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VTL: A Transparent Network Service Framework
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  1. VTL: A Transparent Network Service Framework John R. Lange and Peter A. Dinda Prescience Lab Department of Electrical Engineering and Computer Science Northwestern University http://plab.cs.northwestern.edu

  2. Transparent Network Services • Manipulate data and signaling of flows/connections to add services to existing unmodified applications and OSes • High Level transformations of Low Level traffic • Transparency: Manipulations invisible to guest environment • VTL (Virtual Traffic Layer) • A framework for creating Transparent Network Services • Wide range of possible services • Many useful for HPDC

  3. Outline • Defining Transparent Network Services • Motivation • VTL Framework • Architecture • Performance • Example Transparent Network Services • Protocol Transformations • Anonymous Networking • … • Conclusion and Future Work

  4. Transparency • Improving Existing Unmodified Applications • Invisible to connection end points • No changes to guest environment • Seamless integration of networking techniques • Transparency readily available with VMS • Provide transparent bridge • Service integration below virtual hardware

  5. Network Services • Implement high level functions • Operate on low level network traffic • Monitor • Control • Manipulate • Traffic Data • Signaling • Unique challenges in Virtual Environments • E.g. Migration

  6. Motivation • HPDC 2005 -- VRESERVE • Automatic Optical Network Reservations for unmodified applications • Demonstrated performance gains over standard internet routes • Performance Issues • TCP applications ill suited for optical networks J. Lange, A. Sundararaj, and P. Dinda, Automatic Dynamic Run-time Optical Network Reservations, Proceedings of the 14th IEEE International Symposium on High Performance Distributed Computing, (HPDC 2005)

  7. TCP over Optical Networks • Optical Networks have high BDPs • Bandwidth Delay Products • Very High bandwidth • Long distance • High relative latency • TCP breaks down D. Petravick, Fermilab

  8. Typical BDP values • Assume endpoints are on opposite ends of the earth • Real world example: CERN and StarLight • Latency lower bound is ~60ms • Half circumference of earth / Speed of light • CERN <–> FNAL has a measured ~60 ms delay • D. Petravick, Fermilab • Optical Networks currently operate at 10 Gbps • But 1 GigE NICs are most common • TCP Window Size (BDP): • 10 Gbps ~= 70 MB • 1 Gbps ~= 7MB • SACK lookups cause TCP timeouts • Window size  1

  9. Transparently Optimize high BDP flows • High performance protocols exist • UDT/SABUL, RBUDP, etc… • But applications must be configured for them • Need method of transforming TCP to UDT • Opens UDT connections based on SYNs • Transmits data segments over UDT

  10. VTL • Transparent Network Service Framework • Network device interface • Packet modification and creation • Rapid prototyping and evaluation • Capabilities • Virtual TCP endpoint • Transparent packet generator • Acks, keep-alive • Packet header and content modifications • Not confined to virtual machines

  11. VTL Components • Network Interface API • Reads/Writes packets to/from network interfaces • Packet Access API • Reading and writing packet data • State Models • Maintain state of connection endpoints

  12. Network Interface API • Common interface for packet capture and injection • Virtual or Real devices • Unix or Windows • Built on PCAP and libnet • Operations • Connect/Disconnect • Read/Write • Packet notifications

  13. Packet Access API • Packet inspection and modification • Primitives to access standard fields • Higher level functions built on primitives • Packet class queries • Field swapping • Header calculations • Derivative packet creation

  14. Connection State Models • Maintain and manipulate protocol state • Layered architecture • Create packets belonging to a connection • State kept for both connection endpoints • Generate packets from either endpoint • API operation • Manual or packet based • Model Initialization • State Updates • Packet Creation

  15. VTL Configuration Hosting Server (Windows or Unix) VM VMM (VMWare, Xen, etc) Host-only interface VNET Overlay Module UDT Flow Over Optical Network VTL VNET Physical interface Sundararaj, A., Gupta, A., , and Dinda, P. Increasing application performance in virtual environments through run-time inference and adaptation. In Proc. of the 14th IEEE International Symposium on High Performance Distributed Computing (HPDC) (July 2005)

  16. Baseline Performance • Limited by Network Interface API • Implemented in user space • PCAP + libnet • Experimental setup • Simple interface bridge (virtual->real) • Xen bridge • Single process (half duplex) • Two processes (full duplex)

  17. Baseline Performance Overhead Measurements Bandwidth (MB/s) Xen Bridge One VTL Process Two VTL Processes

  18. Protocol Transformation for High BDP networks • Addresses performance of TCP over optical • VTL allows transformation of TCP flows to other transport protocols • VTL module acts as virtual TCP endpoint • Implements TCP states • SYN sequence (open) • FIN sequence (close) • Data Transfer over new protocol (established)

