Endsystem Support for Network Virtualization

1. Endsystem Support for Network Virtualization Fred Kuhns

2. Overview • Network Diversification: • Virtual network (vNet): distinct vNets coexist within a common physical network • Diversification layer: common substrate to share physical resources and provide isolation • vNet is composed of one or more virtual routers (VR) interconnected by virtual links. Virtual routers and links are direct corollaries to their physical counterparts … Network resources are virtualized. • An end-system implements vNet protocols and provides connectivity services within a virtualized network protocol environment (virtual end-system). The virtual end-system provides mechanisms for protocol implementation, resource control and isolation. • Diversification layer provides two levels of abstraction (i.e. two core services): • Substrate: encapsulate existing layer 1 and layer 2 technologies and provide a single, consistent framework for implementing virtualized links and routers. substrate link: abstraction to provide similar behavior as a point-to-point connection between communicating end points. Provides isolation services to different virtual networks using a common substrate link. substrate router: A physical device which forwards network traffic based on its vNet membership. Provides sharing and isolation services to disparate vNets and hosts virtual routers. • Virtual: framework providing a simple model and set of interfaces for implementing virtual networks. The model defines virtual routers, end-systems and links. The goal is for virtual inks to and routers to behave similar to their physical counterparts. virtual link: simulates the behavior of a dedicted point-to-point link interconnecting virtual end points (virtual routers and/or virtual end systems). A virtual link is implemented by one or more substrate links. virtual router: implements a particular vNet’s routing logic. The underlying substrate router provides the necessary isolation and resource management functions.

3. vNet Discussion • Develop examples/scenarios • intranet (no routing) use existing model • internet (routing) use diversified networking model • use Ethernet and virtualized IP as running example • Model: Simple • network devices interconnected through simplex, point-to-point links. • common link layer protocol used for delivering packetized data to neighbor (not end-to-end but hop to hop) • Achieving this model • context: shared heterogeneous physical network, links and packet switches (aka packet routers) • objectives: • partition physical resources into virtual links and routers • isolation mechanisms for virtualized resources • bind virtualized resources to network instances

4. Context: Network Diversification (vNets) substrate link substrate router virtual router virtual link virtual end-system

5. switched LAN Simulates Star Topology for Substrate Links … VLANX1 VLANX2 VLANXN • Internetworking over a diversified network • Substrate function with Ethernet: • Substrate links: use VLANs to provide the equivalent of a virtualized “wire” connecting an endsystem to a specific substrate router. • Sharing and Isolation: • All vNet traffic use assigned VLANs • Use priority queuing (802.1P/Q) • All intranet traffic uses lower priority queues. • Resource management: • LAN: Use admission control (static or dynamic) to provide bandwidth guarantees to vNet traffic. • End system: Substrate layer on end-system enforce per VLAN and per vNet bandwidth constraints • Virtual links: In this simple example there is exactly one virtual link for each substrate link. vNetX VR1 • Each host to substrate router connection is assigned a distinct VLAN. So N hosts implies N VLANs on Ethernet. • Alternative is to define one VLAN tree for each protocol suite (i.e. vnet).

6. Low High Low High Low High Low High Traffic isolation with priority aware substrate … Ethernet Hub with High and Low Priority TX queues vNet traffic to High otherwise Low Local control/management; Legacy internet traffic all vNet traffic vNet traffic (internet) vNetX VR1 Local traffic (intranet)

7. ethernet switched LAN Substrate Link as a VLAN Tree … • Internetworking over a diversified network • Substrate function with Ethernet: • Substrate links: The VLAN creates a tree interconnecting all end-systems to the substrate router. Substrate end-point then uses the VLAN tag and source/destination address to realize the logical point-to-point substrate link. • Sharing and Isolation: • no change from substrate star topology. The only difference is the shared VLAN domain. Scheme provides traffic isolation. • Resource management: • Same • Virtual links: Same. VLANX

8. ethernet switched LAN Multiple Substrate Links … • Internetworking over a diversified network • Substrate function with Ethernet: • Substrate links: Three VLAN trees are used for all virtual net traffic to/from a substrate router: • Low priority: default for best-effort traffic • Medium priority for virtual nets with soft performance requirements (average bandwidth) • High priority for isochronous or low-delay, interactive applications • Sharing and Isolation: See above. • Resource management: See above • Virtual links: Same. VLANdgram VLANhigh VLANmed

