PPSP Group G.Lu
Internet Draft JC.Zuniga
Intended status: Informational A.Rahman
Expires: September 1, 2010 InterDigital Communications, LLC
March 1, 2010
P2P Streaming for Mobile Nodes: Scenarios and Related Issues
draft-lu-ppsp-mobile-00.txt
Abstract
The scenarios where a Peer-to-Peer Streaming Protocol (PPSP) contains
mobile nodes need special considerations. An analysis of all the
scenarios that involve mobile nodes is necessary to provide the
guidelines to PPSP protocol design and applicability. This document
describes the major scenarios for a PPSP network with mobile nodes
and identifies some of the key issues.
Status of this Memo
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This Internet-Draft will expire on September 1, 2010.
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Copyright Notice
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Table of Contents
1. Introduction...................................................2
2. Conventions and Terminology....................................3
3. Link Layer Mobility............................................3
4. IP Mobility....................................................4
4.1. Simple IP.................................................4
4.2. Mobile IP.................................................5
4.3. Proxy Mobile IP...........................................6
5. Mobility support with RELOAD...................................6
6. Tracker Mobility...............................................7
7. Geo-Targeting Issues...........................................7
8. Mobile Node Capabilities.......................................8
8.1. Multiple Interfaces.......................................8
8.2. Uplink vs. Downlink Bandwidth.............................8
8.3. Processing Power..........................................8
9. Security Considerations........................................8
10. IANA Considerations...........................................8
11. References....................................................8
11.1. Normative References.....................................8
11.2. Informative References...................................9
12. Acknowledgments...............................................9
1. Introduction
In the past P2P solutions have mostly targeted wired or fixed
connections. Mobile P2P communications are expected to grow rapidly
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and the nature of mobile nodes and mobile environments cause specific
challenges to P2P communications, specifically for streaming
scenarios. This draft discusses such mobility specific issues with
the illustration of different scenarios.
2. Conventions and Terminology
This document uses the same terminologies as [I-D.zhang-ppsp-problem-
statement]. For simplicity, this document illustrates scenarios
showing a centralized Tracker architecture. However, it should be
understood that all the scenarios also apply to the distributed
architecture, e.g. using a Distributed Hash Table (DHT).
3. Link Layer Mobility
PPSP uses a P2P based overlay network on top of the transport
network. Mobility or link quality at link layers is not visible to
the peers. A Peer-To-Peer streaming session quality can suffer from
high error rate and low throughput due to poor link layer conditions
seen in mobile networks. Frame loss, audio/video synch loss, or
streaming stalls are likely to be seen and ultimately Peer-to-Peer
Streaming session can be terminated abruptly as a result of changes
in L2 connectivity. Such scenario is illustrated in Figure 1.
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P2P streaming network
+---------+
---------- >| Tracker |< ----------
| +---------+ |
| |
| |
| |
| 2)P2P streaming session |
V quality is poor or terminated V
+------+ +------+
|Peer 1|< ------------X------------ >|Peer 2|
+------+ +------+
IP1 ^ ^ IP2
| |
X 1) Peer 1 lost |
| connection |
v v
****** ******
* NW1 * * NW2 *
* * * *
****** ******
Figure 1 P2P Streaming with Link Layer Mobility
4. IP Mobility
4.1. Simple IP
Simple IP refers to the scenario where there is no mobile IP or Proxy
Mobile IP, and a peer needs to obtain a new IP address through a
standard method like DHCP after losing the previous IP address.
As illustrated in Figure 2, when peer 1 moves from NW1 to NW1', its
IP address changes from IP1 to IP1'. The P2P Streaming session
between peer 1 and peer 2 may degrade or completely be lost.
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P2P streaming network
+---------+
---------- >| Tracker |< ----------
| +---------+ |
| |
| |
| |
| |
V V
+------+ +------+
|Peer 1|< ------------------------- >|Peer 2|
+------+ +------+
IP1 ^ ^ IP1' ^ IP2
| | |
X ------- |
| | |
v v v
****** ****** ******
* NW1 * * NW1' * * NW2 *
* * * * * *
****** ****** ******
Figure 2 P2P Streaming with Simple IP
4.2. Mobile IP
Mobile IP provides IP mobility and hides the mobile's movement from
the Correspondent Node (CN).
Figure 3 illustrates the case when peer 1 moves from NW1 to NW1'.
Because of Mobile IP, neither the tracker nor peer 2 are aware of the
change of network for peer 1. This may cause quality problems for the
P2P Streaming session. For example, peer 1 may experience high
latency and increased load, which adversely affects the user
experience of the P2P streaming session(s) and may result in
unacceptable performance.
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P2P streaming network
+---------+
---------- >| Tracker |< ----------
| +---------+ |
| |
| |
| |
MIP | IP1 |
Client | P2P Streaming session |
V performance may not be optimal V
+------+ +------+
|Peer 1|< ------------------------- >|Peer 2|
+------+ +------+
^ ^ ^ IP2
| | |
X ------- |
| | |
v v v
****** ****** ******
* NW1 * * NW1' * * NW2 *
* * * * * *
****** ****** ******
Figure 3 P2P Streaming with Mobile IP
4.3. Proxy Mobile IP
The use of Proxy Mobile IP causes similar issues as the ones
mentioned for Mobile IP in the above section. On top of these, Proxy
Mobile IP also introduces a new issue for P2P streaming sessions.
