draft-ietf-p2psip-rpr-02.txt   draft-ietf-p2psip-rpr-03.txt 
P2PSIP N. Zong, Ed. P2PSIP N. Zong, Ed.
Internet-Draft X. Jiang Internet-Draft X. Jiang
Intended status: Standards Track R. Even Intended status: Standards Track R. Even
Expires: November 30, 2012 Huawei Technologies Expires: April 25, 2013 Huawei Technologies
Y. Zhang Y. Zhang
China Mobile China Mobile
May 29, 2012 October 22, 2012
An extension to RELOAD to support Relay Peer Routing An extension to RELOAD to support Relay Peer Routing
draft-ietf-p2psip-rpr-02 draft-ietf-p2psip-rpr-03
Abstract Abstract
This document proposes an optional extension to RELOAD to support This document proposes an optional extension to RELOAD to support
relay peer routing mode. RELOAD recommends symmetric recursive relay peer routing mode. RELOAD recommends symmetric recursive
routing for routing messages. The new optional extension provides a routing for routing messages. The new optional extension provides a
shorter route for responses reducing the overhead on intermediary shorter route for responses reducing the overhead on intermediary
peers and describes the potential cases where this extension can be peers and describes the potential cases where this extension can be
used. used.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 30, 2012. This Internet-Draft will expire on April 25, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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it for publication as an RFC or to translate it into languages other it for publication as an RFC or to translate it into languages other
than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Backgrounds . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Backgrounds . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 5 3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1.1. Relay Peer Routing (RPR) . . . . . . . . . . . . . . . 6 3.1.1. Relay Peer Routing (RPR) . . . . . . . . . . . . . . . 5
3.2. Scenarios Where RPR Benefits . . . . . . . . . . . . . . . 6 3.2. Scenarios Where RPR Benefits . . . . . . . . . . . . . . . 6
3.2.1. Managed or Closed P2P System . . . . . . . . . . . . . 6 3.2.1. Managed or Closed P2P System . . . . . . . . . . . . . 6
3.2.2. Using Bootstrap Peers as Relay Peers . . . . . . . . . 7 3.2.2. Using Bootstrap Peers as Relay Peers . . . . . . . . . 7
3.2.3. Wireless Scenarios . . . . . . . . . . . . . . . . . . 7 3.2.3. Wireless Scenarios . . . . . . . . . . . . . . . . . . 7
4. Relationship Between SRR and RPR . . . . . . . . . . . . . . . 7 4. Relationship Between SRR and RPR . . . . . . . . . . . . . . . 7
4.1. How RPR Works . . . . . . . . . . . . . . . . . . . . . . 7 4.1. How RPR Works . . . . . . . . . . . . . . . . . . . . . . 7
4.2. How SRR and RPR Work Together . . . . . . . . . . . . . . 8 4.2. How SRR and RPR Work Together . . . . . . . . . . . . . . 7
5. Comparison on cost of SRR and RPR . . . . . . . . . . . . . . 8 5. Comparison on cost of SRR and RPR . . . . . . . . . . . . . . 8
5.1. Closed or managed networks . . . . . . . . . . . . . . . . 8 5.1. Closed or managed networks . . . . . . . . . . . . . . . . 8
5.2. Open networks . . . . . . . . . . . . . . . . . . . . . . 9 5.2. Open networks . . . . . . . . . . . . . . . . . . . . . . 9
6. Extensions to RELOAD . . . . . . . . . . . . . . . . . . . . . 9 6. Extensions to RELOAD . . . . . . . . . . . . . . . . . . . . . 9
6.1. Basic Requirements . . . . . . . . . . . . . . . . . . . . 9 6.1. Basic Requirements . . . . . . . . . . . . . . . . . . . . 9
6.2. Modification To RELOAD Message Structure . . . . . . . . . 10 6.2. Modification To RELOAD Message Structure . . . . . . . . . 9
6.2.1. State-keeping Flag . . . . . . . . . . . . . . . . . . 10 6.2.1. State-keeping Flag . . . . . . . . . . . . . . . . . . 10
6.2.2. Extensive Routing Mode . . . . . . . . . . . . . . . . 10 6.2.2. Extensive Routing Mode . . . . . . . . . . . . . . . . 10
6.3. Creating a Request . . . . . . . . . . . . . . . . . . . . 10 6.3. Creating a Request . . . . . . . . . . . . . . . . . . . . 10
6.3.1. Creating a request for RPR . . . . . . . . . . . . . . 10 6.3.1. Creating a request for RPR . . . . . . . . . . . . . . 10