9. VR1 VLI VLI VLI VR1 VLI VLI Multiple vNets per Host … virtual interface ether addr/vlan ether addr/vlan ether addr/vlan substrate interface VLAN1 VLAN2 VLAN3 • The full model: • Substrate link: connects end-system to substrate router. Virtualization of a physical cable or wire. A packet enters one end, exists the other and is opaque within. • Simplex or Duplex? • Substrate interface: end-system abstraction • Ethernet: <interface, VLAN, dst_addr> • tunnel: MPLS, IP, IPsec, L2TPv3, GRE, AToM • Layer 2: ATM, others? • Virtual link: Logical interconnection (virtual wire) of adjacent vNet nodes. • Point-to-point, Simplex or Duplex? • Virtual interface: end-system abstraction representing one end of a virtual link. Substrate defines mechanism for multiplexing onto common substrate link. For example a virtual link identifier (VLI) in a substrate header • Simplex or Duplex? ethernet LAN VLAN tag and dst addr identify substrate router. VLI tag used to router pkt substrate interfaces virtual interface

10. Multiple next hop VRs vNetX VR2 vNetX VR3 Host A member of vNetX and vNetY substrate router 2 substrate router 3 VLI1 VLI1 enetAddrSR2 enetAddrSR3 enetAddrA VLANA3 VLANA2 • Multiple Next Hop Virtual Routers: • Substrate link: per end-system, substrate router pair. • Substrate interface: three substrate interfaces: • SI1 = <eth0, VLANXA1, enetAddrSR1> • SI2 = <eth0, VLANXA2, enetAddrSR2> • SI3 = <eth0, VLANXA3, enetAddrSR3> • Virtual link: Logical point-to-point connection between virtual end-system and access virtual router. Since we model a point-to-point link there is no need for link addresses. • Virtual interface: Representation of virtual link on the end-system. The substrate assigns a per substrate link, virtual link identifier (VLI) for each virtual link. • VI1 = <SI1, VLI1> • VI2 = <SI1, VLI2> • VI3 = <SI2, VLI1> • VI4 = <SI3, VLI1> ethernet switched LAN VLANA1 enetAddrSR1 VLI1 VLI2 vNetX VR1 vNetY VR1 substrate router 1

11. VLI VLI VLAN VLI TCP/IP as an Example Protocol vNet Protocl = IP vNet framework vint0 eth0 standard ethernet Interface … VLANX eth0 direct connect ethernet device VLANX ethernet LAN Substrate Interface: Directly connected: destination IP address + ARP = enet addr Gateway: (Gateway’s IP + ARP = enet addr) + VLAN Virtual Interface: Directly connected: Not used, model only for internetworking Gateway: VLI assigned by substrate. How is this integrated into the current ARP/route interface? ethernet dest. addr Substrate Router SR1 IP

12. Using Tunnels for the substrate layer • Need to look into the various tunneling approaches/protocols. How can we leverage these? • MPLS and MPLS VPNs • Generic Routing Encapsulation (GRE): RFC 2784 • Point-to-point tunneling protocol (PPTP) • Secure VPN • Any transport over MPLS (AToM) • IP tunnel • IPsec VPNs • Layer 2 Tunneling Protocol version 3 (L2TPv3) • version3 is a draft standard • RFC 2661: Layer 2 tunneling protocol • 802.1Q Tunneling: Cisco 802.1Q-in-Q VLAN Extension Services • What about MPLS over IP tunnels: what was done there?