Since Proxy Mobile IP is a network based solution, the mobile node
(peer) is not aware of its IP mobility so it cannot inform the
tracker, P2P Cache, CDNs or other peers of the IP level mobility.
Therefore IP mobility is totally invisible to the P2P Streaming
session entities and harder to detect and respond accordingly.
5. Mobility support with RELOAD
It has already been identified in the proposed WG charter that any
PPSP developed protocol should be analyzed for interactions with the
RELOAD protocol [I-D.ietf-p2psip-base]. The RELOAD protocol provides
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a signaling and routing mechanism for P2P overlay networks over the
general Internet. The latest RELOAD draft
(http://tools.ietf.org/html/draft-ietf-p2psip-base-07) also has a
future consideration section for support of HIP (section 5.6.1.1).
HIP is an experimental mobility protocol with good security
properties.
In addition to HIP, the following mobility protocols should also be
considered for PPSP-RELOAD interactions:
. Mobile IP
. Proxy Mobile IP
6. Tracker Mobility
Normally trackers are assumed to be fixed nodes. However, in a mobile
environment mobile nodes can also become trackers. In this sense,
similar considerations to the ones described above for mobile peers
should be applied to mobile trackers.
7. Geo-Targeting Issues
Geo-targeting is a technique used to determine the physical location
(i.e. geo-location) of a user. The geo-location is based on
geographical and other personal information provided by the requester
peer or a third party. Techniques to determine geo-location of a user
can rely on civic location, GPS geographical coordinates or most
commonly IP address. The primary source for IP address geographical
data is the regional Internet registries.
Depending on the location, different regulations and rules may apply.
For instance, some content may not be distributed on certain
locations or can only be distributed on some other locations.
Current content distribution policies can apply certain rules to P2P
Streaming clients. However, IP mobility can hide a peer or a tracker
moving from one region to another where possibly different content
distribution rules may apply hence rendering the set forth policies
un-enforceable.
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8. Mobile Node Capabilities
Mobile nodes are constrained by nature due to their limited battery,
screen size, computational capability and they operate in variable
and unpredictable environments. These attributes bring about the
problems mentioned above that may adversely affect the P2P Streaming
sessions.
8.1. Multiple Interfaces
A mobile node can switch between different radio access technologies
such as 3G or Wi-Fi occasionally or frequently, which may cause the
P2P Streaming session quality to degrade due to latency introduced or
P2P Streaming session totally terminated.
8.2. Uplink vs. Downlink Bandwidth
Often mobile devices have asymmetrical bandwidth capabilities. For
instance, most mobile devices are capable of handling higher bit
rates in the downlink than in the uplink. Since peer-to-peer
streaming sessions can be either generated or terminated on a mobile
device, these mobile node capabilities should be taken into account.
8.3. Processing Power
Some devices are more capable than others in terms of computational
performance or processing power. Similarly, devices can have
different performance for generating a session (e.g. video recording)
or terminating it (e.g. video display). Taking these differences into
account is important for maintaining a good quality of the P2P
streaming session.
9. Security Considerations
This draft does not introduce new threats to security.
10. IANA Considerations
This document makes no request of IANA.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC2234] Crocker, D. and Overell, P.(Editors), "Augmented BNF for
Syntax Specifications: ABNF", RFC 2234, Internet Mail
Consortium and Demon Internet Ltd., November 1997.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in Ipv6", RFC 3775, June 2004.
11.2. Informative References
[I-D.zhang-ppsp-problem-statement]
Zhang, Y., Zong, N., Camarillo, G., Seng, J., and R. Yang,
"Problem Statement of P2P Streaming Protocol (PPSP)",
draft-zhang-ppsp-problem-statement-05 (Work in progress),
October 20, 2009.
[I-D.zong-ppsp-reqs]
Zong, N., Zhang, Y., Pascual, V., and C. Williams, "P2P
Streaming Protocol (PPSP) Requirements", draft-zong-ppsp-
reqs-02 (Work in progress), October 22, 2009.
[I-D.gu-ppsp-survey]
Gu, Y., Zong, N., Zhang, Hui., Zhang, Y., Camarillo, G.,
and Y. Liu, "Survey of P2P Streaming Applications", draft-
gu-ppsp-survey-01 (Work in progress), October 22, 2009.
[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-07 (Work in progress),
February 17, 2010.
12. Acknowledgments
The authors would like to thank Serhad Doken for his thorough review
and valuable inputs to this draft.
This document was prepared using 2-Word-v2.0.template.dot.
Authors' Addresses
Guang Lu
InterDigital Communications, LLC
Email: Guang.Lu@InterDigital.com
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Juan Carlos Zuniga
InterDigital Communications, LLC
Email: JuanCarlos.Zuniga@InterDigital.com
Akbar Rahman
InterDigital Communications, LLC
Email: Akbar.Rahman@InterDigital.com
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