Checking the SONET Frame Checksum
This section includes the following information to assist you when troubleshooting SONET interfaces:
Checklist for Checking the SONET Frame Checksum
Purpose
To check and configure SONET frame checksum.
Action
Table 1 provides the links and commands for SONET frame checksum.
Table 1: Checklist for Checking the SONET Frame Checksum
Tasks | Command or Action |
---|---|
Understand the SONET Frame Checksum | |
Checking the SONET Frame Checksum | |
show interfaces interface-name extensive | |
show configuration interfaces | interface-name | |
Configuring a SONET Frame Checksum | |
[edit] | |
[edit] | |
[edit] |
Understand the SONET Frame Checksum
Problem
Description: The SONET frame checksum is a calculation that is added to a frame for error control purposes. SONET frame checksum is used in High-Level Data Link Control (HDLC), Frame Relay, and other data-link layer protocols. For example, Router A calculates the frame check sequence (FCS) and adds it to the outgoing message. Router B, on receiving the message recalculates the FCS and compares it to the FCS from Router A. If there is a difference, both sides of the connection might not match in relation to the FCS configuration.
Solution
If you are having problems with a connection, check whether the FCS matches on both sides of the connection. To check the SONET frame checksum, see Checking the SONET Frame Checksum.
After you have checked the FCS and determined that a problem exists, you must configure a SONET frame checksum. For more information, see Configuring a SONET Frame Checksum.
Checking the SONET Frame Checksum
If you are having problems with a connection, check that the FCS matches on both sides of the connection.
To check the SONET frame checksum, follow these steps:
Examining Output for Framing Errors
Purpose
By examining the output for an interface, you can determine if framing errors are incrementing in the absence of any SONET alarms or defects.
Action
From the Junos OS command-line interface (CLI) operational mode, use the following command to check for framing errors:
Sample Output
user@router1> show interfaces so-1/0/0 extensive
Physical interface: so-1/0/0, Enabled, Physical link is Up Interface index: 13, SNMP ifIndex: 18, Generation: 12 Link-level type: PPP, MTU: 4474, Clocking: Internal, SONET mode, Speed: OC3, Loopback: None, FCS: 16 , Payload scrambler: Enabled Device flags : Present Running Interface flags: Link-Layer-Down Point-To-Point SNMP-Traps Link flags : Keepalives Hold-times : Up 0 ms, Down 0 ms Keepalive settings: Interval 10 seconds, Up-count 1, Down-count 3 Keepalive statistics: Input : 6 (last seen 00:00:52 ago) Output: 11 (last sent 00:00:05 ago) LCP state: Opened NCP state: inet: Opened, inet6: Not-configured, iso: Opened, mpls: Conf-req-sent CHAP state: Not-configured Last flapped : 2002-11-01 22:28:30 UTC (1w5d 23:26 ago) Statistics last cleared: 2002-11-14 21:52:51 UTC (00:01:50 ago) Traffic statistics: Input bytes : 692 0 bps Output bytes : 716 32 bps Input packets: 23 0 pps Output packets: 72 0 pps Input errors: Errors: 0, Drops: 0, Framing errors: 27 , Runts: 0, Giants: 0, Bucket drops: 0, Policed discards: 0, L3 incompletes: 0, L2 channel errors: 0, L2 mismatch timeouts: 0, HS link CRC errors: 0, HS link FIFO overflows: 0 Output errors: Carrier transitions: 0, Errors: 0, Drops: 0, Aged packets: 0, HS link FIFO underflows: 0 SONET alarms : None SONET defects : None SONET PHY: Seconds Count State PLL Lock 0 0 OK PHY Light 0 0 OK SONET section: BIP-B1 0 0 SEF 0 0 OK LOS 0 0 OK LOF 0 0 OK ES-S 0 SES-S 0 SEFS-S 0 SONET line: BIP-B2 0 0 REI-L 0 0 RDI-L 0 0 OK AIS-L 0 0 OK BERR-SF 0 0 OK BERR-SD 0 0 OK ES-L 0 SES-L 0 UAS-L 0 ES-LFE 0 SES-LFE 0 UAS-LFE 0 SONET path: BIP-B3 0 0 REI-P 0 0 LOP-P 0 0 OK AIS-P 0 0 OK RDI-P 0 0 OK UNEQ-P 0 0 OK PLM-P 0 0 OK ES-P 0 SES-P 0 UAS-P 0 ES-PFE 0 SES-PFE 0 UAS-PFE 0 Received SONET overhead: F1 : 0x00, J0 : 0x00, K1 : 0x00, K2 : 0x00 S1 : 0x00, C2 : 0xcf, C2(cmp) : 0xcf, F2 : 0x00 Z3 : 0x00, Z4 : 0x00, S1(cmp) : 0x00, V5 : 0x00 V5(cmp) : 0x00 Transmitted SONET overhead: F1 : 0x00, J0 : 0x01, K1 : 0x00, K2 : 0x00 S1 : 0x00, C2 : 0xcf, F2 : 0x00, Z3 : 0x00 Z4 : 0x00, V5 : 0x00 Received path trace: router2 so-1/3/1 73 6c 69 70 70 65 72 79 20 73 6f 2d 31 2f 33 2f router2 so-1/3/1 31 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0d 0a ................ Transmitted path trace: router1 so-1/0/0 68 61 69 72 79 20 73 6f 2d 31 2f 30 2f 30 00 00 router1 so-1/0/0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ HDLC configuration: Policing bucket: Disabled Shaping bucket : Disabled Giant threshold: 4484, Runt threshold: 3 Packet Forwarding Engine configuration: Destination slot: 1, PLP byte: 1 (0x00) CoS transmit queue Bandwidth Buffer Priority Limit % bps % bytes 0 best-effort 95 147744000 95 0 low none 3 network-control 5 7776000 5 0 low none Logical interface so-1/0/0.0 (Index 8) (SNMP ifIndex 108) (Generation 9) Flags: Device-Down Point-To-Point SNMP-Traps Encapsulation: PPP Protocol inet, MTU: 4470, Generation: 15, Route table: 1 Flags: Is-Primary Addresses, Flags: Dest-route-down Is-Default Is-Preferred Is-Primary Destination: 1.1.6.1, Local: 1.1.6.2, Broadcast: Unspecified, Generation: 15 Protocol iso, MTU: 4470, Generation: 16, Route table: 1 Flags: Is-Primary Protocol mpls, MTU: 4458, Generation: 17, Route table: 1 Flags: Protocol-Down, Is-Primary
Meaning
The sample output shows that Router 1 is configured for FCS 16, that framing errors have incremented to 27, and that there are no SONET alarms or defects. Incrementing framing errors, in the absence of any SONET alarms or defects, are a symptom of SONET frame checksum errors.
