1. Cisco S4C6
Frame Relay

2. WAN Technologies PPP ISDN Frame Relay
CCITT standard that defines a process for sending data over a public data network
Connection Oriented
single path, reserved resources, sequential

3. Network Considerations
Carrier-provided public network or private network
Can be computers, servers, etc.
Can be switches, routers, CSU/DSU

4. Frame Relay Terms Access Rate – clock spped
DLCI – Data Link Connection Identifier – number that ids end point – significant only to local network – switch maps DLCIs between routers to form virtual circuit
LMI – signaling standard between CPE device and Frame Relay switch that manages connections and maintains status

5. Frame Relay Terms 2
CIR – Committed Information Rate – guaranteed rate in bits per second
Committed Burst – maximum number of bits switch agrees to transfer during a time interval
Excess burst – max number of uncommitted bits switch attempts to transfer beyond CIR
FECN - a bit that notifies DTE congestion avoidance procedures should be initiated; congestion has occurred
BECN – same but transmit rate will be reduced by 25%
DE –set bit that drops packets on priority number

6. Standards
No standards for connecting equipment inside Frame Relay network exist
Traditional circuit and packet switching can be used
Speeds can range from 56 kbps to 2 Mbps<

7. PVC Identification
DLCIs are assigned to represent a simplified addressing scheme
Users can share bandwidth at reduced cost
Permanent virtual circuits are administratively configures and managed in Frame Relay netowkr
Provides way to multiplex many logical data conversations
Complete path to destination is established before first frame is sent

8. Frame Relay Frame
Flag
Address (includes DLCI, FECN, BECN, and DE bits)
1024 DLCI addresses can be created
Cisco LMI supports
Data
FCS

9. Standardization Attempt
1990 –Cisco, StrataCom, Northern Telecom, and DEC
Extended Frame Relay protocol – extension is called LMI (Local Management Interface)
Determines operational status of PVCs
Transmits keepalice packets
Tells router what PVCs are available
Types are ansi, cisco, and q933a

10. Extensions
Virtual Circuit status (common) provides communication and synchornizationbetween network and user device
Multicasting (optional) single frame sent to multiple recipients
Global (optional) resembles LAN
Simple flow control (optional) Xon/Xoff

11. LMI Frame Format Flag LMI DLCI Unnumbered Information Indicator
Protocol Discriminator
Call Reference
Message Type
Information Element, FCS Flag

12. LMI Features Global addressing Multicasting Inverse ARP
Builds a frame relay map
Learns DLCIs in use and sends an Inverse ARP to each DLCI for each protocol
Router next hop resolved to Frame Relay DLCI

13. Frame Relay Switching Tables
Four Entries – two for incoming port and DLCI and two our outgoing port and DLCI
Port reference can change but DLCI does not change

14. Subinterface
Multiple logical interfaces can be cereated from one physical interface making Frame Relay more versatile and less costly
Each PVC is configured as point to pont connections which allows subinterface to act as a dedicated line
Allows single router interface to service many remote locations through individual unique subinterfaces

15. Split Horizon Available with Frame Relay No different in how it works
Connection types
Point to point
Multipoint

16. Frame Relay Configuration
Select Interface and go into configuration mode
Configure a network layer address
Select encapsulation type – cisco or IETF
Specify LMI type (11.1 or earlier) – ansi, cisco or q933a

17. Frame Relay Commands Show interfaces serial Show frame-relay pvc
Show frame-relay map
Show frame-relay lmi

18. Configuring the Serial Interface
Int s0
Encapsulation frame-relay
No shutdown

19. Configuring subinterfaces
Select interface
Remove network-layer addresses assigned to interface
Configure Frame Relay encapsulation
Select subinterface to configiure and identify as multipoint or point to point
Configure local DLCI for subinterface
frame-relay interface-dlci NUMBER