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Versions: (draft-maenpaa-p2psip-service-discovery) 00 01 02 03 04 05 06 08 09 10 11 12 13 14 15 RFC 7374

P2PSIP Working Group                                          J. Maenpaa
Internet-Draft                                              G. Camarillo
Intended status: Standards Track                                Ericsson
Expires: July 9, 2012                                    January 6, 2012


  Service Discovery Usage for REsource LOcation And Discovery (RELOAD)
               draft-ietf-p2psip-service-discovery-04.txt

Abstract

   REsource LOcation and Discovery (RELOAD) does not define a generic
   service discovery mechanism as part of the base protocol.  This
   document defines how the Recursive Distributed Rendezvous (ReDiR)
   service discovery mechanism used in OpenDHT can be applied to RELOAD
   overlays to provide a generic service discovery mechanism.

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 9, 2012.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Introduction to ReDiR  . . . . . . . . . . . . . . . . . . . .  4
   4.  Using ReDiR in a RELOAD Overlay Instance . . . . . . . . . . .  6
     4.1.  Data Structure . . . . . . . . . . . . . . . . . . . . . .  6
     4.2.  Selecting the Starting Level . . . . . . . . . . . . . . .  7
     4.3.  Service Provider Registration  . . . . . . . . . . . . . .  7
     4.4.  Refreshing Registrations . . . . . . . . . . . . . . . . .  8
     4.5.  Service Lookups  . . . . . . . . . . . . . . . . . . . . .  8
     4.6.  Removing Registrations . . . . . . . . . . . . . . . . . .  9
   5.  Access Control Rules . . . . . . . . . . . . . . . . . . . . .  9
   6.  REDIR Kind Definition  . . . . . . . . . . . . . . . . . . . . 10
   7.  Example  . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   8.  Overlay Configuration Document Extension . . . . . . . . . . . 12
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
     10.1. Access Control Policies  . . . . . . . . . . . . . . . . . 13
     10.2. Data Kind-ID . . . . . . . . . . . . . . . . . . . . . . . 13
     10.3. ReDiR Namespaces . . . . . . . . . . . . . . . . . . . . . 13
   11. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 13
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 14
     12.2. Informative References . . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14

























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1.  Introduction

   REsource LOcation And Discovery (RELOAD) [I-D.ietf-p2psip-base] is a
   peer-to-peer signaling protocol that can be used to maintain an
   overlay network, and to store data in and retrieve data from the
   overlay.  Although RELOAD defines a Traversal Using Relays around
   Network Address Translation (TURN) specific service discovery
   mechanism, it does not define a generic service discovery mechanism
   as part of the base protocol.  This document defines how the
   Recursive Distributed Rendezvous (ReDiR) service discovery mechanism
   [Redir] used in OpenDHT can be applied to RELOAD overlays.

   In a Peer-to-Peer (P2P) overlay network such as a RELOAD Overlay
   Instance, the peers forming the overlay share their resources in
   order to provide the service the system has been designed to provide.
   The peers in the overlay both provide services to other peers and
   request services from other peers.  Examples of possible services
   peers in a RELOAD Overlay Instance can offer to each other include a
   TURN relay service, a voice mail service, a gateway location service,
   and a transcoding service.  Typically, only a small subset of the
   peers participating in the system are providers of a given service.
   A peer that wishes to use a particular service faces the problem of
   finding peers that are providing that service from the Overlay
   Instance.

   A naive way to perform service discovery is to store the Node-IDs of
   all nodes providing a particular service under a well-known key k.
   The limitation of this approach is that it scales linearly in the
   number of nodes that provide the service.  The problem is two-fold:
   the node n that is responsible for service s identified by key k may
   end up storing a large number of Node-IDs and most importantly, may
   also become overloaded since all service lookup requests for service
   s will need to be answered by node n.  An efficient service discovery
   mechanism does not overload the nodes storing pointers to service
   providers.  In addition, the mechanism must ensure that the load of
   providing a given service is distributed evenly among the nodes
   providing the service.

