P2PSIP Working Group Lifeng. Le Internet Draft Intended status: Informational China Mobile Expires: January 2010 July 6, 2009 Hierarchical P2PSIP Overlay draft-le-p2psip-hierachical-p2psip-overlay-00.txt 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), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on January 6, . Copyright Notice Copyright (c) 2009 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Le Expires January 6, 2010 [Page 1] Internet-Draft Hierarchical P2PSIP Overlay July 2009 Abstract This draft discusses the hierarchical overlay architecture in Peer- to-Peer (P2P) SIP system. The P2P SIP is defined as a distributed network and each peer is equal in it. But actually peers are different from each other on many aspects, e.g., physical performance, network performance or system performance (e.g., uptime). So node heterogeneity should been considered enough in P2P SIP system, which affects the scalability and service availability of P2P SIP overlays. This draft introduces the performance concerns of P2P SIP overlay without consideration of node heterogeneity at first. After that, an alternative architecture of hierarchical P2P SIP overlay is brought up. [Page 2] Internet-Draft Hierarchical P2PSIP Overlay July 2009 Table of Contents 1. Introduction................................................4 2. Problem statement...........................................5 3. Hierarchical P2P SIP Architecture............................6 4. Architecture example of hierarchical overlay.................7 5. Benefits of Hierarchical P2PSIP system.......................8 5.1. Virtual storage.........................................8 5.2. Collaborative Processing................................8 6. Use case of Hierarchical P2P SIP.............................9 7. Concerns for Hierarchical P2P SIP system....................10 8. IANA Considerations........................................11 9. Conclusions................................................12 10. References................................................13 10.1. Normative References..................................13 10.2. Informative References................................13 [Page 3] Internet-Draft Hierarchical P2PSIP Overlay July 2009 1. Introduction This draft discusses the significance of considering node heterogeneity in P2P SIP system. Peer capabilities should be exploited sufficiently in order to improve the performance of P2P SIP overlay network. Peers with high performance should contribute more to overlay than peers with low performance. This draft proposes an hierarchical P2P SIP architecture which may be a possible way to make good use of overlay resources. [Page 4] Internet-Draft Hierarchical P2PSIP Overlay July 2009 2. Problem statement In current P2P SIP system, node heterogeneity has not been considered enough, which would affect the scalability and service availability of P2P SIP overlay. Node heterogeneity can be defined from several aspects. From the aspect of physical resources, node heterogeneity can be measured by physical capabilities, such as CPU power, storage capacity (memory or disk); from the aspect of network resources, node heterogeneity can be measured by network capabilities, such as bandwidth or public IP address; from the aspect of system availability, node heterogeneity can be measured by system capabilities, such as online availability or fault tolerance in P2P SIP overlay. Physical and network capabilities may affect the scalability of P2P overlays. In real Internet world, the difference between nodes may have more than three orders of magnitude. So in one overlay, nodes with poor performance may become the bottleneck of system performance. Besides, system capabilities affect service availability of P2P SIP overlay. Stable nodes have long uptime and good fault tolerance in system, so its services can be used by other nodes frequently. In general, the performance of P2P SIP overlay is generally limited by the number of nodes with poor physical, network capabilities and system capabilities (enlightened by the famous Barrel Theory). However, current P2P SIP systems have considered one-level super-node overlay at most which can not still explore the available resources of nodes adequately. So the design goal of P2P SIP system should classify heterogeneous nodes into more than two levels according to their physical capabilities, network capabilities and system capabilities. [Page 5] Internet-Draft Hierarchical P2PSIP Overlay July 2009 3. Hierarchical P2P SIP Architecture According to physical capabilities network capabilities and system capabilities, we can divide an overlay into k suboverlays by different classification algorithms (open issue). In Figure 1, the first suboverlay is the top one that holds the most powerful and stable nodes; the kth suboverlay is the foot one that holds the weakest and most dynamic nodes. If a new node starts up in the hierarchical P2P SIP system, it will obtain a node key by the consistent hash function (e.g., SHA-1) and insert itself into the kth suboverlay originally (new node with zero online time). If it detects enough free capabilities (e.g., enough physical resources, enough bandwidth and enough uptime) to be a member of the (k-)th suboverlay, it will transfer to the upper suboverlay. But if a node has little additional free capabilities even if it has a large capabilities, it can only join the suboverlay in lower level. If an old node starts up, it will directly join the last suboverlay according to history record. Besides, some Incentive mechanisms should be given in hierarchical P2P overlay to encourage nodes to contribute own resources to overlay. +------------------------------------------------+ | |---------------| | | | suboverlay-1 |--Users | | |---|------|----| | | | | | | |-----|------|------| | | | suboverlay-2 |--Users | | |--|------------|---| | | | | | | |-----|------------|------| | | | suboverlay-3 |--Users | | |--|-------------------|--| | | | : | | | : | | | : | | | |-----|-------------------|------| | | | suboverlay-k |--Users| | |--------------------------------| | +------------------------------------------------+ Figure 1 Hierarchical P2PSIP system [Page 6] Internet-Draft Hierarchical P2PSIP Overlay July 2009 4. Architecture example of hierarchical overlay In hierarchical overlay, the neighbored suboverlays should have certain relationship (open issue) in order to form a whole overlay. Here take an example of Chord to illustrate the relationship. In hierarchical overlay, a node in the ith suboverlay can keep connections with nodes in the (i+1)th suboverlay whose keys fall into the key interval governed by nodes in the ith suboverlay. For example showed in Figure 2, N1-48 keeps the connections with N2-32 and N2-47; similarly, N2-32 keeps the connections with N3-24 and N3- 30. N1-48 and N2-47 are called One-hop Father Node and Son Nodes; similarly, N1-48 and N3-46 are called two-hop Father Node and Son Nodes. +----------------------------|--------------|------------------+ |(suboverlay-1) N1-1| N1-21| N1-48| | | | | | : | | | |(suboverlay-2) N2-52| N2-11 | N2-32| N2-47| | | | | | | | | | | |(suboverlay-3) N3-48 N3-51|N3-7 N3-10|N3-24 N3-30|N3-40 N3-46| +---------------------------|----------|-----------|-----------+ Figure 2 The relationship between suboverlays in Hierarchical P2PSIP system [Page 7] Internet-Draft Hierarchical P2PSIP Overlay July 2009 5. Benefits of Hierarchical P2PSIP system 5.1. Virtual storage Virtual storage implies that a node can share the storage capacity of its Father nodes. For example showed in Figure 3, a node, e.g.,N3-46, can store or backup information, e.g., user records or offline messages, in its Father Nodes, e.g.,N1-48 or N2-47, for load balancing or backup. But for the outside nodes, they only know the false fact that the information is stored in N3-46. +------------------------------------------------------------------+ | |--------------| | | | N1-48 <--|--Information is here! | | | | | | | N2-47 | | | | | | | | N3-46 | | | |--------------|<--Information is pushed to N3-46 for storage | +------------------------------------------------------------------+ Figure 3 Virtual storage in Hierarchical P2PSIP system 5.2. Collaborative Processing Collaborative processing implies that a node can process tasks with the help of its Father nodes. Take an example of node location in Figure 4, the source node can send lookup request to its Father nodes to parallel locate the destination node in all suboverlays. Benefiting from collaborative processing between suboverlays, the delay for node location can be reduced largely less than O(logN). +--------------------------------------------------------------+ | |--------------| | | | N1-48 -----> Lookup in suboverlay-1 | | | | | | | N2-47 -----> Lookup in suboverlay-2 | | | | | | | N3-46 -----> Lookup in suboverlay-3 | | |--------|-----| | | | | | +---Node location is initiated in N3-46 | +--------------------------------------------------------------+ Figure 4 Collaborative Processing in Hierarchical P2PSIP system [Page 8] Internet-Draft Hierarchical P2PSIP Overlay July 2009 6. Use case of Hierarchical P2P SIP The hierarchical P2P SIP can be used to P2P content delivery system as shown in Figure 5. Content server divides a content file into content segments and push different segments to different nodes in suboverlay-1 for local cache first; nodes in suboverlay-1 push different segments to its different Son nodes in suboverlay-2; similarly, nodes in suboverlay-(k-1) push different segments to its different Son nodes in suboverlay-k. As a result, content segments can be shared in each suboverlay; the content file can be restored from segments distributed in each suboverlay; nodes in higher-level suboverlays cache and distribute more segments, and vice versa. In Figure 5, UE is more related to the equipment with rare resources, such as mobile UE. UE can select a fixed node in suboverlay as its proxy according to location Proximity. | |--------------| | | |Content Server| | | |-----|--------| | +----------------------|-------------------------+ | |------|--------| | | UE--| suboverlay-1 |--UE | | |---|------|----| | | | | | | |-----|------|------| | | UE--| suboverlay-2 |--UE | | |--|------------|---| | | | | | | | : | | | | : | | | |-----|-------------------|------| | | UE--| suboverlay-k |--UE | | |--------------------------------| | +------------------------------------------------+ Figure 5 P2P Content system based on Hierarchical architecture [Page 9] Internet-Draft Hierarchical P2PSIP Overlay July 2009 7. Concerns for Hierarchical P2P SIP system The number of suboverlays k should be chosen properly. k can not be increased unboundedly because its increase may incur the increase of the maintenance overhead between suboverlays. [Page 10] Internet-Draft Hierarchical P2PSIP Overlay July 2009 8. IANA Considerations There are no IANA considerations associated to this memo. [Page 11] Internet-Draft Hierarchical P2PSIP Overlay July 2009 9. Conclusions This memo introduces the consideration of node heterogeneity. After that, an alternative architecture of hierarchical P2P SIP overlay is brought up. [Page 12] Internet-Draft Hierarchical P2PSIP Overlay July 2009 10. References 10.1. Normative References 10.2. Informative References Author's Addresses Lifeng Le China Mobile Unit 2, 28 Xuanwumenxi Ave, Xuanwu District, Beijing 100053, China Email: Lelifeng@chinamobile.com [Page 13]