P2PSIP J. Rosenberg
Internet-Draft jdrosen.net
Intended status: Standards Track C. Jennings
Expires: December 14, 2011 Cisco
M. Petit-Huguenin
Stonyfish
June 12, 2011
Proportional Quota in REsource LOcation And Discovery (RELOAD)
draft-petithuguenin-p2psip-proportional-quota-00
Abstract
This document defines an extension to RELOAD [I-D.ietf-p2psip-base]
that limits the number of a specific kind element that can be stored
by one RELOAD peer.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Quota Algorithm . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Overlay Configuration Document Extension . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . . 5
Appendix A. Release notes . . . . . . . . . . . . . . . . . . . . 5
A.1. Modifications between
draft-petithuguenin-p2psip-proportional-quota-00 and
draft-petithuguenin-vipr-reload-usage-00 . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
The base specification of RELOAD defines two variables to set the
storage quota. The first one is the maximum size of an element of a
specific kind, the second one is the maximum number of elements of a
specific kind that can be stored on a specific Resource-ID. The
combination of the two variables permits to limit the quantity of
data that a node have to store, as long as these kinds are also
protected by an access control policy that restrict the number of
Resource-IDs that can be used, which is the case for the three access
control policies defined in the base document.
For kinds that are used with an access control policy that does not
restrict the Resource-IDs, a different algorithm is needed to force
storing nodes to behave. This document describes a quota algorithm
that limits the number of elements of a specific kind that a node can
store in the overlay, independently of the Resource-ID used. Another
way to look at this quota algorithm is that an entity must provide a
number of peers that is proportional to the number of elements of a
specific kind that this entity wants to store.
It is important to understand that this quota works only for an
overlay comprising only peers, so with a configuration file
containing a <clients-permitted> element set to false.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Quota Algorithm
A peer responsible for storing kinds using the quota algorithm
described in this document MUST maintain a count of the number of
unique entries being stored per storing peer for each kind. This
operation does not require to add a field containing the Node-ID as
the Node-ID of the storing peer is always available in the signature
field of each element stored.
For example if a peer is storing 5 Resource-IDs and at each of those
5 there are two keys whose first 16 bytes correspond to a particular
Node-ID, it means this node is currently storing 10 unique dictionary
entries for that Node-ID.
When performing the quota checks for an entry, the peer starts by
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verifying that the size of the entry is consistent. It then takes
the <max-count> configuration parameter for this overlay, which
measures the amount of entries of a specific kind a particular node
can store when a <max-count-per>PEER</max-count-per> configuration
parameter is also present. That value is multiplied by by the number
of replicas used by the topology plugin (i.e. 3 for Chord) and then
divided by the fraction of the overlay owned by this peer. If the
result is less than one, it is rounded up to two. This is the
maximum number of unique entries that can be stored for this storing
Node-ID. If the peer is not yet storing this many entries for that
Node-ID, the store is allowed.
Note that when evaluating a Store Request containing multiple entries
per kind, the count of unique entries used for the evaluation is
incremented after each successful check, but the count will be reset
to its initial value if one of the check fails.
The algorithm takes in account only the duplications made by the
topology plugin. If another level of duplication is done at the
application level, the <max-count> value must be adjusted
accordingly.
Note that because of imperfect distribution of Resource-IDs across
the ring, new entries can be rejected even if the total count is
under the limit. It is the responsibility of the storing entity to
calculate the maximum acceptable probability of rejection and to
increase the number of peers accordingly.
4. Overlay Configuration Document Extension
This document extends the overlay configuration document by defining
a new element in the "urn:ietf:params:xml:ns:p2p:quota" namespace.
The <max-count-per> element changes the meaning of the <max-count>
variable. The value "RESOURCE-ID" forces the <max-count> to be
interpreted as been per Resource-ID, which is how the quota is used
when this extension is not used. The value "PEER" forces the <max-
count> to be interpreted as been per peer, which is the algorithm
defined by this document.
The Compact Relax NG Grammar for this element is:
namespace pqt = "urn:ietf:params:xml:ns:p2p:quota"
kind-parameter &= element pqt:max-count-per { max-count-per-type }
max-count-per-type |= "RESOURCE-ID"
max-count-per-type |= "PEER"
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max-count-per-type |= xsd:string # extensions
5. Security Considerations
TBD
6. IANA Considerations
This document adds the following URN to the "XML Namespaces" class of
the "IETF XML Registry":
urn:ietf:params:xml:ns:p2p:quota
7. Acknowledgements
This document was written with the xml2rfc tool described in
[RFC2629].
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[I-D.ietf-p2psip-base]
Jennings, C., Lowekamp, B., Rescorla, E., Baset, S., and
H. Schulzrinne, "REsource LOcation And Discovery (RELOAD)
Base Protocol", draft-ietf-p2psip-base-15 (work in
progress), May 2011.
8.2. Informative References
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
Appendix A. Release notes
This section must be removed before publication as an RFC.
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A.1. Modifications between
draft-petithuguenin-p2psip-proportional-quota-00 and
draft-petithuguenin-vipr-reload-usage-00
o Instead of having a StorageQuota parameter that gives the maximum
number of entries, reused the max-count parameter (that is
mandatory anyway) and changes its meaning.
o Removed the 3x multiplier to account for the application layer
COPY, as it is application specific.
o Removed the additional 3x multiplier to compensate for imperfect
distribution, and moved the responsibility to the storing nodes.
Authors' Addresses
Jonathan Rosenberg
jdrosen.net
Monmouth, NJ
US
Email: jdrosen@jdrosen.net
URI: http://www.jdrosen.net
Cullen Jennings
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Phone: +1 408 421-9990
Email: fluffy@cisco.com
Marc Petit-Huguenin
Stonyfish
Email: marc@stonyfish.com
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