   ReDiR implements service discovery by building a tree structure of
   the nodes that provide a particular service and embedding it into the
   RELOAD Overlay Instance using RELOAD Store and Fetch requests.  Each
   service provided in the Overlay Instance has its own tree.  The nodes
   in a ReDiR tree contain pointers to service providers.  During
   service discovery, a peer wishing to use a given service fetches
   ReDiR tree nodes one-by-one from the RELOAD Overlay Instance until it
   finds a service provider responsible for its Node-ID.  It has been
   proved that ReDiR can find a service provider using only a constant
   number of Fetch operations [Redir].



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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 RFC 2119 [RFC2119].

   This document uses the terminology and definitions from the Concepts
   and Terminology for Peer to Peer SIP [I-D.ietf-p2psip-concepts]
   draft.


   DHT:  Distributed Hash Tables (DHTs) are a class of decentralized
      distributed systems that provide a lookup service similar to a
      hash table.  Given a key, any participating peer can retrieve the
      value associated with that key.  The responsibility for
      maintaining the mapping from keys to values is distributed among
      the peers.

   H(x):  Hash calculated over x.

   I(l,k):  The unique interval at level l in the ReDiR tree that
      encloses key k.

   n.id:  Node-ID of node n.

   Namespace:  An arbitrary identifier that identifies a service
      provided in the RELOAD Overlay Instance.  An example of a
      namespace is "voice-mail".  The namespace is an UTF-8 text string.

   numBitsInNodeId:  Number of bits in a Node-ID.

   ReDiR tree:  A tree structure of the nodes that provide a particular
      service.  The nodes embed the ReDiR tree into the RELOAD Overlay
      Instance using RELOAD Store and Fetch requests.

   Successor:  The successor of identifier k in namespace ns is the node
      that has joined ns whose identifier most immediately follows k.



3.  Introduction to ReDiR

   Recursive Distributed Rendezvous (ReDiR) [Redir] does not require new
   functionality from the RELOAD base protocol.  This is possible since
   ReDiR interacts with the RELOAD overlay through a put/get API using
   RELOAD Store and Fetch requests.  ReDiR builds a tree structure of
   the nodes that provide a particular service and embeds it into the
   RELOAD Overlay Instance using the Store and Fetch requests.  ReDiR



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   performs lookup in a logarithmic number of Fetch operations with high
   probability.  Further, if the tree's height is estimated based on
   past lookups, the average lookup can be reduced to a constant number
   of Fetch operations assuming that Node-IDs are distributed uniformly
   at random.

   In ReDiR, each service provided in the overlay is identified by an
   arbitrary identifier, called its namespace.  All service providers
   join a namespace and peers wishing to use a service perform lookups
   within the namespace of the service.  A ReDiR lookup for identifier k
   in namespace ns returns a node that has joined ns whose identifier is
   the closest successor of k.

   Each tree node in the ReDiR tree contains a list of Node-IDs of peers
   providing a particular service.  Each node in the tree has a level.
   The root is at level 0, the immediate children of the root are at
   level 1, and so forth.  The ReDiR tree has a branching factor, whose
   value is determined by a new element in the RELOAD overlay
   configuration document, called branching-factor.  At every level i in
   the tree, there are at most branching-factor^i nodes.  The nodes at
   any level are labeled from left to right, such that a pair (i,j)
   uniquely identifies the jth node from the left at level i.  This tree
   is embedded into the RELOAD Overlay Instance node by node, by storing
   the values of node (i,j) at key H(namespace,i,j).  As an example, the
   root of the tree for a voice mail service is stored at H("voice-
   mail",0,0).  Each node (i,j) in the tree is associated with
   branching-factor intervals of the DHT keyspace as follows:

             [2^numBitsInNodeID*b^(-i)*(j+(b'/b)),
              2^numBitsInNodeID*b^(-i)*(j+((b'+1)/b))), for 0<=b'<b,

   where b is the branching-factor.

