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Arista TimeStamp Configuration Examples

Timestamp formats and locations on transit devices

1. Field Overwriting

Many implementations (including optional modes on both the Arista 7150 and 7280 series) take an existing field within a frame header or trailer and replace that value with the hardware timestamp.

2. Self-contained frame trailer

Another implementation to apply the timestamp is to expand the original packet with a set of custom fields. When such an implementation is used the FCS field must be updated to ensure the packet that leaves the device is a valid Ethernet frame that can be forwarded normally by subsequent transit devices.

Timestamping on the Arista 7130 Series

These L1+ devices support sub-nanosecond timestamp precision via the MetaWatch application and are typically implemented as an inline active tap device performing tapping/replication of the production links, or as physically close to the passive tap performing the replication. The active tap function replicates traffic through the system in 5 ns while simultaneously replicating the packets to the MetaWatch application.

Timestamping on the 7150 Series

Timestamping is supported on traffic replicated via a mirror session when the device is used as a production switch, or on ingress traffic when deployed in Tap Aggregation mode.

The 31 bit 7150 timestamp header can be used in both self-contained and overwrite modes. Specifically, the timestamp can be inserted before the FCS in the ethernet trailer or can be configured to overwrite the FCS.

Replacement of the FCS

mac timestamp replace-fcs

Appending of the timestamp

switch(config)#interface ethernet 44
switch(config-if-Et44)#mac timestamp before-fcs
switch(config-if-Et44)#show active
interface Ethernet44
   mac timestamp before-fcs
switch(config-if-Et44)#no mac timestamp
switch(config-if-Et44)#show active
interface Ethernet44


hardware/alista/timestamp.txt ยท Last modified: 2020/09/01 by admin

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