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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: iSCSI: DLB's Comment on SCSI Port NamesMarjorie, I just wanted some spare in case some other syntactic sugar has to be added. And 223 is 255-32 - In fact I wanted 224 :-) Julo
Julo, I see you've changed to 223 in the draft, serves me right for not responding ;-) I don't understand why you think it's desirable to limit the name length to "something more binary"? And how does 223 accomplish that? Since the port and node names are strings, they are already a "binary length" cause they are a multiple of bytes. I suggest 255 as a max port name length because many string implementations in different languages and OSs can most easily deal with string constructs that are a max of 255 bytes (256 with null terminator). I'm thinking mostly of management applications, since they are the entities that will most have to deal with names for the purpose of assigning resources. From the point of view of the drivers (which I presume are mostly written in C) it doesn't really matter that what the name length is, so I see no value in reducing the max node name to 223 for their benefit. And why 223 anyway, since it's really 238 now that you've limited the representation of the ISID to hex format. > -----Original Message----- > From: Julian Satran [mailto:Julian_Satran@il.ibm.com] > Sent: Saturday, July 13, 2002 7:02 PM > To: ips@ece.cmu.edu > Subject: RE: iSCSI: DLB's Comment on SCSI Port Names > > > Thanks again - I have restricted the encoding of ISID/TPGT to > hex (they are > not both numerical :-)) > Wouldn't it be better to restrict the name length to something more > "binary" like 223? > > Julo > ----- Forwarded by Julian Satran/Haifa/IBM on 07/14/2002 > 04:54 AM ----- > > > > Julian Satran > > > To: > "KRUEGER,MARJORIE (HP-Roseville,ex1)" > <marjorie_krueger@hp.com> > 07/12/2002 04:40 cc: ips > <ips@ece.cmu.edu>, Julian Satran/Haifa/IBM@IBMIL > > AM From: > Julian Satran/Haifa/IBM@Haifa/IBM@IBMIL > > Subject: RE: > iSCSI: DLB's Comment on SCSI Port Names(Document link: Julian > Satran - Mail) > > > > > > > > > > > > > > > > > > > > > > Marjorie, > > Thanks for your complete and timely answer. > > Regards, > Julo > > > > > > "KRUEGER,MARJORIE > > > (HP-Roseville,ex1 To: > Julian Satran/Haifa/IBM@IBMIL > > )" cc: ips > <ips@ece.cmu.edu> > > <marjorie_krueger Subject: RE: > iSCSI: DLB's Comment on SCSI Port Names > > @hp.com> > > > > > > 07/11/2002 05:15 > > > AM > > > Please respond to > > > "KRUEGER,MARJORIE > > > (HP-Roseville,ex1 > > > )" > > > > > > > > > > > > Julo, > I'm a bit confused as the issues list on your website does > not have this as > issue 37, and all I see is issue 9 (where your comment > appears to imply "no > change"?) > > In any case, here's what I recommend: > > In sec 1.1 Definitions change the following definitions to: > > I_T Nexus: the last sentence should be > > The I_T nexus can be identified by the conjunction of the > SCSI port names; > that is, the I_T nexus identifier is the tuple (iSCSI Initiator Name + > ',i,'+ ISID, iSCSI Target Name + ',t,'+ Portal Group Tag). > > SCSI Port Name: definition should be > > A name made up as UTF-8 characters and includes the iSCSI > Name + ',i,' or > ',t,' + ISID or Portal Group Tag > > In sec 2.2.7, 1st paragraph, delete the comment in > parenthesis starting > with "(for iSCSI,.." (or change it to point it to section 2.4.2, your > choice). > > In sec 2.4.2, change the text to: > > When used in SCSI parameter data, the SCSI port name MUST > be encoded as: > - The iSCSI Name in UTF-8 format, followed by > - a comma separator (1 byte), followed by > - the ASCII character 'i' (for SCSI Initiator Port) or the > ASCII character 't' (for SCSI Target Port), followed by > - a comma separator (1 byte), followed by > - A string representation (<numerical-value>, see > section 4.1 Text > Format) > of the ISID (for SCSI initiator port) or the portal > group tag (for > SCSI target port). > SCSI port names have a maximum length of 255 bytes. > The ASCII character 'i' or 't' is the label that > identifies this > port > as either a SCSI Initiator Port or a SCSI Target Port. > The 255 max port name makes for a 237 max iSCSI node name > (check my math > Jim :-) as the max character representation of an ISID is 15 > characters for > the largest decimal representation (14 char for the largest > hex), + 3 char > (",i,") + 237 = 255 > > The change in max node name causes changes to: > > sec 2.2.6.1, paragraph 2, > sec 2.2.6.2, 2nd p, 3rd bullet > > I will see that a change is proposed to Annex A in whatever SAM doc is > currently under revision. > > Thanks, > Marjorie Krueger > Networked Storage Architecture > Networked Storage Solutions Org. > Hewlett-Packard > -----Original Message----- > From: Julian Satran (Actcom) [mailto:Julian_Satran@actcom.net.il] > Sent: Tuesday, July 09, 2002 6:44 AM > To: KRUEGER,MARJORIE (HP-Roseville,ex1); 'Jim Hafner'; > Black_David@emc.com > Cc: ips > Subject: Re: iSCSI: DLB's Comment on SCSI Port Names > > Marjorie, > > I'll list this as issue 37 and I think we can settle on 249 :-) > I would appreciate if you let me know what constants change > (in 2.4.2?) > > Julo > ----- Original Message ----- > From: KRUEGER,MARJORIE (HP-Roseville,ex1) > To: 'Jim Hafner' ; Black_David@emc.com > Cc: ips@ece.cmu.edu > Sent: Tuesday, July 09, 2002 4:04 AM > Subject: RE: iSCSI: DLB's Comment on SCSI Port Names > > I've just encountered this issue with regards to iSCSI port > name encoding > in the SCSI MIB, and the currently specified port name > encoding causes > inconvenience (at best). IMO, it makes sense to be able