   Figure 1 shows an example of a ReDiR tree with a branching factor of
   2.  Each node is shown as two horizontal lines separated by a
   vertical bar.  The lines represent the two intervals each node is
   responsible for.  At level 0, there is only one node, (0,0)
   responsible for two intervals that together cover the entire
   identifier space of the RELOAD Overlay Instance.  At level 1, there
   are two nodes, (1,0) and (1,1), each of which is responsible for half
   of the identifier space.  At level 2, there are four nodes.  Each of
   them owns one fourth of the identifier space.  At level 3, there are
   eight nodes each of which is responsible for one eight of the
   identifier space.







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     Level 0  __________________|__________________
                      |                   |
     Level 1  ________|________   ________|________
                 |         |         |         |
     Level 2  ___|___   ___|___   ___|___   ___|___
               |   |     |   |     |   |     |   |
     Level 3  _|_ _|_   _|_ _|_   _|_ _|_   _|_ _|_


                           Figure 1: ReDiR tree


4.  Using ReDiR in a RELOAD Overlay Instance

4.1.  Data Structure

   ReDiR tree nodes are stored using the dictionary data model defined
   in RELOAD base [I-D.ietf-p2psip-base].  The data stored is a
   RedirServiceProvider Resource Record:


               enum { none(0), (255) }
                 RedirServiceProviderExtType;

               struct {
                 RedirServiceProviderExtType   type;
                 NodeId                        serviceProvider;
                 opaque                        namespace<0..2^16-1>;
                 uint16                        level;
                 uint16                        node;
                 uint16                        length;

                 select (type) {
                     /* This type may be extended */
                 } extension;

               } RedirServiceProvider;



   The contents of the RedirServiceProvider Resource Record are as
   follows:

   type







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      The type of an extension to the RedirServiceProvider Resource
      Record.  Unknown types are allowed.

   serviceProvider
      The Node-ID of a service provider.

   namespace
      An opaque string containing the namespace.

   level
      The level in the ReDiR tree.

   node
      The position of the node storing this RedirServiceProvider record
      at the current level in the ReDiR tree.

   length
      The length of the rest of the Resource Record.

   extension
      An extension value.  The RedirServiceProvider Resource Record can
      be extended to include for instance service or service provider
      specific information.


4.2.  Selecting the Starting Level

   Before registering as a service provider or performing a service
   lookup, a peer needs to determine the starting level Lstart for the
   registration or lookup operation in the ReDiR tree.  It is
   RECOMMENDED that Lstart is initially set to 2.  In subsequent
   registrations, Lstart MUST be set to the lowest level at which
   registration last completed.

   In the case of service lookups, nodes MUST record the levels at which
   the last 16 service lookups completed and take Lstart to be the mode
   of those depths.

4.3.  Service Provider Registration

   A node MUST use the following procedure to register as a service
   provider in the RELOAD Overlay Instance:

   1.  A node n with Node-ID n.id wishing to register as a service
       provider starts from level Lstart (see Section 4.2 for the
       details on selecting the starting level).  Therefore, node n sets
       level=Lstart.




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   2.  Node n MUST send a RELOAD Fetch request to fetch the contents of
       the tree node associated with I(level,n.id).  An interval I(l,k)
       is defined as the unique interval at level l in the ReDiR tree
       that encloses key k.  The fetch MUST be a wildcard fetch.
   3.  Node n MUST send a RELOAD Store request to add its
       RedirServiceProvider entry to the dictionary stored in the tree
       node associated with I(level,n.id)
   4.  If node n's Node-ID is the numerically lowest or highest among
       the Node-IDs stored in the tree node associated with
       I(Lstart,n.id), node n MUST continue up the tree towards the root
       (level 0), repeating steps 2 and 3.  Node n MUST continue this
       until it reaches either the root or a level at which n.id is not
       the lowest or highest Node-ID in the interval I(level,n.id).
   5.  Node n MUST also walk down the tree through tree nodes associated
       with the intervals I(Lstart,n.id),I(Lstart+1,n.id),..., at each
       step fetching the current contents of the tree node, and storing
       its RedirServiceProvider record if n.id is the lowest or highest
       Node-ID in the interval.  Node n MUST end this downward walk when
       it reaches a level at which it is the only service provider in
       the interval.

