Frame+Relay

=Frame Relay= toc


 * ===__Data Link Connection Identifiers (DLCI)__===
 * frame relay switches forward frame based on DLCI to a Virtual Circuit (VC)
 * locally significant
 * frame relay switches replace DLCI with the source DLCI before it forwards
 * ===__Local Management Interface (LMI)__===
 * between router and frame relay switch
 * Status Inquiry from DTE to switch
 * switch replies with Status Message that contains DLCIs and VCs
 * every 6th carries Full Status Message which contains more complete information about VCs
 * ====__**Keepalives**__====
 * LMI Status Enquiry (router) and Status (switch) function as keepalives
 * interface fails after (default 3) keepalive intervals (default 10 seconds)
 * config-if# [no] keepalive
 * ====__**Types**__====
 * **Cisco** - DLCI 16-1007 (992); LMI DCLI is 1023
 * **ANSI** - DLCI 16-991 (976)
 * **ITU (q933a)** - DLCI 16-991 (976)
 * config-if# frame-relay lmi-type [cisco | ansi | q933a]
 * ===__Headers & Encapsulation__===
 * uses different consecutive headers
 * ====__**First Header**__====
 * ITU Link Access Procedure for Frame-Mode Bearer Services (LAPF)
 * includes
 * DLCI
 * DE
 * BECN
 * FECN
 * fields used by FR to deliver frames across cloud
 * ===**__Second Header__**===
 * important only to DTEs on end of VC
 * two options
 * Cisco proprietary header (default)
 * IETF defined RFC 2427 header
 * Network Layer Protocol ID (NLPID)
 * config-if# encapsulation frame-relay ieft
 * config-if# frame-relay interface-dlci <#> ieft
 * config-if# frame-relay map dlci ... ieft
 * ===__Congestion__===
 * caused by speed mismatches
 * ====**__Adaptive Shaping__**====
 * uses FECN & BECN to inform router that VC is experiencing congestion
 * when a switch notices congestion cause by VC, sets FECN
 * when a switch sets a FECN, it tracks congested VC, next frame in opposite direction marked with BECN
 * FECN can be set by frame relay switches, but not routers
 * BECN can be set by routers and switches
 * routers can watch for FECN
 * config-pmap-c# shape fecn-adapt (CB)
 * config-if# traffic-shape fecn-adapt (FRTS)
 * ====**__Discard Eligibility Bit__**====
 * when queues fill and frames must be dropped, switches can examine DE to decide
 * ===__Configuration__===
 * ====__**Basics**__====
 * any DLCI learned with LMI that isn't associated with a subinterface will be used by physical interface
 * __**Payload Compression**__
 * three options
 * packet-by-packet
 * data stream
 * Frame Relay Forum Implementation Agreement 9 (FRF.9; standardized)
 * data stream compression (non proprietary)
 * uses LZS compression
 * dictionary - table of short codes and longer associated strings
 * packet-by-packet clears the dictionary after each packet
 * configured per VC
 * config-if# frame-relay payload-compress [frf9 | data-stream | ???] stac
 * config-if# frame-relay map ip ... 101 broadcast payload-compress [frf9 | data-stream | ???] stac
 * ====__**Fragmentation**__====
 * LFI over PVC defined in FRF.12
 * dual FIFO queues
 * high queue - FRTS LLQ packets
 * normal queue - from other queuing
 * recommended choosing fragment size so packets in LLQ PQ will not be fragmented
 * config-if# frame-relay fragment [end-to-end] (interface)
 * config-if-dlci-c# frame-relay fragment [end-to-end] (legacy; FRTS class)
 * ====__**LFI Using Multilink PPP (MLP)**__====
 * only option for Frame Relay-to-ATM Service Internetworking
 * LMP over frame relay uses PPP headers
 * =====**__Requires__**=====
 * QoS map policy that uses PQ with interleaving packets from this special queue
 * requires multilink interface
 * ip address
 * service-policy command
 * =====**__Configure__**=====
 * config-cmap# match dscp ef
 * config-pmap-c# priority percent 10
 * config# interface multilink1
 * config-if# bandwidth 256
 * config-if# ip address ...
 * config-if# ppp multilink
 * config-if# ppp multilink interleave
 * config-if# ppp multilink group 1
 * config-if# ppp multilink fragment delay 10
 * config-if# service-policy output WORD
 * config# interface virtual-template1
 * config-if# no ip address
 * config-if# ppp multilink
 * config-if# ppp multilink group 1
 * config# interface serial0/2
 * config-if# no ip address
 * config-if# encapsulation frame-relay
 * config-if# no fair-queue
 * config-if# frame-relay traffic-shaping
 * config-if# frame-relay interface-dlci 111 ppp virtual-template1

=Terms=

Permanent Virtual Circuit (PVC) Data Link Connection Identifier (DLCI) Local Management Interface (LMI) Network-to-Network Interface (NNI) Local Access Route/Committed Information Rate (CIR)

=Base Configuration=

config# interface s0/0 config-if# encapsulation frame-relay

=Sub-Interface Configuration=

config# no frame-relay inverse-arp (don't ask) config# no arp frame-relay (don't tell) config# interface s0/0.1 point-to-point (configure sub interface) config-subif# frame-relay interface-dlci 201 (point to point dlci mapping) conf-fr-dlci# config# interface s0/1.1 multipoint (configure sub interface) config-subif# frame-relay map ip 192.168.1.1 102 broadcast (multipoint dlci mapping) config-subif# no ip split-horizon eigrp 1 (disable split horizon for eigrp)

=View/Debug Commands=

show frame-relay lmi show frame-relay map show frame-relay pvc

=Traffic Shaping=

Terms
Tc - Timing Interval (1/8 Sec) Bc - Committed Burst Be - Excess Burst DE - Discard Eligible BECN - Backwards Explicit Congestion Notification FECN - Forwards Explicit Congestion notification



Basic Configuration
config# map-class frame-relay SLOW config-map-class# frame-relay adaptive-shaping becn (listen tot he BECNs) config-map-class# frame-relay mincir 24400 (BECN wont make it go any slower then this) config-map-class# frame-relay bc 3600 (288000/8) config-map-class# frame-relay be 200 (burst) config-map-class# frame-relay cir 28800 config-map-class# frame-relay tc 125 (1/8 sec in milli) config-map-class# traffic-rate 28800 30000 (sets cir and be) config# interface s0/0.1 config-subif# frame-relay class SLOW (applies to all DLCIs) config# interface s0/1.1 config-subif# frame-relay interface-dlci 102 config-fr-dlci# class slow (applies to specific DLCI)

show traffic-shape show compress