Frame Relay
Frame Relay is a packet-switching telecommunications service designed for cost-efficient data transmission for intermittent traffic between local area networks (LANs) and between endpoints in wide area networks (WANs).
It is NBMA - no native b-cast support (can be enabled and emulate)
Split Horizont issue for RIP and EIGRP.
Frame relay puts data in a variable-size unit called a frame.
For most services, the network provides a permanent virtual circuit (PVC). That means the customer sees a continuous, dedicated connection without paying for a full-time leased line.
By contrast, switched virtual circuits (SVC) are temporary connections that are destroyed after a specific data transfer is completed.
Local Management Interface LMI
- It’s a keepalive mechanism.
- It tells us if the PVC is active or inactive.
- It also gives us a DLCI (Data Link Connection Identifier).
Types of LMI:
- Cisco
- ANSI T1.617 Annex D
- ITU-T Q.933 Annex A
Data Link Connection Identifier DLCI
- FR doesn’t use MAC addresses since that’s Ethernet but we uses DLCI instead.
- For each PVC we get a DLCI per router.
FrameRelay packet example:
Frame 1: 104 bytes on wire (832 bits), 104 bytes captured (832 bits)
Frame Relay
First address octet: 0x18
Second address octet: 0x61, EA
DLCI: 102
Type: IP (0x0800)
Internet Protocol Version 4, Src: 10.0.0.1, Dst: 10.0.0.2
Internet Control Message Protocol
FRSwitch config:
hostname FRSwitch
!
frame-relay switching
!
interface Serial1/1
description R1
no ip address
encapsulation frame-relay
clock rate 128000
frame-relay intf-type dce
frame-relay route 102 interface Serial1/2 201
frame-relay route 103 interface Serial1/3 301
!
interface Serial1/2
description R2
no ip address
encapsulation frame-relay
clock rate 128000
frame-relay intf-type dce
frame-relay route 201 interface Serial1/1 102
!
interface Serial1/3
no ip address
encapsulation frame-relay
clock rate 128000
frame-relay intf-type dce
frame-relay route 301 interface Serial1/1 103
!
Router 1/2/3:
interface Serial0/1/0
no ip address
encapsulation frame-relay
Show outputs:
FRSwitch:
FRSwitch#show frame-relay route
Input Intf Input Dlci Output Intf Output Dlci Status
Serial1/1 102 Serial1/2 201 active
Serial1/2 201 Serial1/1 102 active
Router:
R1#show frame-relay pvc
PVC Statistics for interface Serial0/0/0 (Frame Relay DTE)
Active Inactive Deleted Static
Local 0 0 0 0
Switched 0 0 0 0
Unused 1 0 0 0
DLCI = 102, DLCI USAGE = UNUSED, PVC STATUS = ACTIVE, INTERFACE = Serial0/0/0
input pkts 0 output pkts 0 in bytes 0
out bytes 0 dropped pkts 0 in pkts dropped 0
out pkts dropped 0 out bytes dropped 0
in FECN pkts 0 in BECN pkts 0 out FECN pkts 0
out BECN pkts 0 in DE pkts 0 out DE pkts 0
out bcast pkts 0 out bcast bytes 0
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
pvc create time 00:00:25, last time pvc status changed 00:00:25