RE: call 3/4/2015 notes
A bit more on the timestamps.. so 1588 timestamp is:
struct Timestamp
{
UInteger48 secondsField;
UInteger32 nanosecondsField;
};
The catch is that the nanosecondsField field is never greater than 10^9, which again is smaller than 2^30. That means the 2 most significant bits are always 0 or "unused". IMHO we should look into the possibility of just using the nanosecondsField in the RoE header..
The other possible time field could be the time interval:
struct TimeInterval
{
Integer64 scaledNanoseconds;
};
The scaledNanoseconds is always left shifted by 16 bits giving 16 bits of sub-ns accuracy. I am not really sure whether we need such precision.
Just some thoughts after the call.
- Jouni
> -----Original Message-----
> From: stds-1904-3-tf@xxxxxxxx [mailto:stds-1904-3-tf@xxxxxxxx] On Behalf Of
> Jouni Korhonen
> Sent: Thursday, March 05, 2015 10:59 AM
> To: STDS-1904-3-TF@xxxxxxxxxxxxxxxxx
> Subject: call 3/4/2015 notes
>
> Folks,
>
> Start: 3/4/2015 8PM PST
> End: 3/4/2015 9PM PST
>
> Present:
> Jouni Korhonen
> Bomin Li
> Kevin Bross
> Peter Ashwood-Smith
> Raz Gabe
> Jinri Huang
> ??
>
> Discussion:
> * EtherType
> * Packet sizes
> * CRB/VRB flows and their support
> * Sequence numbers & timestamps
>
> Decisions (by consensus):
> * EthType - only one, if further "types" were needed provide equivalent
> functionality
> using subtypes in RoE header.
> * Packet sizes - no recommendations unless someone has good data to backup
> specific numbers. Generic recommendation not to provide numbers
> * CRB/VRB - need to be prepared for VBR flows as a preparation e.g. for
> foreseen
> compressed flows.
> * Sequence Numbers and timestamp:
> - both needed; sequence numbers essential to find out lost packets; field sizes
> to be determined
> - good to have 1588 alignment for timestamp format -> explore how and what
> - timestamp not needed in every packet. More likely e.g. at the
> beginning of each radio frame
> - between timestamps rely on sequence numbers
> - explore whether sequence number and timestamp could use
> the same field; 80 bits is too much though
> - to shorted the size of timestamp look for way to do so
> One proposal to predefine the time reference -> e.g. TAI
> - preferable to allow sub-ns accuracy in the timestamp field
> (like 1588 allows)
>
> Next call: 3/17/2015 at 6AM PST
>
> - Jouni
>
> --
> Jouni Korhonen, Ph.D, Associate Technical Director CTO Office, Networking,
> Broadcom Corporation
> O: +1-408-922-8135, M: +1-408-391-7160