13. File Interface ops TCP module … TCP1 TCP2 TCPn FS management Basic I/O Interface RAW IP UDP open files buffer cache tasks device driver txqueue rxqueue OS Kernel Block Diagram User Space (Applications) Socket Interface ops AST Processing callback routes IP task management SW int (AST) util TCP TC/ AST poll qdisc scheduler callout Q hardware independent layer clock handler process accounting scheduling time management Device independent I/O ethernet Interrupt Processing hardware dependent layer configuration: registers, MMU (TLB, cache, VM) bus and peripherals System Exception handlers eth0 uart timer OS ISR demux Hardware HW interrupt/Exception

14. User or kernel Space protocols? • Each has pros and cons • User space protocols: • easier to implement and debug • easier to introduce new protocols (not tightly dependent on socket layer knowing about the new protocol) • easier to isolate and protect protocols and apps from each other (leverage process model) • kernel level protocols • easier to integrate into existing framework (simplifies support for system interface functions like select/poll) • simplifies intra-protocol security and protection (since protocol runs within trusted kernel) • simplifies (well, more direct) kernel demultiplexing to correct protocol context (endpoint) • increased efficiency

15. User Space Protocol Implementation • Uncommon outside of high-performance community, they want zero-copy and specialized demux keys. • Problems: asynchronous processing, life cycle, authentication and demultiplexing to endpoints • latency in delivering packets (i.e. acks) to user space • increased overhead in per packet processing before a drop/keep decision is made • processing received acks • timeouts and retransmissions • establishing connections and security: snooping, masquerading • supporting select and poll • protocols where connection may outlive process (TCP’s TIMED_WAIT) • global routing and address resolution tables • global connection tables • need to know what other ports are being used (locally) • accepting/rejecting new connections

16. Assumptions • Assumptions: • Applications using different VNs (or no VN) will need to communicate using the various IPC mechanisms • We want to manage all aspects of Network I/O but not the use of other traditional resources (memory, files etc) • CPU, memory and interface bandwidth controlled at the virtual net granularity • intra-VN, implementers should have the mechanisms to support QoS and Security • simple mechanism for adding new protocols/VNs

17. User Space Protocols • Chandramohan A. Thekkath , Thu D. Nguyen , Evelyn Moy , Edward D. Lazowska, Implementing network protocols at user level, IEEE/ACM Transactions on Networking (TON), v.1 n.5, p.554-565, Oct. 1993 • Chris Maeda, Brian Bershad, Protocol Service Decomposition for High-Performance Networking, Proceedings of the 14th ACM Symposium on Operating Systems Principles. December 1993, pp. 244-255. • Aled Edwards , Steve Muir, Experiences implementing a high performance TCP in user-space, Proceedings of the conference on Applications, technologies, architectures, and protocols for computer communication, p.196-205, 1995 • Kieran Mansley, Engineering a User-Level TCP for the CLAN Network, Proceedings of the ACM SIGCOMM workshop on Network-I/O convergence: experience, lessons, implications, Pages: 228 – 236, 2003

18. user-space protocols: Global Issues • Routing: Direct packets to/from correct endpoint/interface • How is traffic demultiplexed and sent to the correct endpoint/process? • In-kernel filters • Where are the routing tables and how are they maintained? • route fixed when connection established or located in shared memory • Control: I use IPv4 as an example • Address resolution protocols/tables? • Other control protocols. For example ICMP, IGRP, others? • Where are the routing protocols implemented? • Management: • Must manage a protocols namespace (for example, port numbers in IPv4). • Common programming technique, allow protocol instance to select local address part • specify port = 0 and addr = 0 then implementation will assign correct values • Passive connect model? • In IPv4 a server listens on a port (host:port:proto) for a connection request. To establish a connection a unique (to the endsystem) port number is assigned and new socket allocated. • socket-oriented system calls must be supported. On UNIX must support non-blocking I/O with select and poll. • Connection lifetime may outlast process. • For example TCP TIME_WAIT or simply waiting for a final ack or resending if no ack received. • Security: we must provide sufficient mechanisms for protocol developers • implementations must be able to guard against masquerading and eavesdropping

19. User Space: Configurations • Given these global issues there are two likely configurations: • all traffic passes through common protocol daemon in user space • control daemon implements basic set of control functions while user library implements majority of data path functions • prior work has shown the latter approach to be superior. • Having all traffic pass through a common protocol daemon => at least one extra copy operation (kernel -> daemon -> user process) • A better solution is for a daemon to insert relatively simple packet filters in kernel for established connections which directs packets to/filters packets from endpoints.