   Note that above, when we refer to 'the tree node associated with
   I(l,k)', we mean the entire tree node (that is, all the intervals
   within the tree node) responsible for interval I(l,k).  In contrast,
   I(l,k) refers to a specific interval within a tree node.

4.4.  Refreshing Registrations

   All state in the ReDiR tree is soft.  Therefore, a service provider
   needs to periodically repeat the registration process to refresh its
   RedirServiceProvider Resource Record.  If a record expires, it MUST
   be dropped from the dictionary by the peer storing the tree node.
   Deciding an appropriate lifetime for the RedirServiceProvider
   Resource Records is up to each service provider.  Every service
   provider MUST repeat the entire registration process periodically
   until it leaves the RELOAD Overlay Instance.

   Note that no new mechanisms are needed to keep track of the remaining
   lifetime of RedirServiceProvider records.  The 'storage_time' and
   'lifetime' fields of RELOAD's StoredData structure can be used for
   this purpose in the usual way.

4.5.  Service Lookups

   The purpose of a service lookup on identifier k in namespace ns is to
   find the node that has joined ns whose identifier most immediately
   follows identifier k.




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   A service lookup is similar to the registration operation.  The
   service lookup starts from some level level=Lstart (see Section 4.2
   for the details on selecting the starting level).  At each step, the
   node n wishing to discover a service provider MUST fetch the tree
   node associated with the current interval I(level,n.id) using a
   RELOAD Fetch request and MUST determine where to look next as
   follows:

   1.  If the successor of node n is not present in the tree node
       associated with I(level,n.id), then its successor must occur in a
       larger range of the keyspace.  Node n MUST set level=level-1 and
       try again.
   2.  If n.id is sandwiched between two Node-IDs in I(level,n.id), the
       successor must lie somewhere in I(level,n.id).  Node n MUST set
       level=level+1 and repeat.
   3.  Otherwise, there is a Node-ID s stored in the node associated
       with I(level,n.id) whose identifier succeeds n.id, and there are
       no Node-IDs between n.id and s.  Thus, s must be the closest
       successor of n.id, and the lookup is done.

   Note that above, when we refer to 'the tree node associated with
   I(l,k)', we mean the entire tree node (that is, all the intervals
   within the tree node) responsible for interval I(l,k).  In contrast,
   I(l,k) refers to a specific interval within a tree node.

4.6.  Removing Registrations

   Before leaving the RELOAD Overlay Instance, a service provider MUST
   remove the RedirServiceProvider records it has stored by storing
   exists=False values in their place, as described in
   [I-D.ietf-p2psip-base].


5.  Access Control Rules

   As specified in RELOAD base [I-D.ietf-p2psip-base], every kind which
   is storable in an overlay must be associated with an access control
   policy.  This policy defines whether a request from a given node to
   operate on a given value should succeed or fail.  Usages can define
   any access control rules they choose, including publicly writable
   values.

   ReDiR requires an access control policy that allows multiple nodes in
   the overlay read and write access to the ReDiR tree nodes stored in
   the overlay.  Therefore, none of the access control policies
   specified in RELOAD base [I-D.ietf-p2psip-base] is sufficient.

   This document defines a new access control policy, called NODE-ID-



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   MATCH.  In this policy, a given value MUST be written and overwritten
   only if the the request is signed with a key associated with a
   certificate whose Node-ID is equal to the dictionary key.  In
   addition, provided that exists=TRUE, the Node-ID MUST belong to one
   of the intervals associated with the tree node (the number of
   intervals each tree node has is determined by the branching-factor
   parameter).  Finally, provided that exists=TRUE,
   H(namespace,level,node), where namespace, level, and node are taken
   from the RedirServiceProvider structure being stored, MUST be equal
   to the Resource-ID for the resource.  The NODE-ID-MATCH policy may
   only be used with dictionary types.


