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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: iSCSI: Login negotiation spacePat, 4k does not make too much sense either with default PDU size of 8k. Are you suggesting we limit this too to a lower value? Your deadlock example while academically correct is not very interesting as I assume that throttling can be done at the first buffer level. Julo
Julian, There is a separate number for cases where very long authentication items are supported and I haven't asked to change that number. Remember the text is: Any iSCSI target or initiator MUST support receiving at least 16384 bytes of key=value data in a negotiation sequence except when indicating support for very long authentication items by offering or selecting authentication methods such as public key certificates in which case they MUST support receiving at least 64 kilobytes of key=value data. Changing the 16384 number on the first line to 4096 will have no effect on the 64 kilobytes limit on the last line and implementations desiring to support very long authentication items are covered.
Julian, A factor of 10 is way overkill. It isn't just 16 k bytes of extra memory. It is n * 16k where n is the number of simultaneous logins the implementation supports - it adds up. The system vendors we work with want to use the memory to do useful work and demand that driver sizes be kept small -- they want the memory available to do "real" work. If 2k doesn't leave enough headroom, then we could live with somewhat more like 4k. If future features added to iSCSI require more space, the drivers that support that can allocate more memory. It is an internal parameter that can be changed when the need arises. There is no future interoperability need to make the buffer oversized in current implementations. Regards, Pat -----Original Message----- From: Julian Satran [mailto:Julian_Satran@il.ibm.com] Sent: Tuesday, July 02, 2002 12:10 AM To: pat_thaler@agilent.com Cc: ips@ece.cmu.edu Subject: RE: iSCSI: Login negotiation space Pat, A factor of 10 over what is needed today is what I would call a conservative design. Limiting the support to 2k would be extremely unwise. And 16 is a tiny amount of memory - of no concern to software implementation and to most hardware implementations. Julo
Julian, 4.1 contains a requirement that initiators and targets support receiving at least 16384 bytes of key=value data (when not supporting very long authentication items). This is overkill and is making drivers larger than they need to be. My calculations are that Security negotiation using the CHAP method (including the Any-stage keys) takes less than 1600 bytes. Operational negotiation requires 1276 bytes (also including the Any-stage keys). All the operational plus security keys are 1911 bytes. Therefore an implementation could hold all the necessary keys in 2 Kbytes. And, the implementation doesn't need to keep the security keys after the security negotiation is done so it could clear some of that out to make room for future keys or vendor specific keys. 16 K bytes is about 10 times the necessary storage in that case. The number of negotiation bytes that a device is required to support should be reduced substantially - preferably to 2048 bytes. Regards, Pat The numbers: 43 AuthMethod CHAP keys 264 Name (no defined size limit - using 255) 11 Algorithm 11 Identifier 264 Challenge 42 Response (for MD5) _____ 635 Chap negotiation length 892 Any-stage keys ---- 1527 Operational negotiation keys 24 HeaderDigest 24 DataDigest 49 MaxConnections 270 TargetName* or InitiatorName* 271 TargetAlias* or InitiatorAlias* 273 TargetAddress* 55 TargetPortalGroupTag* 15 InitialR2T 19 BidiInitialR2T 18 ImmediateData 34 MaxRecvDataSegmentLength 24 MaxBurstLength 26 FirstBurstLength 24 DefaultTime2Wait 26 DefaultTime2Retain 25 MaxOutstandingR2T 18 DataPDUInOrder 24 DataSequenceInOrder 24 ErrorRecoveryLevel 23 SessionType* ------ 892 Any-stage keys 384 Not Any-stage ------ 1276 Operational keys
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