  19. Code Example – Creating Packets int create_data_pkt(vtl_model_t * model, char * data, int data_len) { RawEthernetPacket data_pkt; create_empty_pkt(model, &data_pkt, INBOUND_PKT); memcpy(TCP_DATA(data_pkt), data, data_len); compute_ip_len(&data_pkt, data_len); compute_ip_checksum(&data_pkt); compute_tcp_checksum(&data_pkt); sync_model(model, &data_pkt); queue_pkt(&data_pkt); }

  20. Performance Evaluation Setup • Comparing TCP vs. VTL + UDT • Added artificial latency to gigabit switch • Linux iproute2 + tc netem • TTCP benchmark • Standard TCP (Host to host) • TCP with intelligent socket buffers (Host to host) • VTL + UDT (Xen VM to Xen VM) • Note: No virtualization present for TCP tests • Same hardware

  21. Performance Bandwidth (MB/s) Latency (ms)

  22. More Transparent Network Services • Socks (TOR) • Subnet Tunneling • VM Migration Support (TCP keep alive) • Stateful Firewall • Performance Enhancing Proxies • RFC 3135 • Local acknowledgements

  23. Anonymous Networking for Any Application • Tor Anonymous Network (http://tor.eff.org) • Anonymizes source of any TCP connection • Functions as a SOCKS proxy • Requires SOCKS application support VM Tor Server VMM (VMWare, Xen, etc) TOR NETWORK SOCKS Connection VTL Host-only interface TCP Connections + DNS lookups VTL Interface Hosting Service

  24. Tor + VTL • VTL implements transparent SOCKS interface • VTL simulates a TCP endpoint • Extracts data segment from TCP packet and transmits it over SOCKS tunnel • Data from SOCKS is encapsulated into TCP packets and delivered to VM • Gotchas • DNS is UDP based • VTL handles DNS case for UDP • ARPs • VTL answers ARPs with a fake MAC address • All tcp connections from a VM are anonymized • No modification to OS or applications • User not restricted to applications implementing socks

  25. Transparent Security • Iptables and Windows Firewall are now ubiquitous • Not perfect • Successful attacker can alter rules • Only as strong as the weakest link • VTL rules are not accessible by VM • Even if VM is compromised firewall rules are safe

  26. Subnet Tunneling VNET Proxy (PROXY1) Gateway (GW1) VM1 LAN connection Internet VNET Overlay (Internet) Gateway Router MAC Address Mismatch! VM2 Gateway (GW2) VNET Proxy (PROXY2)

  27. Subnet Tunneling • Two VMs on different subnets communicating • Fast Path link is available between them • Bypasses routers • VMs use subnet gateway • Set gateway MAC as destination • VTL rewrites destination MAC addresses • Route packets on fast path link

  28. Network Suspension during VM Migrations • A VM is suspended for a long duration • i.e. VM is migrating over WAN • Open TCP connections begin to timeout • In order to maintain connections VTL generates keep-alive packets • Secondary service must handle routing • i.e. VNET

  29. Cooperative Selective Wormholing • Distributed traffic aggregation for Network Intrusion Detection Systems • Wormhole • Tunnel traffic from a remote sensor to backend NIDS • VTL mechanisms for packet capture and injection • Cooperative • Volunteer machines aggregate traffic • VTL implementation cross platform • Selective • Aggregates traffic that Volunteer client is not interested in • VTL mechanisms for packet inspection • J. Lange, P. Dinda, and F. Bustamante, Vortex: Enabling Cooperative Selective Wormholing for Network Security Systems, Proceedings of the 10th International Symposium on Recent Advances in Intrusion Detection (To Appear)

  30. Future Work • Generalizable to complete IO framework • Performance • VMM based implementation • Automatic Service Adaptation

  31. Conclusion • Transparent Network Services allow high level transformations of low level network traffic • VTL • A framework for creating Transparent Network Services • Wide range of potential services • Many useful for HPDC

  32. Prescience Lab • http://plab.cs.northwestern.edu • Virtuoso • http://virtuoso.cs.northwestern.edu • John Lange • http://www.artifex.org/~jarusl

  33. Vortex • Cooperative Selective Wormhole implementation • VTL • Traffic capture and injection • Packet modifications • Rewrite addresses • Anonymize packets • Cross platform functionality

  34. Vortex Architecture VM Based Honeypot Commodity PC IDS Analysis Backend Windows/UNIX VM VNET Proxy Apps Vortex Physical Honeypot Operating System VTL Firewall PCAP libnet NIC VNET Overlay Backend Network

  35. Subnet Tunneling VNET Proxy (PROXY1) Gateway (GW1) VM1 LAN connection Internet VNET Overlay Gateway Router VM2 Gateway (GW2) VNET Proxy (PROXY2)