6.  REDIR Kind Definition

   This section defines the REDIR kind.

   Name
      REDIR

   Kind IDs
      The Resource Name for the REDIR Kind-ID is created by
      concatenating three pieces of information: namespace, level, and
      node number.  Namespace is a string identifying a service, such as
      "voice-mail".  Level is an integer specifying a level in the ReDiR
      tree.  Node number is an integer identifying a ReDiR tree node at
      a specific level.  The data stored is a RedirServiceProvider
      structure that was defined in Section 4.1.

   Data Model
      The data model for the REDIR Kind-ID is dictionary.  The
      dictionary key is the Node-ID of the service provider.

   Access Control
      The access control policy for the REDIR kind is the NODE-ID-MATCH
      policy that was defined in Section 5.



7.  Example

   Figure 2 shows an example of a ReDiR tree containing information
   about four different service providers whose Node-IDs are 2, 3, 4,
   and 7.  In the example, numBitsInNodeID=4.  Initially, the ReDiR tree
   is empty.






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     Level 0  ____2_3___4_____7_|__________________
                      |                   |
     Level 1  ____2_3_|_4_____7   ________|________
                 |         |         |         |
     Level 2  ___|2_3   4__|__7   ___|___   ___|___
               |   |     |   |     |   |     |   |
     Level 3  _|_ _|3   _|_ _|_   _|_ _|_   _|_ _|_


                     Figure 2: Example of a ReDiR tree

   First, peer 2 whose Node-ID is 2 joins the namespace.  Since this is
   the first registration peer 2 performs, peer 2 sets the starting
   level Lstart to 2, as was described in Section 4.2.  Also all other
   peers in this example will start from level 2.  First, peer 2 fetches
   the contents of the tree node associated with interval I(2,2) from
   the overlay.  Peer 2 also stores its RedirServiceProvider record in
   that tree node.  Since peer 2's Node-ID is the only Node-ID stored in
   the tree node (i.e., peer 2's Node-ID fulfills the condition that it
   is the numerically lowest or highest among the keys stored in the
   node), peer 2 continues up the tree.  In fact, peer 2 continues up in
   the tree all the way to the root inserting its own Node-ID in all
   levels since the tree is empty (which means that peer 2's Node-ID
   always fulfills the condition that it is the numerically lowest or
   highest Node-ID in the interval I(level, 2) during the upward walk).
   As described in Section 4.3, peer 2 also walks down the tree.  The
   downward walk peer 2 does ends at level 2 since peer 2 is the only
   node in its interval at that level.

   The next peer to join the namespace is peer 3, whose Node-ID is 3.
   Peer 3 starts from level 2.  At that level, peer 3 stores its
   RedirServiceProvider record in the same interval I(2,3) that already
   contains the Node-ID of peer 2.  Since peer 3 has the numerically
   highest Node-ID in the tree node associated with I(2,3), peer 3
   continues up the tree.  Peer 3 stores its RedirServiceProvider record
   also at levels 1 and 0 since its Node-ID is numerically highest among
   the Node-IDs stored in the intervals to which its own Node-ID
   belongs.  Peer 3 also does a downward walk which starts from level 2
   (i.e., the starting level).  Since peer 3 is not the only node in
   interval I(2,3), it continues down the tree to level 3.  The downward
   walk ends at this level since peer 3 is the only service provider in
   the interval I(3,3).