See also
Checking the FCS Configuration
Purpose
If you are having problems with a connection, check your router’s FCS configuration and, if possible, the FCS configuration on the router on the other side of the connection.
Action
From the Junos OS CLI operational mode, use one of the following two commands to check the SONET frame checksum:
or
The option to display a specific configuration with the show configuration command hierarchy was introduced in Junos OS Release 5.3.
Sample Output 1
user@host> show configuration interfaces so-0/0/0
encapsulation cisco-hdlc; sonet-options { fcs 32; payload-scrambler; } unit 0 { family inet { address 10.0.0.2/32 { destination 10.0.0.1; } } family mpls; }
Sample Output 2
user@host> show interfaces so-0/0/1
Physical interface: so-0/0/1, Enabled, Physical link is Up Interface index: 48, SNMP ifIndex: 114 Link-level type: PPP, MTU: 4474, Clocking: Internal, SONET mode, Speed: OC3, Loopback: None, FCS: 32, Payload scrambler: Disabled Device flags : Present Running Interface flags: Point-To-Point SNMP-Traps Link flags : Keepalives Keepalive settings: Interval 10 seconds, Up-count 1, Down-count 3 Keepalive: Input: 70627 (00:00:07 ago), Output: 70791 (00:00:08 ago) LCP state: Opened NCP state: inet: Opened, inet6: Not-configured, iso: Opened, mpls: Not-configured Input rate : 78056456 bps (6504 pps) Output rate : 78044840 bps (6503 pps) SONET alarms : None SONET defects : None Logical interface so-0/0/1.0 (Index 61) (SNMP ifIndex 118) Flags: Point-To-Point SNMP-Traps Encapsulation: PPP Protocol inet, MTU: 4470, Flags: None Addresses, Flags: Is-Preferred Is-Primary Destination: 192.168.50.0/30, Local: 192.168.50.1 Protocol iso, MTU: 4470, Flags: None
Meaning
Sample output 1 shows that FCS 32 is configured. If you use the show configuration or show configuration interfaces command, you must scroll to the particular interface for the FCS configuration status.
Meaning
Sample output 2 shows that FCS 32 is configured. To change the FCS configuration, see Returning to the Default 16-Bit Checksum, Configuring a 16-Bit Checksum, or Configuring a 32-Bit Checksum.
Configuring a SONET Frame Checksum
After you have checked the FCS and determined that a problem exists, you might need to do one of the following, depending on the situation:
By default, SONET interfaces use a 16-bit frame checksum. You can configure a 32-bit checksum, which provides more reliable packet verification. However, some older equipment may not support 32-bit checksums.
Returning to the Default 16-Bit Checksum
Action
To return to the default 16-bit frame checksum, follow these steps:
In configuration mode, go to the following hierarchy level.
[edit]user@host# edit interfaces so-fpc/pic/port sonet-optionsDelete the fcs 32 statement from the configuration.
[edit interfaces interface-name sonet-options]user@host# delete fcs 32Verify the configuration.
[edit interfaces interface-name sonet-options]user@host# showCommit the configuration.
user@host# commit
Configuring a 16-Bit Checksum
Action
To explicitly configure the 16-bit checksum, follow these steps:
In configuration mode, go to the following hierarchy level.
[edit]user@host# edit interfaces so-fpc/pic/port sonet-optionsConfigure the 16-bit checksum.
[edit interfaces so-fpc/pic/port sonet-options]user@host# set fcs 16Verify the configuration.
[edit interfaces interface-name sonet-options]user@host# showfcs 16;Commit the configuration.
user@host# commit
Configuring a 32-Bit Checksum
Action
To explicitly configure the 32-bit checksum, follow these steps:
In configuration mode, go to the following hierarchy level.
[edit]user@host# edit interfaces so-fpc/pic/port sonet-optionsConfigure the 32-bit checksum.
[edit interfaces so-fpc/pic/port sonet-options]user@host# set (fcs 32 | rfc-2615)Note The rfc-2615 statement automatically configures the interface to use FCS 32 and changes the C2 byte to 0x16, as per the RFC.
Verify the configuration.
[edit interfaces interface-name sonet-options]user@host# showfcs 32;or
[edit interfaces interface-name sonet-options]user@host# showrfc-2615;Commit the configuration.
user@host# commitNote On a Channelized OC12 interface, the sonet-options fcs statement is not supported. To configure FCS on each DS3 channel, you must include the t3-options fcs statement in the configuration for each channel.