6.4. Request And Response Processing . . . . . . . . . . . . . 11 6.4. Request And Response Processing . . . . . . . . . . . . . 11
6.4.1. Destination Peer: Receiving a Request And Sending 6.4.1. Destination Peer: Receiving a Request And Sending
a Response . . . . . . . . . . . . . . . . . . . . . . 11 a Response . . . . . . . . . . . . . . . . . . . . . . 11
6.4.2. Sending Peer: Receiving a Response . . . . . . . . . . 12 6.4.2. Sending Peer: Receiving a Response . . . . . . . . . . 11
6.4.3. Relay Peer Processing . . . . . . . . . . . . . . . . 12 6.4.3. Relay Peer Processing . . . . . . . . . . . . . . . . 12
7. Discovery Of Relay Peer . . . . . . . . . . . . . . . . . . . 12 7. Discovery Of Relay Peer . . . . . . . . . . . . . . . . . . . 12
8. Optional Methods to Investigate Node Connectivity . . . . . . 12 8. Optional Methods to Investigate Peer Connectivity . . . . . . 12
9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
12.1. Normative References . . . . . . . . . . . . . . . . . . . 14 12.1. Normative References . . . . . . . . . . . . . . . . . . . 14
12.2. Informative References . . . . . . . . . . . . . . . . . . 14 12.2. Informative References . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction 1. Introduction
1.1. Backgrounds 1.1. Backgrounds
RELOAD [I-D.ietf-p2psip-base] recommends symmetric recursive routing RELOAD [I-D.ietf-p2psip-base] recommends symmetric recursive routing
(SRR) for routing messages and describes the extensions that would be (SRR) for routing messages and describes the extensions that would be
required to support additional routing algorithms. Other than SRR, required to support additional routing algorithms. Other than SRR,
two other routing options: direct response routing (DRR) and relay two other routing options: direct response routing (DRR) and relay
peer routing (RPR) are also discussed in Appendix D in [I-D.ietf- peer routing (RPR) are also discussed in Appendix D in [I-D.ietf-
p2psip-base]. DRR is specified in [I-D.ietf-p2psip-drr]. As we show p2psip-base]. DRR is specified in [I-D.ietf-p2psip-drr]. As we show
in section 3, RPR is advantageous over SRR in some scenarios reducing in section 3, RPR is advantageous over SRR in some scenarios reducing
load (CPU and link BW) on intermediary peers . RPR works better in a load (CPU and link BW) on intermediary peers. RPR works better in a
network where relay peers are provisioned in advance so that relay network where relay peers are provisioned in advance so that relay
peers are publicly reachable in the P2P system. In other scenarios, peers are publicly reachable in the P2P system. In other scenarios,
using a combination of RPR and SRR together is more likely to bring using a combination of RPR and SRR together is more likely to bring
benefits than if SRR is used alone. Some discussion on connectivity benefits than if SRR is used alone. Some discussion on connectivity
is in Non-Transitive Connectivity and DHTs is in Non-Transitive Connectivity and DHTs
[http://srhea.net/papers/ntr-worlds05.pdf]. [http://srhea.net/papers/ntr-worlds05.pdf].
Note that in this draft, we focus on RPR routing mode and its Note that in this draft, we focus on RPR routing mode and its
extensions to RELOAD. Some text such as modification to RELOAD extensions to RELOAD. Some text such as modification to RELOAD
message structure, optional methods to investigate node connectivity message structure, optional methods to investigate peer connectivity
described in DRR draft [I-D.ietf-p2psip-drr] are also relevent to described in DRR draft [I-D.ietf-p2psip-drr] are also relevent to
RPR. RPR.
We first discuss the problem statement in Section 3, then how to We first discuss the problem statement in Section 3, then how to
combine RPR and SRR is presented in Section 4. In Section 5, we give combine RPR and SRR is presented in Section 4. In Section 5, we give
comparison on the cost of SRR and RPR in both managed and open comparison on the cost of SRR and RPR in both managed and open
networks. An extension to RELOAD to support RPR is proposed in networks. An extension to RELOAD to support RPR is proposed in
Section 6. Discovery of relay peers is introduced in Section 7. Section 6. Discovery of relay peers is introduced in Section 7.