20. application vnetX: protocol library User-Space: Passive Open 0. listen/accept (passive open) vnetX control daemon: (namespace, lifecycle, connections) 4. new connection data copy socket layer 3. insert incoming and outgoing filters for vnetX connection 1. connection request (in) 5. data, established connections compare against connection specific outgoing filter 2. ack (out) vnet demux connection filters use VLI to access incoming filters and use to demux to filter set and/or socket. ethernet

21. application vnetX: protocol library User-Space: Active Open 0. connect vnetX control daemon: (namespace, lifecycle, connections) 4. new connection data copy socket layer 1. connection request (out) 3. insert incoming and outgoing filters for vnetX connection 5. data, established connections compare against connection specific outgoing filter 2. ack (in) vnet demux connection filters use VLI to access incoming filters and use to demux to filter set and/or socket. ethernet

22. application vnetX: protocol library User-Space: Datagram (Connectionless) daemon fills in local address and binds to socket. No restrictions on destination 0. open(any) vnetX control daemon: (namespace, lifecycle, connections) data copy 2. new connection (local address) socket layer 1. insert incoming and outgoing filters for vnetX connection 3. data established connections compare against “connection” specific outgoing filter vnet demux connection filters use VLI to access incoming filters and use to demux to socket. In this case only the local part is used. ethernet

23. application vnetX: protocol library User-Space: Datagram (Connectionless) daemon fills in both local and destination addresses. Destination restricted 0. open(local and remote addr) vnetX control daemon: (namespace, lifecycle, connections) 2. new connection(local and remote) data copy socket layer 1. insert incoming and outgoing filters for vnetX connection 3. data established connections compare against “connection” specific outgoing filter vnet demux connection filters ethernet use VLI to access incoming filters and use to demux to socket.

24. application vnetX: protocol library User-Space: App exits TCP enters TIME_WAIT after close vnetX control daemon: (namespace, lifecycle, connections) socket layer 3. remove filters 1. connection close (out) 2. ack (in/out) vnet demux connection filters ethernet drop

25. Extensible protocol frameworks in the kernel • Herbert Bos, Bart Samwel, Safe Kernel Programming in the OKE, Proceedings of the fifth IEEE Conference on Open Architectures and Network Programming, June 2002

26. OKE • Context: For performance reasons it is useful to permit third parties to load optimized modules into the kernel • Problem: Third party code is untrusted so loading into kernel will compromise system security and reliability. Could use safe execution environment like java but incurs expensive runtime checks. • Solution: create set of mechanisms and policies to permit non-root users to safely load untrusted application modules into kernel space with minimal impact on runtime performance. • Safety: use a trusted compile to enforce policies (constraints). The constraints are designed to ensure the untrusted module will not adversely affect the kernel (core and loadable modules) or unrelated processes. • Userprivileges: Vary enforced constraints based on user privileges (customizable language) • Termination: well defined termination boundaries to protect system state • Enforcement: Static and dynamic checks; language extensions • Ease of use: Familiar development environment using Cyclone (type safe, C extension) and kernel module. • Contribution: definition of safe kernel programming environment that meets competing needs: • performance • safety • ease of use • hosted in a commodity OS

27. Considerations • Identified areas where modules may impact system behavior • program correctness: language restrictions for safety and enforce coding conventions • Memory access: static and dynamic enforcement of memory access rules • Kernel module access: static and dynamic enforcement of kernel module (interface) access restrictions • Resource usage: Bounded (deterministic or limited)

28. Pushing protocols into the Kernel • Positives: • All the issues associated with user-space protocol simply go away. Global tables and lifetime of the kernel • Performance, efficiency, existing code base • Enhances intra-Protocol security • Simplifies integration with existing network I/O subsystems and interfaces • Negatives: • Isolation: More difficult to isolate system from protocol instances. Inter-protocol isolation difficult. • Security: Proving trust/security more difficult • Implementation and debugging more difficult in kernel

29. ops File Interface PF_VNET PF_INET FS management Socket Interface I/O Interface open files buffer cache Socket I/O Interface vnet ops vnet Proto vnet Proto state tables state tables ethetnet vnet Demux eth device driver eth0 VLAN Kernel-Space Protocols Rework! Application(s) /dev/protoX /dev/vnet User Space (Applications) … vnet:ep vnet:ep tcp:port udp:port rawIP … TCP vnet RAW IP UDP TCP1 TCP2 … TCPn TCP/IP … IP route to interface routes SW Interrupt HW Interrupt Hardware HW interrupt/Exception