© 2010 Open Grid Forum Choices in Reservation operation 1PC/2PC, timing Tomohiro Kudoh, AIST.

© 2010 Open Grid Forum

Choices in Reservation operation1PC/2PC, timingTomohiro Kudoh, AIST


Reservation options

• 1PC/2PC• 2PC has “held” state, and must be committed

before provisioning

• Start time parameter• Advance / immediate

• Trigger of provisioning• Explicit: signaling message from the root requester• Automatic: Each leaf provider NSA provision at the

specified start time based on its own timer

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Advance reservation (1PC)

3

CoordinatorCohort a Cohort b

reserve

reserve

grantedgranted

I

R


reserve

reserve

not-grantedgranted

roll-back(cancel)

“all” case “none” case

• “Reservation” without “Provisioning” can be roll-back.

• If one of providers (cohorts) can not grant request, coordinator can ask other cohorts to roll-back before provisioning.

I

R

I

R

I

R

I

R

I

R

I

R

I

R

I

R

I: Initial R: Reserved


Immediate reservation (1PC)

4


request

request

grantedgranted

I

P


request

request

not-grantedgranted

roll-back

“all” case “partial” case

• Resources are provisioned when granted• The coordinator cannot ask to cancel before provisioning

I

P

I

P

I

P

I

P

I

P

I

P

I

P

I

P

I: Initial P: Provisioned

Roll-back is not possible (or painful) since the resource is already provisioned.


What is two phase commit protocol?

• An atomic commitment protocol• Used in transaction systems such as data bases• Guarantees all or none of multiple participants

(cohorts) are done (committed).

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commit request

commit request

heldheld

commit commit

I

AH

C

I

AH

C

I

AH

C

I

AH

C

I

AH

C

I

AH

C


commit request

commit request

abortheld

abort

I

AH

C

I

AH

C

I

AH

C

I

AH

C

I

AH

C

I

AH

C


I: Initial H: HeldA: AbortedC: Committed


When is 2PC required?

• 2PC is a protocol to support “roll-back”• A held transaction can be rolled-back

• When a transaction is inherently rolled-back-able, atomic commitment protocol (2PC) is not mandatory

• Usually, “reservation” can be rolled-back, “provisioning” may not.

• Use 2PC when it is required (strongly preferable).

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Immediate reservation with 2PC

• Committed = Provisioned• Roll-back is request before actual

provisioning of resources

7


commit request

commit request

heldheld

commit commit

I

AH

C

I

AH

C

I

AH

C

I

AH

C

I

AH

C

I

AH

C


commit request

commit request

not-grantedheld

abort

I

AH

C

I

AH

C

I

AH

C

I

AH

C

I

AH

C

I

AH

C


I: Initial H: HeldA: AbortedC: Committed


But

• If you do not make a reservation advance enough, the reservation becomes immediate, instead of advance.

• It is not clear how much time is enough. So it is not reasonable to distinguish immediate and advance, and use different protocols.

8


Simplified 2PC

• The cohort which is requested lastly does not have to support 2PC

9


commit request

held

commit

I

AH

C

I

AH

C

I

AH

C

request

granted

I

P

I

P


commit request

held

abort

I

AH

C

I

AH

C

I

AH

C

request

not-granted

I

P

I

P


Chain does not require 2PC between NSAs

• Chain model with 2PC

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NSA

NRM

NSA

NRM

NSA

NRM

2PC 2PC 2PC

• But can be simplified to use 2PC for internal-only • No 2PC is required between NSAs.

NSA

NRM

NSA

NRM

NSA

NRM

2PC

1PC

2PC

1PC

2PC

1PC


Timing issues we should aware

• The following timing issues exist, and must be considered• Reservation time: Time (duration) required to process

request, schedule and make resources ready for provision

• Set up time: Time (duration) between a trigger to provision (signaling message or timer) and the time when service for user become available

• Tear down time: Time (duration) between a trigger to cancel a provision (signaling message or timer) and the time service disappears

• Messaging time: Time (duration) required to deliver a message

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Provisioning timings(1)

• reservation start time• The time a provider NSA starts action to provision

a connection (by timer or signaling)• No preceding processing before this time is

required.

• reservation end time• After this time, provision sequence of another

reservation can be started

• service start/end time• The time the user can start/should finish to use the

connection

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Provisioning timings(2)

ERST Earliest Reservation Start time

reservation must not start before this time to keep ESST (?)

LRST Latest Reservation Start time

reservation must be started by this time to meet the service definition

ERET Earliest Reservation End time

No meaning?

LRET Latest Reservation End time

reservation must be ended by this time to allow next reservation’s provisioning

ESST Earliest Service Start time

service must not start before this time for security reasons.

LSST Latest Service Start time

User requires service by this time

ESET Earliest Service End time

User requires service until this time

LSET Latest Service End time

service must not remain after this time for security reasons

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© 2010 Open Grid Forum 14

LRST

LRET

ESSTLSST

LSET

ESET

LRST ESSTLSST


Parameters of immediate reservation

• There was a discussion on whether to use (start time, end time) or (stat time, duration) for requesting parameters, and we decided to use (start time, end time) for NSI protocol

• They are the same for “exact start time” operation, duration = end time – start time

• But they are different for immediate reservation: (immediate, end time), (immediate, duration)• If the end time is specified, duration of provisioning

is not known, and vice versa.

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© 2010 Open Grid Forum Choices in Reservation operation 1PC/2PC, timing Tomohiro Kudoh, AIST.

Documents

ah c i ah c i ah c request

p i p i p i p i p i

reservation time

p i p slide

time duration

time parameter

messaging time

pc slide