Some optional methods to check node connectivity is introduced in Some optional methods to check peer connectivity is introduced in
Section 8. Section 8.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
We use the terminology and definitions from the Concepts and We use the terminology and definitions from the Concepts and
Terminology for Peer to Peer SIP [I-D.ietf-p2psip-concepts] draft Terminology for Peer to Peer SIP [I-D.ietf-p2psip-concepts] draft
extensively in this document. We also use terms defined in NAT extensively in this document. We also use terms defined in NAT
behavior discovery [I-D.ietf-behave-nat-behavior-discovery]. Other behavior discovery [RFC5780]. Other terms used in this document are
terms used in this document are defined inline when used and are also defined inline when used and are also defined below for reference.
defined below for reference.
There are two types of roles in the RELOAD architecture: peer and Publicly Reachable: A peer is publicly reachable if it can receive
client. Node is used when describing both peer and client. In unsolicited messages from any other peer in the same overlay. Note:
discussions specific to behavior of a peer or client, the term peer
or client is used instead.
Publicly Reachable: A node is publicly reachable if it can receive "publicly" does not mean that the peers must be on the public
unsolicited messages from any other node in the same overlay. Note:
"publicly" does not mean that the nodes must be on the public
Internet, because the RELOAD protocol may be used in a closed system. Internet, because the RELOAD protocol may be used in a closed system.
Relay Peer: A type of publicly reachable peer that can receive Relay Peer: A type of publicly reachable peer that can receive
unsolicited messages from all other nodes in the overlay and forward unsolicited messages from all other peers in the overlay and forward
the responses from destination peers towards the request sender. the responses from destination peers towards the request sender.
Relay Peer Routing (RPR): refers to a routing mode in which responses Relay Peer Routing (RPR): refers to a routing mode in which responses
to P2PSIP requests are sent by the destination peer to a relay peer to P2PSIP requests are sent by the destination peer to a relay peer
transport address who will forward the responses towards the sending transport address who will forward the responses towards the sending
peer. For simplicity, the abbreviation RPR is used instead in the peer. For simplicity, the abbreviation RPR is used instead in the
following text. following text.
Symmetric Recursive Routing (SRR): refers to a routing mode in which Symmetric Recursive Routing (SRR): refers to a routing mode in which
responses follow the request path in the reverse order to get back to responses follow the request path in the reverse order to get back to
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RELOAD is expected to work under a great number of application RELOAD is expected to work under a great number of application
scenarios. The situations where RELOAD is to be deployed differ scenarios. The situations where RELOAD is to be deployed differ
greatly. For instance, some deployments are global, such as a Skype- greatly. For instance, some deployments are global, such as a Skype-
like system intended to provide public service. Some run in closed like system intended to provide public service. Some run in closed
networks of small scale. SRR works in any situation, but RPR may networks of small scale. SRR works in any situation, but RPR may
work better in some specific scenarios. work better in some specific scenarios.
3.1. Overview 3.1. Overview
RELOAD is a simple request-response protocol. After sending a RELOAD is a simple request-response protocol. After sending a
request, a node waits for a response from a destination node. There request, a peer waits for a response from a destination peer. There
are several ways for the destination node to send a response back to are several ways for the destination peer to send a response back to
the source node. In this section, we will provide detailed the source peer. In this section, we will provide detailed
information on RPR. information on RPR.
Note that the same illustrative settings can be found in DRR draft Note that the same illustrative settings can be found in DRR draft
[I-D.ietf-p2psip-drr]. [I-D.ietf-p2psip-drr].
3.1.1. Relay Peer Routing (RPR) 3.1.1. Relay Peer Routing (RPR)
If peer A knows it is behind a NAT or NATs, and knows one or more If peer A knows it is behind a NAT or NATs, and knows one or more
relay peers with whom they have a prior connections, peer A can try relay peers with whom they have a prior connections, peer A can try
RPR. Assume A is associated with relay peer R. When sending the RPR. Assume A is associated with relay peer R. When sending the
request, peer A includes information describing peer R transport request, peer A includes information describing peer R transport
address in the request. When peer X receives the request, peer X address in the request. When peer X receives the request, peer X
sends the response to peer R, which forwards it directly to Peer A on sends the response to peer R, which forwards it directly to Peer A on
the existing connection. Note that RPR also allows a shorter route the existing connection. Note that RPR also allows a shorter route
for responses compared to SRR, which means less overhead on for responses compared to SRR, which means less overhead on
intermediary peers. Establishing a connection to the relay with TLS intermediary peers. Establishing a connection to the relay with TLS
requires multiple round trips. Please refer to Section 5 for cost requires multiple round trips. Please refer to Section 5 for cost
comparison between SRR and RPR. comparison between SRR and RPR.
This technique relies on the relative population of nodes such as A This technique relies on the relative population of peers such as A
that require relay peers and peers such as R that are capable of that require relay peers and peers such as R that are capable of
serving as a relay peers. It also requires mechanism to enable peers serving as a relay peers. It also requires mechanism to enable peers
to know which nodes can be used as their relays. This mechanism may to know which peers can be used as their relays. This mechanism may
be based on configuration, for example as part of the overlay be based on configuration, for example as part of the overlay
configuration an initial list of relay peers can be supplied. configuration an initial list of relay peers can be supplied.
Another option is in a response to ATTACH request the peer can signal Another option is in a response to ATTACH request the peer can signal
that it can be used as a relay peer. that it can be used as a relay peer.
A B C D X R A B C D X R
| Request | | | | | | Request | | | | |
|----------->| | | | | |----------->| | | | |
| | Request | | | | | | Request | | | |
| |----------->| | | | | |----------->| | | |
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Bootstrap peers must be publicly reachable in a RELOAD architecture. Bootstrap peers must be publicly reachable in a RELOAD architecture.
As a result, one possible architecture would be to use the bootstrap As a result, one possible architecture would be to use the bootstrap
peers as relay peers for use with RPR. The requirements for being a peers as relay peers for use with RPR. The requirements for being a
relay peer are publicly accessible and maintaining a direct relay peer are publicly accessible and maintaining a direct
connection with its client. As such, bootstrap peers are well suited connection with its client. As such, bootstrap peers are well suited
to play the role of relay peers. to play the role of relay peers.
3.2.3. Wireless Scenarios 3.2.3. Wireless Scenarios
While some mobile deployments may use clients, in mobile networks In some mobile deployments, using RPR may help with reducing radio
using peers, RPR may reduce radio battery usage and bandwidth usage battery usage and bandwidth by the intermediary peers. The service
by the intermediary peers. The service provider may recommend in the provider may recommend in the configuration using RPR based on his
configuration using RPR based on his knowledge of the topology. Such knowledge of the topology. Such relay peers may also help
relay peers may also help connectivity to external networks. connectivity to external networks.
4. Relationship Between SRR and RPR 4. Relationship Between SRR and RPR
4.1. How RPR Works 4.1. How RPR Works
Peers using RPR must maintain a connection with their relay peer(s). Peers using RPR must maintain a connection with their relay peer(s).
This can be done in the same way as establishing a neighbor This can be done in the same way as establishing a neighbor
connection between peers by using the Attach method. connection between peers by using the Attach method.
A requirement for RPR is for the source peer to convey their relay A requirement for RPR is for the source peer to convey their relay
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RPR is not intended to replace SRR. As seen from Section 3, RPR has RPR is not intended to replace SRR. As seen from Section 3, RPR has
better performance in some scenarios, but have limitations as well, better performance in some scenarios, but have limitations as well,
see for example section 4.3 in Non-Transitive Connectivity and DHTs see for example section 4.3 in Non-Transitive Connectivity and DHTs
[http://srhea.net/papers/ntr-worlds05.pdf]. As a result, it is [http://srhea.net/papers/ntr-worlds05.pdf]. As a result, it is
better to use these two modes together to adapt to each peer's better to use these two modes together to adapt to each peer's
specific situation. Note that the informative suggestions on how to specific situation. Note that the informative suggestions on how to
transition between SRR and RPR (e.g. compute success rate of RPR, transition between SRR and RPR (e.g. compute success rate of RPR,
fall back to SRR, etc) are same with that on DRR and RPR. Please fall back to SRR, etc) are same with that on DRR and RPR. Please
refer to DRR draft [I-D.ietf-p2psip-drr] for more details. refer to DRR draft [I-D.ietf-p2psip-drr] for more details.
