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Cisco ONS 15300 Series

ONS 15327 G1000-2 Card Ports Provisioned with an STS-24c Circuit May Cause CRC Errors


Updated April 15, 2003

February 4, 2003



Products Affected

Product

Top Assembly Part Number

15327-G1000-2

800-18490-01

Problem Description

Release 3.4 includes the G1000 two port Gigabit Ethernet card. An interoperability issue has been discovered during ongoing testing with the 15454 ML-Series cards and the 15327 G1000-2 card. Attempting to send traffic from an ML-Series card at a rate higher than Gigabit Ethernet line rate (1000 Mbps) on an STS-24c circuit may cause Ethernet CRC errors to be generated on the ONS 15327 G1000 card. This may occur if one of the ports is provisioned at STS-24c and the second port begins to carry traffic, at which point the device connected to the first port will begin to see CRC errors. This issue occurs only when one of the two ports on the G1000 card is provisioned at STS-24c rate.

Background

This problem was seen during interoperability testing with the 15454 ML-Series cards. A G1000-2 card on a 15327 was provisioned with (2) 24c SONET circuits. Each circuit was mapped to a separate 15454/ML-Series Card's POS port. Traffic was sent on both SONET circuits in one direction only, from the 15454/ML-Series to the G1000-2 card on the 15327 and then transmitted out the 15327's G1000-2 ports. The first 15454/ML-Series card was setup to send more than gigabit Ethernet line rate traffic (see note below) onto the first 24c SONET circuit feeding into a G1000 port on the 15327. The second 15454/ML-series card was setup to send a smaller amount of traffic (100Mbps) on the second 24c SONET circuit feeding into the same G1000 on the 15327. The 15327's G1000 GigE port that was mapped to the 24c SONET circuit generates approximately 30 Ethernet CRC errors per second (These CRC errors can be seen on the device attached to the G1000 card). The problem disappears if traffic is stopped on the second 24c circuit. The number of CRC errors generated by the first circuit is also proportional to the amount of traffic on the second circuit. When the second circuit's rate was reduced to 10Mbps, the Ethernet CRC error rate reduced to four per second. The second circuit does not have to be a 24c for the problem to be seen. The problem is only affected by having some traffic on the second circuit with the first circuit having greater than Gigabit Ethernet line rate traffic.

Note:?Sending more than Gigabit Ethernet line rate onto a STS-24c circuit can be achieved because of the inherent multiplexing capability on the ML-Series cards. For example, by sending 100Mb on each of the 12 ports of the ML100T-12, the aggregate multiplexed bandwidth is 1.2Gig which can then be transported by the 24c circuit. Scenarios such as this are where the discussed problem arises because the G1000 cards are receiving higher than line rate traffic from the ML-Series card.

Problem Symptoms

The G1000 port provisioned at STS24c generates ethernet CRC errors. This occurs by having some traffic on one circuit and having greater than GigE line rate traffic on the other circuit. The amount of CRC errors generated by one circuit is also proportional to the amount of traffic on the other circuit.

If each of the ports are provisioned at less than STS24c the symptoms will not occur.

Workaround/Solution

Due to the discussed limitation on the G1000 card, avoid mapping more than one ML-Series STS-24c circuit per G1000 card. If an ML-series STS-24c circuit is provisioned to a G1000 card, a second circuit to either an ML card or a different G1000 card should be avoided to prevent these symptoms from occurring.

For More Information

If you require further assistance, or if you have any further questions regarding this field notice, please contact the Cisco Systems Technical Assistance Center (TAC) by one of the following methods: