1 PLuSH – Mesh Tree Fast and Robust Wide-Area Remote Execution Mikhail Afanasyev ‧ Jose Garcia ‧ Brian Lum

2 Introduction PlanetLab is an open platform for developing, deploying and accessing planetary-scale services It allows remote execution on nodes around the world Extremely useful in developing new network technologies Introduction ‧ Mesh Tree ‧ Additional

3 PlanetLab Current distribution of 534 nodes over 253 sites Introduction ‧ Mesh Tree ‧ Additional

4 The Motivation Performance is abysmal Currently, the user must make an SSH connection to each node As the number of nodes grows, the overhead of establishing SSH connections becomes more significant Not all nodes can reach one another directly Introduction ‧ Mesh Tree ‧ Additional

5 The Motivation Flaky Control Controlling large sets of remote processes is difficult Example: C-c will result in remote processes being killed or straggler processors to remain Introduction ‧ Mesh Tree ‧ Additional

6 PLuSH Suppose that someone wants to test a new network application and decides to run the code on 100 machines First, we must be able to determine a list of target nodes to run the experience. Nodes can be picked depending on factors including CPU load, bandwidth, latency, etc. Next, the code must be deployed The code must be started simultaneously on all machines. Once the code is running, we must be able monitor the progress and collect statistics Introduction ‧ Mesh Tree ‧ Additional

7 PLuSH One of the core parts of Plush is the Mesh interface Mesh abstracts the underlying overlay Mesh uses a rough list of hosts to construct an overlay communication mesh by using the host directory to query host names and authentication information. Introduction ‧ Mesh Tree ‧ Additional

8 Weaving the Mesh 1. SSH authentication forwarding 2. Building the tree 3. Adding robustness Mesh Tree: SSH Forwarding ‧ Building the Tree ‧ Robustness

9 How SSH Works Agent listens on “ agent socket ” which is a Unix domain socket. Agent has private key. SSH (on agent ’ s side) makes a connection from Home PC to SSHd (daemon) on PL1, who has the public key. SSHd sends challenge to SSH. SSH connects to Agent socket, gives challenge to Agent. Agent uses private key to make response and forwards to SSH, who forwards to SSHd. Challenge Response Challenge Response public key Mesh Tree: SSH Forwarding ‧ Building the Tree ‧ Robustness

10 Our World with PlanetLab The slice breaks up PL1, so SSH cannot forward to SSHd Challenge Response Challenge Response public key Challenge public key Mesh Tree: SSH Forwarding ‧ Building the Tree ‧ Robustness

11 Response SSH Mesh: Response SSH Mesh: Challenge Our Solution Challenge Response Challenge Response public key Challenge public key Challenge Response Client ’ s STDIN and STDOUT are connected to SSHd Mesh Tree: SSH Forwarding ‧ Building the Tree ‧ Robustness

12 Building the Tree There is rudimentary support for a tree We implemented multiple tree-building algorithms Trees can be built using SSH tree and Macedon Mesh Tree: SSH Forwarding ‧ Building the Tree ‧ Robustness

13 Macedon vs. SSH Mesh Macedon Advantages Support for many protocols Does not spend time decrypting and encrypting Disadvantages Can be easily hijacked Heavy program SSH Mesh Advantages Requires minimum client software Provides protection against both sniffing and hijacking Disadvantages Spends time decrypting and encrypting Mesh Tree: SSH Forwarding ‧ Building the Tree ‧ Robustness

14 Adding Robustness The Forwarding mechanism Forwards SSH connection Allows us to change root so that we can detach the experiment controller Allows us to recover from failures in the root Mesh Tree: SSH Forwarding ‧ Building the Tree ‧ Robustness

15 Comparing the trees Introduction ‧ Mesh Tree ‧ Additional

16 Additional Tools Debugging Tool Deploys required files to all necessary nodes Opens multiple simultaneous connections for very high speeds Stops runaway processes Macedon Testing Tool Shows raw data for underlying Macedon communication networks Controls Macedon networks from console Uses self-developed Perl Macedon bindings Introduction ‧ Mesh Tree ‧ Additional

17 Future Research Work Comparison between more Mesh overlay algorithms Evaluate the performance difference between SSH Mesh and Macedon Introduction ‧ Mesh Tree ‧ Additional

18 Additional Thanks We would like to thank the following people for their help Chris Tuttle Jeannie Albrecht Chip Killian Introduction ‧ Mesh Tree ‧ Additional

19 Conclusion Remote execution in PlanetLab through basic SSH connections is neither scalable nor robust We have implemented a solution that improves both scalability and robustness SSH forwarding mechanism Building the tree Adding robustness Introduction ‧ Mesh Tree ‧ Additional