- FRAME RELAY SIMPLEDIAGRAMS FULL
- FRAME RELAY SIMPLEDIAGRAMS VERIFICATION
- FRAME RELAY SIMPLEDIAGRAMS CODE
Forward-Explicit Congestion Notification (FECN) - A single-bit field that can be set to a value of 1 by a switch to indicate to an end DTE device (router) that congestion was encountered in the direction of the frame transmission from source to destination.These are the FECN, BECN, and DE bits they are the last 3 bits in the Address field. Congestion Control - Consists of the 3 bits that control the Frame Relay congestion-notification mechanism.C/R - The C/R (Command/Response) bit that follows is the most significant DLCI byte in the Address field.MPLS labels use the extended address field of the Frame Relay frame header. The eighth bit of each byte of the Address field is used to indicate the EA. Although current Frame Relay implementations all use a two-byte DLCI, this capability does allow for the use of longer DLCIs in the future. If the value is 1, then the current byte is determined to be the last DLCI byte. Extended Address (EA) - Used to indicate whether the byte in which the EA value is 1 is the last addressing field.
Devices on each end of a VC can use different DLCIs to identify the same VC. The DLCI values have local significance only, meaning they are only significant to the physical channel on which they reside. Each VC that is multiplexed onto a physical channel will be represented by a unique DLCI. This value identifies and represents the VC * between the FRAD and the Frame Relay switch.
(Click image for larger view in a new window) The termination node performs error detection.įigure 15-13 illustrates the standard Frame Relay frame format.įigure 15-13: Frame Relay Standard Frame Format Error correction detects errors and attempts to correct the condition, usually under control or direction of a higher-layer protocol. NOTE: Error detection detects errors, but does not make attempts to correct the condition. Error correction is left to the upper-layer protocols, such as the TCP (of the TCP/IP protocol suite). Frame Relay error detection uses the CRC checksum to determine if the frame is received by the Frame Relay networking device (router or switch) with, or without, error. Frame Relay services perform error detection rather than error checking error detection is based on the premise that the underlying network media is reliable. Until the first FS exchange occurs, the CPE does not know which DLCIs are active, and as such, no data transfer can take place.įrame Relay uses the Cyclic Redundancy Check (CRC) method for error detection.
FRAME RELAY SIMPLEDIAGRAMS FULL
Approximately every minute, a Full Status (FS) exchange occurs, passing information regarding which DLCIs are configured and active. The LIV also provides information to the network that the CPE is active, and this status is exported at the other end.
FRAME RELAY SIMPLEDIAGRAMS VERIFICATION
A Link Integrity Verification (LIV) packet exchange takes place about every 10 seconds, verifying that the connection is still good. The Frame Relay Customer Premises Equipment (CPE) polls the switch at set intervals to determine the status of both the network and DLCI connections.
FRAME RELAY SIMPLEDIAGRAMS CODE
National Destination Code and Subscriber Number: Up to 14 digits in length (maximum length is dependent on the length of the Country Code).These codes can also be found in any phone book. This code is based on the international telephony numbering plan and can be found in Appendix D, International Country Codes. E.164 addresses are up to 15 digits in length and are structured as follows: E.164 is a hierarchical global telecommunications numbering plan, similar to the North American Number Plan (NANP).These codes can also be found in ITU-T Recommendation X.121. The zone numbers can be found in Appendix C, List of ITU-TX.121 Data Country or Geographical Codes. For example, Zone 2 covers Europe and Zone 3 includes North America). The first digit is a zone number that identifies a part of the world. X.121 addresses are up to 14 digits in length and are structured as follows: X.121 is a hierarchical addressing scheme that was originally designed to number X.25 nodes. Network Consultants Handbook – Frame Relay