Similarly, the node can decide whether to try RPR based on other Similarly, the peer can decide whether to try RPR based on other
information such as configuration file information. If a relay peer information such as configuration file information. If a relay peer
is provided by the service provider, nodes may prefer RPR over SRR. is provided by the service provider, peers may prefer RPR over SRR.
5. Comparison on cost of SRR and RPR 5. Comparison on cost of SRR and RPR
The major advantages in using RPR are in going through less The major advantages in using RPR are in going through less
intermediary peers on the response. By doing that it reduces the intermediary peers on the response. By doing that it reduces the
load on those peers' resources like processing and communication load on those peers' resources like processing and communication
bandwidth. bandwidth.
5.1. Closed or managed networks 5.1. Closed or managed networks
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OverlayLinkType: refers to the transport type which is used to OverlayLinkType: refers to the transport type which is used to
deliver responses from the destination peer to the relay peer. deliver responses from the destination peer to the relay peer.
IpAddressPort: refers to the transport address that the destination IpAddressPort: refers to the transport address that the destination
peer should use to send the response to. This will be a relay peer peer should use to send the response to. This will be a relay peer
address for RPR. address for RPR.
Destination: refers to the relay peer itself. If the routing mode is Destination: refers to the relay peer itself. If the routing mode is
RPR, then the destination contains two destinations, which are the RPR, then the destination contains two destinations, which are the
relay peer's node-id and the sending node's node-id. relay peer's Node-ID and the sending peer's Node-ID.
6.3. Creating a Request 6.3. Creating a Request
6.3.1. Creating a request for RPR 6.3.1. Creating a request for RPR
When using RPR for a transaction, the sending peer MUST set the When using RPR for a transaction, the sending peer MUST set the
IGNORE-STATE-KEEPING flag in the ForwardingHeader. Additionally, the IGNORE-STATE-KEEPING flag in the ForwardingHeader. Additionally, the
peer MUST construct and include a ForwardingOptions structure in the peer MUST construct and include a ForwardingOptions structure in the
ForwardingHeader. When constructing the ForwardingOption structure, ForwardingHeader. When constructing the ForwardingOption structure,
the fields MUST be set as follows: the fields MUST be set as follows:
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be defined as follows: be defined as follows:
2.1) routemode set to 0x02 (RPR). 2.1) routemode set to 0x02 (RPR).
2.2) transport set as appropriate for the relay peer. 2.2) transport set as appropriate for the relay peer.
2.3) ipaddressport set to the transport address of the relay peer 2.3) ipaddressport set to the transport address of the relay peer
that the sender wishes the message to be relayed through. that the sender wishes the message to be relayed through.
2.4) destination structure MUST contain two values. The first MUST 2.4) destination structure MUST contain two values. The first MUST
be defined as type peer and set with the values for the relay peer. be defined as type node and set with the values for the relay peer.
The second MUST be defined as type peer and set with the sending The second MUST be defined as type node and set with the sending
peer's own values. peer's own values.
6.4. Request And Response Processing 6.4. Request And Response Processing
This section gives normative text for message processing after RPR is This section gives normative text for message processing after RPR is
introduced. Here, we only describe the additional procedures for introduced. Here, we only describe the additional procedures for
supporting RPR. Please refer to [I-D.ietf-p2psip-base] for RELOAD supporting RPR. Please refer to [I-D.ietf-p2psip-base] for RELOAD
base procedures. base procedures.
6.4.1. Destination Peer: Receiving a Request And Sending a Response 6.4.1. Destination Peer: Receiving a Request And Sending a Response
When the destination peer receives a request, it will check the When the destination peer receives a request, it will check the
options in the forwarding header. If the destination peer can not options in the forwarding header. If the destination peer can not
understand extensive_routing_mode option in the request, it MUST understand extensive_routing_mode option in the request, it MUST
attempt to use SRR to return an "Error_Unknown_Extension" response attempt to use SRR to return an "Error_Unknown_Extension" response
(defined in Section 5.3.3.1 and Section 13.9 in [I-D.ietf-p2psip- (defined in Section 6.3.3.1 and Section 14.9 in [I-D.ietf-p2psip-
base]) to the sending peer. base]) to the sending peer.
