragmentation is not recommended for use with Voice over IP (VoIP).See the chapter “Configuring Voice over Frame Relay” in the Cisco IOS Voice, Video, and FaxConfiguration Guide for configuration tasks and examples for Frame Relay fragmentation using FRF.11Annex C.Cisco-proprietary fragmentation is used on data packets on a PVC that is also used for voice traffic.When the vofr cisco command is configured on a DLCI and fragmentation is enabled on a map class,the Cisco 2600 series, 3600 series, and 7200 series routers can interoperate as tandem nodes (but cannotperform call termination) with Cisco MC3810 concentrators running Cisco IOS releases prior to12.0(3)XG or 12.0(4)T.To configure Cisco-proprietary voice encapsulation, use the vofr cisco command. You must thenconfigure a map class to enable voice traffic on the PVCs.See the chapter “Configuring Voice over Frame Relay” in the Cisco IOS Voice, Video, and FaxConfiguration Guide for configuration tasks and examples for Cisco-proprietary fragmentation.Frame Relay Fragmentation and Hardware Compression InteroperabilityFRF.12, FRF.11 Annex C, and Cisco-proprietary fragmentation can be used with FRF.9 or data-streamhardware compression on interfaces and virtual circuits (VCs) using Cisco-proprietary or InternetEngineering Task Force (IETF) encapsulation types.When payload compression and Frame Relay fragmentation are used at the same time, payloadcompression is always performed before fragmentation.Frame Relay fragmentation can be used with the following hardware compression modules:• Cisco 2600 AIM-COMPR241