   The third peer to join the namespace is peer 7, whose Node-ID is 7.
   Like the two earlier peers, also peer 7 starts from level 2 because
   this is the first registration it performs.  Peer 7 stores its
   RedirServiceProvider record at level 2.  At level 1, peer 7 has the
   numerically highest (and lowest) Node-ID in its interval I(1,7)



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   (because it is the only node in interval I(1,7); peers 2 and 3 are
   stored in the same tree node but in a different interval) and
   therefore it stores its Node-ID in the tree node associated with that
   interval.  Peer 7 also has the numerically highest Node-ID in the
   interval I(0,7) associated with its Node-ID at level 0.  Finally,
   peer 7 performs a downward walk, which ends at level 2 because peer 7
   is the only node in its interval at that level.

   The final peer to join the ReDiR tree is peer 4, whose Node-ID is 4.
   Peer 4 starts by storing its RedirServiceProvider record at level 2.
   Since it has the numerically lowest Node-ID in the tree node
   associated with interval I(2,4), it continues up in the tree to level
   1.  At level 1, peer 4 stores its record in the tree node associated
   with interval I(1,4) because it has the numerically lowest Node-ID in
   that interval.  Next, peer 4 continues to the root level, at which it
   stores its RedirServiceProvider record and finishes the upward walk
   since the root level was reached.  Peer 4 also does a downward walk
   starting from level 2.  The downward walk stops at level 2 because
   peer 4 is the only peer in the interval I(2,4).


8.  Overlay Configuration Document Extension

   This document extends the RELOAD overlay configuration document by
   adding a new element "branching-factor" inside the new "REDIR" kind
   element:


   redir:branching-factor:  The branching factor of the ReDir tree.  The
      default value is 10.


   This new element is formally defined as follows:

   namespace redir = "urn:ietf:params:xml:ns:p2p:service-discovery"

   parameter &= element redir:branching-factor { xsd:unsignedInt }

   The 'redir' namespace is added into the <mandatory-extension> element
   in the overlay configuration file.


9.  Security Considerations

   There are no new security considerations introduced in this document.
   The security considerations of RELOAD [I-D.ietf-p2psip-base] apply.





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10.  IANA Considerations

10.1.  Access Control Policies

   This document introduces one additional access control policy to the
   "RELOAD Access Control Policy" Registry:

                  NODE-ID-MATCH


   This access control policy was described in Section 5.

10.2.  Data Kind-ID

   This document introduces one additional data Kind-ID to the "RELOAD
   Data Kind-ID" Registry:

                  +--------------+------------+----------+
                  | Kind         |    Kind-ID |      RFC |
                  +--------------+------------+----------+
                  | REDIR        |        104 | RFC-AAAA |
                  +--------------+------------+----------+


   This Kind-ID was defined in Section 6.

10.3.  ReDiR Namespaces

   IANA SHALL create a "ReDiR Namespaces" Registry.  Entries in this
   registry are strings denoting ReDiR namespace values.  The initial
   contents of this registry are:

                  +----------------+----------+
                  | Namespace      |      RFC |
                  +----------------+----------+
                  | turn-server    | RFC-AAAA |
                  +----------------+----------+
                  | voice-mail     | RFC-AAAA |
                  +----------------+----------+



11.  Acknowledgments

   The authors would like to thank Marc Petit-Huguenin for his comments
   on the draft.





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12.  References

12.1.  Normative References

   [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-19 (work in
              progress), October 2011.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

12.2.  Informative References

   [I-D.ietf-p2psip-concepts]
              Bryan, D., Matthews, P., Shim, E., Willis, D., and S.
              Dawkins, "Concepts and Terminology for Peer to Peer SIP",
              draft-ietf-p2psip-concepts-04 (work in progress),
              October 2011.

   [Redir]    Rhea, S., Godfrey, P., Karp, B., Kubiatowicz, J.,
              Ratnasamy, S., Shenker, S., Stoica, I., and H. Yu, "Open
              DHT: A Public DHT Service and Its Uses".


Authors' Addresses

   Jouni Maenpaa
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   Email: Jouni.Maenpaa@ericsson.com


   Gonzalo Camarillo
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   Email: Gonzalo.Camarillo@ericsson.com







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