If the routing mode is RPR, the destination peer MUST construct a If the routing mode is RPR, the destination peer MUST construct a
Destination list for the response with two entries. The first MUST destination_list for the response with two entries. The first MUST
be set to the relay peer node-id from the option in the request and be set to the relay peer Node-ID from the option in the request and
the second MUST be the sending node node-id from the option of the the second MUST be the sending peer Node-ID from the option of the
request. request.
In the event that the routing mode is set to RPR and there are not In the event that the routing mode is set to RPR and there are not
exactly two destinations the destination peer MUST try to send an exactly two destinations the destination peer MUST try to send an
"Error_Unknown_Extension" response (defined in Section 5.3.3.1 and "Error_Unknown_Extension" response (defined in Section 6.3.3.1 and
Section 13.9 in [I-D.ietf-p2psip-base]) to the sending peer using Section 14.9 in [I-D.ietf-p2psip-base]) to the sending peer using
SRR. SRR.
After the peer constructs the destination list for the response, it After the peer constructs the destination_list for the response, it
sends the response to the transport address which is indicated in the sends the response to the transport address which is indicated in the
ipaddressport field in the option using the specific transport mode ipaddressport field in the option using the specific transport mode
in the Forwardingoption. If the destination peer receives a in the Forwardingoption. If the destination peer receives a
retransmit with SRR preference on the message it is trying to retransmit with SRR preference on the message it is trying to
response to now, the responding peer should abort the RPR response response to now, the responding peer should abort the RPR response
and use SRR. and use SRR.
6.4.2. Sending Peer: Receiving a Response 6.4.2. Sending Peer: Receiving a Response
Upon receiving a response, the peer follows the rules in [I-D.ietf- Upon receiving a response, the peer follows the rules in [I-D.ietf-
p2psip-base]. If the sender used RPR and does not get a response p2psip-base]. If the sender used RPR and does not get a response
until the timeout, it MAY either resend the message using RPR but until the timeout, it MAY either resend the message using RPR but
with a different relay peer (if available), or resend the message with a different relay peer (if available), or resend the message
using SRR. using SRR.
6.4.3. Relay Peer Processing 6.4.3. Relay Peer Processing
Relay peers are designed to forward responses to nodes who are not Relay peers are designed to forward responses to peers who are not
publicly reachable. For the routing of the response, this draft publicly reachable. For the routing of the response, this draft
still uses the destination list. The only difference from SRR is still uses the destination_list. The only difference from SRR is
that the destination list is not the reverse of the via-list, instead that the destination_list is not the reverse of the via_list, instead
it is constructed from the forwarding option as described below. it is constructed from the forwarding option as described below.
When a relay peer receives a response, it MUST follow the rules in When a relay peer receives a response, it MUST follow the rules in
[I-D.ietf-p2psip-base]. It receives the response, validates the [I-D.ietf-p2psip-base]. It receives the response, validates the
message, re-adjust the destination-list and forward the response to message, re-adjust the destination_list and forward the response to
the next hop in the destination list based on the connection table. the next hop in the destination_list based on the connection table.
There is no added requirement for relay peer. There is no added requirement for relay peer.
7. Discovery Of Relay Peer 7. Discovery Of Relay Peer
There are several ways to distribute the information about relay There are several ways to distribute the information about relay
peers throughout the overlay. P2P network providers can deploy some peers throughout the overlay. P2P network providers can deploy some
relay peers and advertise them in the configuration file. With the relay peers and advertise them in the configuration file. With the
configuration file at hand, peers can get relay peers to try RPR. configuration file at hand, peers can get relay peers to try RPR.
Another way is to consider relay peer as a service and then some Another way is to consider relay peer as a service and then some
service advertisement and discovery mechanism can also be used for service advertisement and discovery mechanism can also be used for
discovering relay peers, for example, using the same mechanism as discovering relay peers, for example, using the same mechanism as
used in TURN server discovery in base RELOAD [I-D.ietf-p2psip-base]. used in TURN server discovery in base RELOAD [I-D.ietf-p2psip-base].
Another option is to let a peer advertise his capability to be a Another option is to let a peer advertise his capability to be a
relay in the response to ATTACH or JOIN. relay in the response to ATTACH or JOIN.
