Re: XGMII or SPI-4 ?
Wang, what you say is true. The title of the OIF-SPI4-02.0 does say: "...
OC-192 System Interface for the Physical and Link Layer Devices". However,
the OIF considers the SONET/SDH Framer as part of the ISO PHY layer and SPI-4
is the interface between the SONET/SDH Framer and the link layer above it. The
SONET/SDH framer is "like" the Ethernet PHY with respect to the ISO layers.
Note that the OIF specified interface between the SONET/SDH framer and the
SERDES/EO module is the OIF-SFI4-01.0 interface. The SERDES/EO module is "like"
the PMD in 10GbE. There is a good white paper at the OIF web site under Press
Room/OIF White papers that clearly defines SPI and SFI. Tim is not quite
correct, SPI-4 is an interface between the ISO Data Link layer and the ISO
Physical layer (SONET/SDH Framer, Ethernet Phy, etc.) .
Hope this clears up your confusion.
Wang Wendeh wrote:
> Hi Tim,
> Thanks for your comment. But right now I am totally confused.
> Since the document from OIF states clearly that SPI-4 is a service interface
> Link Layer and PHY Layer, I don't know if I misunderstand the meaning or I
> have an
> out-of-date one. Could you educate me about this thing? Thanks a lot.
> Wang, WenDeh
> ----- Original Message -----
> From: Tim Warland <twarland@xxxxxxxxxxxxxxxxxx>
> To: Wang Wendeh <wendeh@xxxxxxxxxxxxx>
> Cc: Ben Brown <bbrown@xxxxxxxx>; stds-802-3-hssg <stds-802-3-hssg@xxxxxxxx>
> Sent: Friday, May 11, 2001 9:11 AM
> Subject: Re: XGMII or SPI-4 ?
> > Wang Wendeh wrote:
> > > Hi Ben,
> > >
> > > Thank you for the valuable information. You mentioned that SPI-4 is an
> > > interface
> > > above MAC layer, so that means the MAC will be needed to be implemented
> > > the PHY device, right? It is kind of different than before. I don't know
> > > it will make
> > > the PHY device to be too complicated.
> > This is not entirely correct. The SPI-4 bus is used for layer 3 traffic.
> > In other word, the data on SPI-4 is TCP/IP packets. In order to get
> > to a PHY which is a layer 1 device, you need to go through a layer
> > 2 device.
> > The purpose of this study group is to define layer 1 and layer 2
> > functional standards for systems implementing ethernet (layer 2)
> > protocals.
> > It is anticipated that component vendors will develop PHY devices
> > with either a XAUI or XSBI (or potentially XGMII) bus interface
> > to a layer 2 MAC device. The system interface from the MAC
> > (which is beyond the scope of this study group) shall be a layer 3
> > type bus such as SPI-4.
> > --
> > Tim Warland P.Eng.
> > Hardware Design Engineer Broadband Products
> > High Performance Optical Component Solutions
> > Nortel Networks (613)765-6634