P1394 Mail Archive: Re: P1394> 1394PWG Thick Transport Stack Requirements

P1394 Mail Archive: Re: P1394> 1394PWG Thick Transport Stack Requirements

Re: P1394> 1394PWG Thick Transport Stack Requirements

Toru Ueda (ueda@tansu.slab.tnr.sharp.co.jp)
Wed, 29 Oct 1997 21:16:08 +0900

Hi Brian,

I understand the meaning of buffer service.

If the buffer service provides segmentaion and reassembly,
it may be more useful.
(This might sucrifice the simplicity of buffer service.)

Because IEEE1394 has maximum packet size(512 bytes for S100),
segmentaion and reassembly service may be required if buffer
service treats more than 512 bytes.

Toru Ueda
Software Labs.
Sharp Corporation

>>At 09:54 PM 10/24/97 +0900, Toru Ueda wrote:
>>--
>>--Brian,
>>--
>>--Thank you for forwarding your client requirements for thick
>>--transport stack document.
>>--
>>--I have one question about thick "MUST".
>>--
>>--I don't understand how to use buffer service.
>>--Why must thick transport have buffer service ?
>>
>>The buffer service is used by clients who need to have data delivered with
>>well-defined starting and ending points. For example, this data might be a
>>message that needs to be delivered whole. If a byte stream service is
>>used, the message might be broken into multiple buffers, or if might have
>>other data appended to it. This might make the message impossible to
>>interpret by the receiving service.
>>--My understanding is the transport will handle the
>>--differences of physical buffer sizes of sending and
>>--receiving endpoints.
>>
>>Yes, the transport must handle varying buffer sizes in each direction. For
>>the byte stream service it must be able to break up a large request buffer
>>into multiple send buffers. For the buffer service it must either be able
>>to somehow ommunicate to the client the largest buffer that can be sent or
>>provide buffer segmentation and reassembly services. Maybe this should be
>>added to the requirements?
>>--I assume that the indication of receiving the 30bytes packet
>>--to upper layer will issue when 30bytes data receives whether
>>--this packet is divided into 2-15 bytes or 3-10 bytes data if
>>--the transport packet size is 30 bytes.
>>
>>I think the requirement is that the 30 bytes be delivered as a buffer if
>>the transmitted buffer is 30 bytes and there is some indication that it
>>should be delivered as a single, whole buffer. I don't think it is a
>>requirement that the smaller packets be reassembled into one larger buffer
>>(in other words, that a reassembly service be provided).
>>
>>--But buffer service allows to send only fixed(30bytes in this
>>--case) data.
>>
>>The buffer service would allow UP TO 30 bytes of data to be delivered as a
>>single, whole buffer. A buffer of less than 30 bytes could also be
>>transmitted.
>>
>>--Does this help to write application ?
>>
>>It does help some applications that want to send messages without those
>>messages inherently providing some way to be extracted from a byte stream.
>>
>>--I misunderstand buffer service ?
>>
>>I think that the requirements document is not complete. For now, we
>>probably have many interpretations of the requirements. Our challenge is
>>to refine the requirements list until we all agree on them.
>>
>>Brian
>>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>Brian Batchelder | Hewlett-Packard | mailto:brianb@vcd.hp.com
>>Connectivity Futurist | 1115 SE 164th Ave. | Phone: (360) 212-4107
>>DeskJet Printers | Vancouver, WA 98684 | Fax: (360) 212-4227
>>