8. Optional Methods to Investigate Node Connectivity 8. Optional Methods to Investigate Peer Connectivity
This section is for informational purposes only for providing some This section is for informational purposes only for providing some
mechanisms that can be used when the configuration information does mechanisms that can be used when the configuration information does
not specify if RPR can be used. It summarizes some methods which can not specify if RPR can be used. It summarizes some methods which can
be used for a node to determine its own network location compared be used for a peer to determine its own network location compared
with NAT. These methods may help a node to decide which routing mode with NAT. These methods may help a peer to decide which routing mode
it may wish to try. Note that there is no foolproof way to determine it may wish to try. Note that there is no foolproof way to determine
if a node is publically reachable, other than via out- of-band if a peer is publically reachable, other than via out-of-band
mechanisms. As such, peers using these mechanisms may be able to mechanisms. As such, peers using these mechanisms may be able to
optimize traffic, but must be able to fall back to SRR routing if the optimize traffic, but must be able to fall back to SRR routing if the
other routing mechanisms fail. other routing mechanisms fail.
For RPR to function correctly, a node may attempt to determine For RPR to function correctly, a peer may attempt to determine
whether it is publicly reachable. If it is not, RPR may be chosen to whether it is publicly reachable. If it is not, RPR may be chosen to
route the response with the help from relay peers, or the peers route the response with the help from relay peers, or the peers
should fall back to SRR. NATs and firewalls are two major should fall back to SRR. NATs and firewalls are two major
contributors preventing RPR from functioning properly. There are a contributors preventing RPR from functioning properly. There are a
number of techniques by which a node can get its reflexive address on number of techniques by which a peer can get its reflexive address on
the public side of the NAT. After obtaining the reflexive address, a the public side of the NAT. After obtaining the reflexive address, a
peer can perform further tests to learn whether the reflexive address peer can perform further tests to learn whether the reflexive address
is publicly reachable. If the address appears to be publicly is publicly reachable. If the address appears to be publicly
reachable, the nodes to which the address belongs can be a candidate reachable, the peers to which the address belongs can be a candidate
to serve as a relay peer. Nodes which are not publicly reachable may to serve as a relay peer. Peers which are not publicly reachable may
still use RPR to shorten the response path with the help from relay still use RPR to shorten the response path with the help from relay
peers. peers.
Some conditions are unique in P2PSIP architecture which could be Some conditions are unique in P2PSIP architecture which could be
leveraged to facilitate the tests. In P2P overlay network, each node leveraged to facilitate the tests. In P2P overlay network, each peer
only has partial a view of the whole network, and knows of a few only has partial a view of the whole network, and knows of a few
nodes in the overlay. P2P routing algorithms can easily deliver a peers in the overlay. P2P routing algorithms can easily deliver a
request from a sending node to a peer with whom the sending node has request from a sending peer to a peer with whom the sending peer has
no direct connection. This makes it easy for a node to ask other no direct connection. This makes it easy for a peer to ask other
nodes to send unsolicited messages back to the requester. peers to send unsolicited messages back to the requester.
The approaches for a node to get the addresses needed for the further The approaches for a peer to get the addresses needed for the further
tests, as well as the test for learning whether a peer may be tests, as well as the test for learning whether a peer may be
publicly reacheable is same as the DRR case. Please refer to DRR publicly reacheable is same as the DRR case. Please refer to DRR
draft [I-D.ietf-p2psip-drr] for more details. draft [I-D.ietf-p2psip-drr] for more details.
9. Security Considerations 9. Security Considerations
As a routing alternative, the security part of RPR conforms to As a routing alternative, the security part of RPR conforms to
section 12.6 in based draft[I-D.ietf-p2psip-base] which describes section 13.6 in based draft[I-D.ietf-p2psip-base] which describes
routing security. routing security.
10. IANA Considerations 10. IANA Considerations
No IANA action is needed. No IANA action is needed.
11. Acknowledgements 11. Acknowledgements
David Bryan has helped extensively with this document, and helped David Bryan has helped extensively with this document, and helped
provide some of the text, analysis, and ideas contained here. The provide some of the text, analysis, and ideas contained here. The
skipping to change at page 14, line 7 skipping to change at page 14, line 4
11. Acknowledgements 11. Acknowledgements
David Bryan has helped extensively with this document, and helped David Bryan has helped extensively with this document, and helped
provide some of the text, analysis, and ideas contained here. The provide some of the text, analysis, and ideas contained here. The
authors would like to thank Ted Hardie, Narayanan Vidya, Dondeti authors would like to thank Ted Hardie, Narayanan Vidya, Dondeti
Lakshminath, Bruce Lowekamp, Stephane Bryant and Marc Petit-Huguenin Lakshminath, Bruce Lowekamp, Stephane Bryant and Marc Petit-Huguenin
for their constructive comments. for their constructive comments.