to treat an > iSCSI name field, be it device name or port name, the same > - as a string > of display characters, portions of which may contain ASCII-encoded > numeric values. > > I don't really see that it makes a difference whether one > views ISID and > TPGT as numeric strings or values, since as Jim says, there are no > calculations performed using these things, and they are basicly just > "tags". The issue for me is that the rest of the "SCSI > port name" is a > string and I see no value in "encoding" the ISID or TPGT as > a value for > SCSI purposes, as SCSI should have no need to use the ISID > or TPGT values > separately from the entire port name. And even if SCSI had > such a need, > it's a simple matter to convert a numeric string representation to a > value. > > The downside of a string-encoding is the increased maximum > size of the > SCSI port name. > > If strings over 256 characters are a problem for some > platforms, I'd be > in favor of reducing the max iSCSI node name to 249 > characters so the > maximum SCSI port name would be 255 characters total (249 > char name + > ",i," + "0x0000") > > Marjorie Krueger > Networked Storage Architecture > Networked Storage Solutions Org. > Hewlett-Packard > -----Original Message----- > From: Jim Hafner [mailto:hafner@almaden.ibm.com] > Sent: Monday, July 08, 2002 9:08 AM > To: Black_David@emc.com > Cc: ips@ece.cmu.edu > Subject: RE: iSCSI: DLB's Comment on SCSI Port Names > > > David, > > I believe it will (may?) be used, so I agree we're in the > second case. > However, this format is the intended use in SCSI protocol > stuff. Two > places where SCSI ports names are used now is in ALIAS, > Access Controls > and in third party reservations -- see caveat below, however) > > I don't see a need in this context to define these as > strings (that's not > a SCSI way of thinking...). > > However, I think the issue comes down to a simple question: > are the ISID > and TPGT values or numerical strings (Julian is calling > them numerical > strings, but I've always thought of them as values, in > spite of the fact > that there is no arithmetic done on them - there is > precedent in SCSI for > such thinking, so I'm not completely out in the woods here). > > If they are values, then I'd like to see them formatted for SCSI in > "value form"; if they are strings, then any representation > should be OK. > > > Does that at least get to the core of the issue? > > Jim Hafner > > CAVEAT: I don't think we'd use the iSCSI constructed port > names in those > contexts as device names are better suited for those > purposes, but these > are examples where specification of SCSI port name format > is required. > > > To: Jim Hafner/Almaden/IBM@IBMUS > cc: ips@ece.cmu.edu > Subject: RE: iSCSI: DLB's Comment on SCSI Port Names > > > > Jim, > > My view of this is that either: > - The SCSI Port Name is never going to be used, in which case > it shouldn't be designed to this level of detail. OR > - It's going to be used, and hence is worth designing in a fashion > that is reasonable to use. > I think we're in the second category, and turning the ISID into > hex ASCII (well, UTF-8) so the SCSI port name is a string is > worth doing now to avoid problems when people actually try > to use it. I would have no problems if someone wanted to > pad the string, but I'd make specifying the padding the > responsibility of the protocol/API/situation in which it > was used rather than incorporating the padding into the name. > > Thanks, > --David > > -----Original Message----- > From: Jim Hafner [mailto:hafner@almaden.ibm.com] > Sent: Monday, July 08, 2002 11:42 AM > To: Black_David@emc.com > Cc: ips@ece.cmu.edu > Subject: Re: iSCSI: DLB's Comment on SCSI Port Names > > > > David, > > You wrote: > > >[T.9] 2.4.2 SCSI Architecture Model > > > > The SCSI Port Name is mandatory in iSCSI. When used in SCSI > > parameter data, the SCSI port name MUST be encoded as: > > - The iSCSI Name in UTF-8 format, followed by > > - a comma separator (1 byte), followed by > > - the ASCII character 'i' (for SCSI Initiator Port) or the > > ASCII character 't' (for SCSI Target Port), followed by > > - a comma separator (1 byte), followed by > > - zero to 3 null pad bytes so that the complete format is a > > multiple of four bytes long, followed by > > - the 6byte value of the ISID (for SCSI initiator port) or the > > 2byte value of the portal group tag (for SCSI target port) in > > network byte order (BigEndian). > > > That's a peculiar format with padding nulls in the middle and > > a number concatenated after the padding - for example, it can't > > be passed in iSCSI login without format conversion. How about > > converting the number to 4 or 12 bytes of hex (ASCII characters) > > and moving the padding to the end so the result is actually a > > string, and excluding the padding from the definition of the name? > > This will increase the maximum length of port names, but produce > > names that are easier to deal with. > > Admittedly that's an odd format, however here was the > reason for this > layout. > 1) it's not used directly in iSCSI "Text" strings; it's > intended to be a > description of how this information is packed into a byte array for > representation in "SCSI parameter data" (as it says!) -- > that is, it's > NEVER > "passed in iSCSI login" (in this form). > 2) the padding after the string was to force the binary > values of the > ISID > or PGT to be better word aligned and can be more easily > extracted as a > value > direct from the byte array without conversion. > > What do you think? > > Jim Hafner > > > > > >
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