Network Virtualization Jennifer Rexford Advanced Computer Networks http://www.cs.princeton.edu/courses/archive/fall08/cos561/ Tuesdays/Thursdays 1:30pm-2:50pm
Introduction Motivation for network virtualization Deployment dilemma, too many design goals, and coordination constraint Pluralist networks Economic refactoring Infrastructure and service providers Research challenges Systems challenges Resource allocation
The Internet: A Remarkable Story Tremendous success From research experiment to global communications infrastructure The brilliance of under-specifying Best-effort packet delivery service Key functionality at programmable end hosts Enabled massive growth and innovation Ease of adding hosts and link technologies Ease of adding services (Web, P2P, VoIP, ) But, change is easy only at the edge!
Rethinking the Network Architecture But, the Internet is showing signs of age Security, mobility, availability, manageability, Challenges rooted in early design decisions Weak notion of identity, tying address & location Not just a matter of redesigning a single protocol Revisit definition and placement of function What are the types of nodes in the system? What are their powers and limitations? What information do they exchange?
Hurdle #1: Deployment Dilemma An unfortunate catch-22 Must deploy an idea to demonstrate feasibility Can t get an undemonstrated idea deployed A corollary: the testbed dilemma Production network: real users, but can t change Research testbed: easy changes, but no users Bad for the research community Good ideas sit on the shelf Promising ideas do not grow up into good ones
Hurdle #2: Too Many Design Goals Many different system-engineering goals Scalability, reliability, security, privacy, robustness, performance guarantees, Perhaps we cannot satisfy all of them at once Applications have different priorities Online banking: security Web surfing: privacy, high throughput Voice and gaming: low delay and loss Compromise solution isn t good for anyone
Hurdle #3: Coordination Constraint Difficult to deploy end-to-end services Benefits only when most networks deploy No single network wants to deploy first Many deployment failures QoS, IP multicast, secure routing, IPv6, Despite solving real, pressing problems Increasing commoditization of ISPs sender 1 2 3 receiver
Virtualization to the Rescue Multiple customized architectures in parallel Multiple logical routers on a single platform Isolation of resources, like CPU and bandwidth Programmability for customizing each slice
Overcoming the Hurdles Deployment Dilemma Run multiple experimental networks in parallel Some are mature, offering services to users Isolated from others that are works in progress Too Many Design Goals Run multiple operational networks in parallel Customized to certain applications and users Coordination Constraint Run multiple end-to-end services in parallel Over equipment owned by different parties
Pluralist Future
The Case for Pluralism Suppose we can break down the barriers Enable realistic evaluation of new ideas Overcome the coordination constraint Maybe there isn t just one right answer Maybe the problem is over-constrained Too many goals, some of them conflicting Maybe the goals change over time And we ll always be reinventing ourselves The only constant is change So, perhaps we should design for change
Different Services, Different Goals Performance Low delay/jitter: VoIP and online gaming High throughput: bulk file transfer Security/privacy High security: online banking and e-commerce High privacy: Web surfing Scalability Very scalable: global Internet reachability Not so scalable: communication in small groups
Applications Within an Single ISP Customized virtual networks Security for online banking Fast-convergence for VoIP and gaming Specialized handling of suspicious traffic Testing and deploying new protocols Evaluate on a separate virtual network Rather than in a dedicated test lab Large scale and early-adopter traffic Leasing virtual components to others ISPs have unused node and link capacity Can allow others to construct services on top
Economic Refactoring in CABO Infrastructure Providers Service Providers Infrastructure providers: Maintain routers, links, data centers, and other physical infrastructure Service providers: Offer end-to-end services (e.g., layer 3 VPNs, SLAs, etc.) to users Today: ISPs try to play both roles, and cannot offer end-to-end services
Similar Trends in Other Industries Commercial aviation Infrastructure providers: Airports Infrastructure: Gates, hands and eyes support Service providers: Airlines SFO JFK PEK ATL E.g.: airplanes, auto industry, and commercial real estate
Communications Networks, Too! Two commercial examples in IP networks Packet Fabric: share routers at exchange points FON: resells users wireless Internet connectivity Broker FON economic refactoring Infrastructure providers: Buy upstream connectivity Service provider: FON as the broker (www.fon.com)
Enabling End-to-End Services Secure routing protocols Multi-provider Virtual Private Networks Paths with end-to-end performance guarantees Today Competing ISPs with different goals must coordinate Cabo Single service provider controls end-to-end path
Research Challenges
Virtualized and Programmable Routers Multiple routers on a single substrate Multiple control planes Multiple data planes Design trade-offs Speed: aggregate forwarding performance Getting close to raw forwarding speed Isolation: avoiding interference Avoiding jitter and resource contention Customization: programmability of the data plane Moving beyond IPv4 packets and Ethernet frames Software (e.g., Click) vs. hardware (e.g., NetFPGA)?
Control Frameworks Embedding virtual topology in physical one Finding suitable physical nodes and physical links With enough CPU, bandwidth, and memory and satisfying geographic and delay constraints Instantiating the virtual network Creating each virtual node and virtual link Reserving the necessary resources Monitoring the running system Detecting and diagnosing problems Providing measurement data to virtual network
Ways to Exploit Router Virtualization Exploiting the new capabilities in routers Separation of the physical from the logical Ability to run multiple routers in parallel Example: virtual router migration Moving router from one physical node to another E.g., for planned maintenance or service roll-out Example: bug-tolerant routers Running multiple instances of routing software and voting to protect the system from bugs
Discussion: Internet vs. Pluralism Internet architecture End-to-end argument Best-effort packet-delivery service Narrow waist of IP Separation of intradomain from interdomain Virtualized programmable networks Complete control within a virtual network Programmable functionality inside the network Different (virtual) networks for different services
Discussion: Experimental Infrastructure How to evaluate research ideas? Analysis Simulation Prototyping Deployment studies Importance of wide-area deployment? Realistic traffic and network conditions Real users and participation in experiments How real does real need to get? Will researchers bother to build and deploy? Incentives for conducting this kind of research