Re: Proposal for accomodating 10.0000 and 9.58464 line rates
Have you examined the payload of the 4 STS-48c's. After you take out the overhead and stuff bytes, you will have the same payload transfer rate as and OC192C. Otherwise the mapping of OC48 payloads would not mux properly into OC192 payloads.
"Rigsbee, Everett O" wrote:
> Dan, Has anyone considered that you can configure an OC-192 as 4 STS-48c's instead of 64 STS-3c's and thereby boost the payload rate to 9.6192 Gb/s by reducing the redundant overhead bytes. This would also simplify the multiplexing interface to some multiple of 4 bytes (factors of 3 are always messy).
> Thanx, Buzz
> Dr. Everett O. (Buzz) Rigsbee
> Boeing SSG
> PO Box 3707, M/S: 7M-FM
> Seattle, WA 98124-2207
> Ph: (425) 865-2443
> Fx: (425) 865-6721
> Email: everett.o.rigsbee@xxxxxxxxxx
> From: NetWorthTK@xxxxxxx [SMTP:NetWorthTK@xxxxxxx]
> Sent: Tuesday, August 03, 1999 9:14 PM
> To: dan_dove@xxxxxx; stds-802-3-hssg@xxxxxxxx
> Subject: Re: Proposal for accomodating 10.0000 and 9.58464 line rates
> Thanks very much for your patience in replaying my questions. I agree with your comments. However, there are questions to which you may wish to respond:
> > We will need buffers in the PHY to accomodate the difference in MAC and link speeds. I assume this will necessary anyway to allow for some latency in the framing process.
> I agree we need buffers. Using the numbers we are discussing, 10.000 Gbps +/- 100ppm and 9. 58464 Gbps +/- 100 ppm at the maximum frame size of 1500 bytes, the worst case timing skew due to the data rate difference is 6.53ns. In other words, if the MAC/PLS and PHY interface is a byte-wide, the buffer size we need is 66 bits deep (byte) FIFO. I believe Steve has mentioned before a short buffer, 64 bit deep.
> The buffer size is small; therefore, buffer is not an issue at all. On the other hands, if we make all IPG 64 bytes (or 66 bytes the worst case) in conjunction with 66 bit deep byte-buffer, theoretically, we are in good shape without any additional flow control. Although the small packet, 64 byte, will slow down to ½ of the maximum throughput. Is this suggestion causing other deficiencies?
> > I am in support of a MAC/PLS interface that is un-coded data (as Shimon suggested) and will therefore allow PHYs that use different coding for their different environments. It is entirely reasonable to believe that the coding requirements for a 40Km link will be different than those of a 20m copper link.
> I agree. I do not have any qualm with this.
> Edward S. Chang
> NetWorth Technologies, Inc.
> NetworthTK@xxxxxxx <mailto:NetworthTK@xxxxxxx>