Hierarchical Geometric Overlay Multicast Network

In this poster proposal, we presentBos: a hierarchical geometric overlay multicast network that is built on a 2-tier hierarchical architecture called Lightweight SuperPeer Topologies (LST) [1], [2]. Bos makes use of the geometric connectivity and Minimum Spanning Trees (MST) properties of the LST overlay network to provide efficient overlay multicast. We evaluate Bos’s performance using the large-scale network models that were used in Scribe [3] and SplitStream [4]. The results show that Bos performs reasonably well in large size networks with reasonable link and node stress. I. THE LST OVERLAY NETWORK The construction of2-tier hierarchical architecture of LST overlay network consists of three key steps:Step 1: SuperPeer election.When a new overlay node joins the LST overlay network, the following criteria are evaluated to determine whether this overlay node will be elected as a SuperPeer or normal Peer: A) The SuperPeer should have enoughresources to serve other SuperPeers and peers. B) The SuperPeer should bereliable or stableand it is not joining and leaving the LST overlay network very frequently. With the above criteria imposed, the SuperPeers layer will consist o f SuperPeers acting as backbone high-speed gateway for the peers in the peers layer. The list of SuperPeers are being classified as the list of landmark nodes (lighthouses) for th e procedure in Step2. Step 2: Highways [5]. Highways is an overlay network control plane service [5] that performs scalable network embedding [6] to map overlay nodes in metric space onto geometric points in geometric space and assign geometric coordinates to the overlay nodes to repres nt their geometric position for the construction of the geomet ric overlay network. If accurate, such techniques would allow u s to predict Internet distances without extensive measureme nts. We use landmark-based and Singular Value Decomposition (SVD) embedding techniques for low-dimensional network embedding. Firstly, Round-Trip-Time’s (RTT’s) measureme nts of each overlay node to at least d + 1 landmark nodes (SuperPeers) are performed for embedding into d-dimensional geometric space. Network superspace embedding embeds the whole set of overlay nodes in the system as one large set into Global geometric space while subspace embedding embeds all small partitioned clusters of overlay nodes into Local geometric space. The rationale for performing network subspace embedding arises from the scalability (meta-) met ric observations in [6], subspace embeddings into Euclidean sp ce of various partitioned clusters of overlay nodes achieve better accuracy in geometric distance estimation. Using the overl ay nodes’ Global geometric position information, all overlay nodes in the overlay network are partitioned into clusters by adopting a simplistic approach of the K-means method (we useK = 3). Network subspace embedding is done to overlay nodes within these clusters. Therefore, all overla y nodes will have bothGlobal and Local geometric position information. The local geometric position information hel ps to provide a more accurate geometric distance estimation among overlay nodes in the cluster while the global geometri c position estimates the geometric distances between overla y nodes in different clusters. We recognize the fact that slim possibility of inaccuracy in overlay nodes’ rank ordering thro ugh geometric distance estimation may happen. In order to mitig ate this, from the perspective of each node, a sanitary check is done for the list ofclosestg = 10 nodes derived from its geometric distances. That is, a comparison is performed wit h its measured RTTs and re-ordering of the list of closestnodes is done if distance ordering errors were found. This sanitar y check helps in ensuring the list of closestnodes is identified. Step 3: SuperPeers and Peers Topology Construction. In the SuperPeers layer, we use Yao-Graphs[7] to construct the ov rlay network connectivity among the SuperPeers by using their geometric position information and estimated geomet ric distances with other SuperPeers as computed from Step 2. Since the geometric space around the SuperPeer is cut into six sectors of equal angleθ < π/3), every SuperPeer choose thesix closestSuperPeers in terms of their geometric distances to connect to. These SuperPeer-SuperPeer YaoGraphs routesserve as the reliable high-bandwidth backbone network connectivity. In the Peers layer, Peers are directl y connected to the first closestSuperPeers that are capable of serving an additional Peer and this connectivity is called t he Peer-SuperPeer 1-Hop route. Among the Peers being served by their closest SuperPeer, direct connectivity between th se Peers can be established if there exists a shortcut route bet w en the Peers. That is, a Peer-Peer Shortcut routeis established between two Peers belonging to a SuperPeer, if the direct connectivity between these two Peers is the shortest route compared to their Peer-SuperPeer 1-Hop routes.