One document matched: draft-ietf-p2psip-service-discovery-07.txt
Differences from draft-ietf-p2psip-service-discovery-06.txt
P2PSIP Working Group J. Maenpaa
Internet-Draft G. Camarillo
Intended status: Standards Track Ericsson
Expires: August 20, 2013 February 16, 2013
Service Discovery Usage for REsource LOcation And Discovery (RELOAD)
draft-ietf-p2psip-service-discovery-07.txt
Abstract
REsource LOcation and Discovery (RELOAD) does not define a generic
service discovery mechanism as a 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
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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 August 20, 2013.
Copyright Notice
Copyright (c) 2013 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
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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 . . . . . . . . . . . . . . 8
4.4. Refreshing Registrations . . . . . . . . . . . . . . . . . 8
4.5. Service Lookups . . . . . . . . . . . . . . . . . . . . . 9
4.6. Removing Registrations . . . . . . . . . . . . . . . . . . 10
5. Access Control Rules . . . . . . . . . . . . . . . . . . . . . 10
6. REDIR Kind Definition . . . . . . . . . . . . . . . . . . . . 11
7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. Service Registration . . . . . . . . . . . . . . . . . . . 11
7.2. Service Lookup . . . . . . . . . . . . . . . . . . . . . . 13
8. Overlay Configuration Document Extension . . . . . . . . . . . 14
9. Security Considerations . . . . . . . . . . . . . . . . . . . 14
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
10.1. Access Control Policies . . . . . . . . . . . . . . . . . 14
10.2. Data Kind-ID . . . . . . . . . . . . . . . . . . . . . . . 14
10.3. ReDiR Namespaces . . . . . . . . . . . . . . . . . . . . . 15
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
12.1. Normative References . . . . . . . . . . . . . . . . . . . 15
12.2. Informative References . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
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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 a 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): An 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
belonging to 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 height of the ReDiR tree is estimated
based on lookups carried out previously, 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
identifier, called the namespace. All service providers of a given
service join the namespace of that service. Peers wishing to use a
service perform lookups within the namespace of the service. The
result of a ReDiR lookup for an identifier k in namespace ns is a
RedirServiceProvider structure (see Section 4.1) of a service
provider that belongs to ns and whose Node-ID is the closest
successor of identifier k in the namespace.
Each tree node in the ReDiR tree contains a dictionary of
RedirServiceProvider entries of peers providing a particular service.
Each tree node in the ReDiR tree also belongs to some level in the
tree. The root node of the ReDiR tree is located at level 0. The
child nodes of the root node are located at level 1 of the ReDiR
tree. The children of the tree nodes at level 1 are located at level
2, 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 l in the ReDiR
tree, there is room for a maximum of branching-factor^l tree nodes.
As an example, in a tree whose branching-factor is 2, the second
level can contain up to 4 tree nodes (note that a given level may
contain less than the maximum number of tree nodes since empty tree
nodes are not stored). Each tree node in the ReDiR tree is uniquely
identified by a pair (l,j), where l is a level in the ReDiR tree and
j is the position of the tree node (from the left) at that level. As
an example, the pair (2,3) identifies the 3rd tree node from the left
at level 2.
The ReDiR tree is stored into the RELOAD Overlay Instance tree node
by tree node, by storing the values of tree node (level,j) at key
H(namespace,level,j). As an example, the root of the tree for a
voice mail service is stored at H("voice-mail",0,0). Each node
(level,j) in the ReDiR tree contains b intervals of the DHT's
identifier space as follows:
[2^numBitsInNodeID*b^(-level)*(j+(b'/b)),
2^numBitsInNodeID*b^(-level)*(j+((b'+1)/b))), for 0<=b'<b,
where b is the branching-factor.
Figure 1 shows an example of a ReDiR tree whose branching factor is
2. Each tree node is shown as two horizontal lines separated by a
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vertical bar in the middle. 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 of the RELOAD Overlay Instance. 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.
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;
Destination destination_list<0..2^16-1>;
opaque namespace<0..2^16-1>;
uint16 level;
uint16 node;
uint16 length;
select (type) {
/* This type may be extended */
} extension;
} RedirServiceProvider;
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The contents of the RedirServiceProvider Resource Record are as
follows:
type
The type of an extension to the RedirServiceProvider Resource
Record. Unknown types are allowed.
destination_list
A list of IDs through which a message is to be routed to reach the
service provider. The destination list consists of a sequence of
Destination values. The contents of the Destination structure are
as defined in RELOAD base [I-D.ietf-p2psip-base].
namespace
An opaque UTF-8 encoded 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 set to 2. In subsequent registrations,
Lstart MAY, as an optimization, be set to the lowest level at which a
registration operation has last completed.
In the case of subsequent service lookups, nodes MAY, as an
optimization, record the levels at which the last 16 service lookups
completed and take Lstart to be the mode of those depths.
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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 a starting level Lstart (see Section 4.2 for
the details on selecting the starting level). Therefore, node n
sets level=Lstart.
2. Node n MUST send a RELOAD Fetch request to fetch the contents of
the tree node responsible for I(level,n.id). An interval I(l,k)
is the interval at level l in the ReDiR tree that includes 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 responsible for I(level,n.id)
4. If node n's Node-ID (n.id) is the lowest or highest Node-ID
stored in the tree node responsible for I(Lstart,n.id), node n
MUST reduce the current level by one (i.e., set level=level-1)
and continue up the ReDiR tree towards the root level (level 0),
repeating the steps 2 and 3 above. Node n MUST continue in this
way until it reaches either the root of the tree 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 perform a downward walk in the ReDiR tree,
during which it goes through the tree nodes responsible for
intervals I(Lstart,n.id), I(Lstart+1,n.id), I(Lstart+2,n.id),
etc. At each step, node n MUST fetch the responsible tree node,
and store its RedirServiceProvider record in that tree node if
n.id is the lowest or highest Node-ID in its interval. Node n
MUST end this downward walk as soon as it reaches a level l at
which it is the only service provider in its interval I(l,n.id).
