Re: Comments on IPoIB Connected Mode Connection Establ ishment

On Thu, 18 Aug 2005, Jay Rosser wrote:

> Comment inline.
>
>> On Wed, 17 Aug 2005, Dror Goldenberg wrote:
>> 
>>> 
>>> 
>>>> From: Vivek Kashyap [mailto:[email protected]]
>>>> Sent: Monday, August 15, 2005 9:41 AM
>>>> 
>>>> On Wed, 10 Aug 2005, Dror Goldenberg wrote:
>>>> 
>>>>> Reviewing the ipoib-cm draft
>>>>> 
>>>> (http://www1.ietf.org/mail-archive/web/ipoverib/current/msg01372.html
>>>> 
>>>>> 
>>>> <http://www1.ietf.org/mail-archive/web/ipoverib/current/msg013
>>> 
>>> 72.html>
>>> 
>>>>> ) I have three comments about the connection establishment of
>>>>> IPoIB-CM.
>>>>> 
>>>>> (1) Service ID Reserved Bits
>>>>> 
>>>>> Section 3.3. defines the Service-ID as having reserved bits which must
>>>>> be transmitted as zeroes and ignored on receive.
>>>>> It doesn't sound right to ignore those bits on the receive  side.
>>>> 
>>> Ignoring
>>> 
>>>>> those bits on
>>>>> receive essentially means that the IPoIB-CM has to listen on a range of
>>>>> service IDs.
>>>>> I believe that it's better to define a service ID without  reserved bits
>>>> 
>>> such
>>> 
>>>>> that the
>>>>> passive side listens on a single service ID.
>>>>> For example, service IDs defined for SDP, don't have any reserved bits.
>>>> 
>>>> 
>>>> Is it not possible to mask the bits marked as reserved (or
>>>> unused)? The draft requires that the reserved bits must be
>>>> zeroes on send. If it is a limitation
>>>> of the connection manager that it cannot mask the bits and
>>>> will have to listen to the 'range' then I agree that the
>>>> service-ID will have to be specified
>>>> received as zeroes instead of ignoring them.
>>>> 
>>> 
>>> The CM interface is not defined in the IB spec, it is therefore
>>> implementation
>>> dependent. My understanding is that in OpenIB, the Linux CM is capable of
>>> masking the Service ID, but the Windows CM is not. I personally think that
>>> we should define those reserved as zero in send and receive, unless we
>>> can come up with an example of how future extension can leverage
>>> this feature.
>> 
>> 
>> ok, we might have to therefore check for zeros. Does anyone have
>> experience with  Solaris, HP/UX, other CM's?
>
> The HP-UX CM does not currently support masking ServiceIDs and thus cannot 
> support reserved bits in the UC IPoIB ServiceID.
>
> Jay

ok. I'll update the text.

Vivek

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