12. References 12. References
12.1. Normative References 12.1. Normative References
[I-D.ietf-p2psip-base] Jennings, C., Lowekamp, B., Rescorla, E., [I-D.ietf-p2psip-base] Jennings, C., Lowekamp, B., Rescorla, E.,
Baset, S., and H. Schulzrinne, "REsource LOcation And Discovery Baset, S., and H. Schulzrinne, "REsource LOcation And Discovery
(RELOAD) Base Protocol", draft-ietf-p2psip-base-21 (work in (RELOAD) Base Protocol", draft-ietf-p2psip-base-22 (work in
progress), March 2012. progress), July 2012.
[I-D.ietf-p2psip-concepts] Bryan, D., Matthews, P., Shim, E., Willis, [I-D.ietf-p2psip-concepts] Bryan, D., Matthews, P., Shim, E., Willis,
D., and S. Dawkins, "Concepts and Terminology for Peer to Peer SIP", D., and S. Dawkins, "Concepts and Terminology for Peer to Peer SIP",
draft-ietf-p2psip-concepts-04 (work in progress), October 2011. draft-ietf-p2psip-concepts-04 (work in progress), October 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[I-D.ietf-p2psip-drr] Zong, N., Jiang, X., Even, R. and Zhang, Y., [I-D.ietf-p2psip-drr] Zong, N., Jiang, X., Even, R. and Zhang, Y.,
"An extension to RELOAD to support Direct Response Routing", "An extension to RELOAD to support Direct Response Routing",
draft-ietf-p2psip-drr-02, May 2012. draft-ietf-p2psip-drr-03, October 2012.
12.2. Informative References 12.2. Informative References
[ChurnDHT] Rhea, S., "Handling Churn in a DHT", Proceedings of the [ChurnDHT] Rhea, S., "Handling Churn in a DHT", Proceedings of the
USENIX Annual Technical Conference. Handling Churn in a DHT, June USENIX Annual Technical Conference. Handling Churn in a DHT, June
2004. 2004.
[DTLS] Modadugu, N., Rescorla, E., "The Design and Implementation of [DTLS] Modadugu, N., Rescorla, E., "The Design and Implementation of
Datagram TLS", 11th Network and Distributed System Security Symposium Datagram TLS", 11th Network and Distributed System Security Symposium
(NDSS), 2004. (NDSS), 2004.
[I-D.ietf-behave-nat-behavior-discovery] MacDonald, D. and B. [RFC5780] MacDonald, D. and B. Lowekamp, "NAT Behavior Discovery
Lowekamp, "NAT Behavior Discovery Using STUN", Using STUN", RFC5780, May 2010.
draft-ietf-behave-nat-behavior-discovery-04 (work in progress), July
2008.
[I-D.ietf-behave-tcp] Guha, S., Biswas, K., Ford, B., Sivakumar, S., [I-D.ietf-behave-tcp] Guha, S., Biswas, K., Ford, B., Sivakumar, S.,
and P. Srisuresh, "NAT Behavioral Requirements for TCP", and P. Srisuresh, "NAT Behavioral Requirements for TCP",
draft-ietf-behave-tcp-08 (work in progress), September 2008. draft-ietf-behave-tcp-08 (work in progress), September 2008.
[I-D.lowekamp-mmusic-ice-tcp-framework] Lowekamp, B. and A. Roach, "A [I-D.lowekamp-mmusic-ice-tcp-framework] Lowekamp, B. and A. Roach, "A
Proposal to Define Interactive Connectivity Establishment for the Proposal to Define Interactive Connectivity Establishment for the
Transport Control Protocol (ICE-TCP) as an Extensible Framework", Transport Control Protocol (ICE-TCP) as an Extensible Framework",
draft-lowekamp-mmusic-ice-tcp-framework-00 (work in progress), draft-lowekamp-mmusic-ice-tcp-framework-00 (work in progress),
October 2008. October 2008.
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