Note that above, when we refer to 'the tree node responsible for
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.
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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 for identifier k in namespace ns is
to find the node that is a part of ns and whose identifier most
immediately follows (i.e., is the closest successor of) the
identifier k.
A service lookup is similar to the service registration operation
described in Section 4.3. Service lookups start from a given
starting level level=Lstart in the ReDiR tree (see Section 4.2 for
the details on selecting the starting level). At each step, a node n
wishing to discover a service provider MUST fetch the tree node
responsible for the interval I(level,n.id) that encloses the search
key n.id at the current level using a RELOAD Fetch request. Having
fetched the tree node, node n MUST determine the next action to carry
out as follows:
1. If there is no successor of node n present in the just fetched
ReDiR tree node (note: within the entire tree and not only within
the current interval) responsible for I(level,n.id), then the
successor of node n must be present in a larger segment of the
identifier space (i.e., further up in the ReDiR tree where each
interval and tree node covers a larger range of the identifier
space). Therefore, node n MUST reduce the current level by one
to level=level-1 and carry out a new Fetch operation for the tree
node responsible for n.id at that level. The fetched tree node
is then analyzed and the next action determined by checking
conditions 1-3.
2. If n.id is neither the lowest nor the highest Node-ID within the
interval (note: within the interval, not within the entire tree
node) I(level,n.id), n MUST next check the tree node responsible
for n.id at the next level down the tree. Thus, node n MUST
increase the level by one to level=level+1 and carry out a new
Fetch operation at that level. The fetched tree node is then
analyzed and the next action determined by checking conditions
1-3.
3. If neither of the conditions above holds, meaning that there is a
successor s of n.id present in the just fetched ReDiR tree node
and n.id is the highest or lowest Node-ID in its interval, the
service lookup has finished successfully and s must be the
closest successor of n.id in the ReDiR tree.
Note that above, when we refer to 'the tree node responsible for
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interval 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.
Note also that there may be some cases in which no successor can be
found from the ReDiR tree. An example is a situation in which all of
the service providers stored in the ReDiR tree have a Node-ID smaller
than identifier k. In this case, the upward walk of the service
lookup will reach the root of the tree without encountering a
successor. An appropriate strategy in this case is to pick one of
the RedirServiceProvider entries stored in the dictionary of the root
node at random.
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-
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.
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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 an opaque UTF-8 encoded string
identifying a service, such as "turn-server". 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. Examples
7.1. Service Registration
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; Figure 2 shows the state of the tree at the point when all
the service providers have registered.
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
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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 RELOAD Overlay Instance. This tree node is the first tree node
from the left at Level 2 since key 2 is associated with the second
interval of the first tree node. 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 in Section 4.3 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 entry in the same interval I(2,3) that already
contains the RedirServiceProvider entry of peer 2. Interval I(2,3),
that is, the interval at Level 2 enclosing key 3, is associated with
the right hand side interval of the first tree node. 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)
(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
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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).
7.2. Service Lookup
This subsection gives an example of peer 5 whose Node-ID is 5
performing a service lookup operation in the ReDiR tree shown in
Figure 2. This is the first service lookup peer 5 carries out and
thus the service lookup starts from the default starting level 2. As
the first action, peer 5 fetches the tree node corresponding to the
interval I(2,5) from the starting level. This interval maps to the
second tree node from the left at level 2 since that tree node is
responsible for the interval (third interval from left) to which
Node-ID 5 falls at level 2. Having fetched the tree node, peer 5
checks its contents. First, there is a successor, peer 7, present in
the tree node. Therefore, condition 1 of Section 4.5 is false and
there is no need to perform an upward walk. Second, Node-ID 5 is the
highest Node-ID in its interval, so condition 2 of Section 4.5 is
also false and there is no need to perform a downward walk. Thus,
the service lookup finishes at level 2 since Node-ID 7 is the closest
successor of peer 5.
Note that the service lookup procedure would be slightly different if
peer 5 used level 3 as the starting level. Peer 5 might use this
starting level for instance if it has already carried out service
lookups in the past and follows the heuristic in Section 4.2 to
select the starting level. In this case, peer 5's first action is to
fetch the tree node at level 3 that is responsible for I(3,5). Thus,
peer 5 fetches the third tree node from the left. Since this tree
node is empty, peer 5 decreases the current level by one to 2 and
thus continues up in the tree. The next action peer 5 performs is
identical to the single action in the previous example of fetching
the node associated with I(2,5) from level 2. Thus, the service
lookup finishes at level 2.
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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.
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 |
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+--------------+------------+----------+
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 |
+----------------+----------+
The namespace 'turn-server' is used by nodes that wish to register as
providers of a TURN relay service in the RELOAD overlay and by nodes
that wish to discover providers of a TURN relay service from the
RELOAD overlay.
11. Acknowledgments
The authors would like to thank Marc Petit-Huguenin and Joscha
Schneider for their comments on the draft.
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-24 (work in
progress), January 2013.
[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., Willis, D., Shim, E., Matthews, P., and S.
Dawkins, "Concepts and Terminology for Peer to Peer SIP",
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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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