Network Layer: The Control Plane

Transcription

1 Network Layer: The Control Plane 7 th Edition, Global Edition Jim Kurose, Keith Ross Pearson April 06 5-

2 Software defined networking (SDN) Internet network layer: historically has been implemented via distributed, per-router approach monolithic router contains switching hardware, runs proprietary implementation of Internet standard protocols (IP, RIP, IS-IS, OSPF, BGP) in proprietary router OS (e.g., Cisco IOS) different middleboxes for different network layer functions: firewalls, load balancers, NAT boxes,.. ~005: renewed interest in rethinking network 5-

3 Per-router Individual routing algorithm components in each and every router interact with each other in to compute forwarding tables Routing Algorithm data 5-3

4 Logically centralized A distinct (typically remote) ler interacts with local agents (CAs) in routers to compute forwarding tables Remote Controller CA CA CA CA CA data 5-4

5 Software defined networking (SDN) Why a logically centralized? easier network management: avoid router misconfigurations, greater flexibility of traffic flows table-based forwarding (recall OpenFlow API) allows programming routers centralized programming easier: compute tables centrally and distribute distributed programming: more difficult: compute tables as result of distributed algorithm (protocol) implemented in each and every router open (non-proprietary) implementation of 5-5

6 Analogy: mainframe to PC evolution * Specialized Applications Specialized Operating System Specialized Hardware Ap App p Ap p Windows (OS) Ap p Ap p Ap p Ap p Ap p Ap p Open Interface or Linux or Open Interface Ap p Microprocessor Ap p Mac OS Vertically integrated Closed, proprietary Slow innovation Small industry Horizontal Open interfaces Rapid innovation Huge industry * Slide courtesy: N. McKeown 5-6

7 Traffic engineering: difficult traditional routing 5 u v x 3 3 w y 5 z Q: what if network operator wants u-to-z traffic to flow along uvwz, x-to-z traffic to flow xwyz? A: need to define link weights so traffic routing algorithm computes routes accordingly (or need a new routing algorithm)! Link weights are only knobs : wrong! 5-7

8 Traffic engineering: difficult 5 u v x 3 3 w y 5 z Q: what if network operator wants to split u-to-z traffic along uvwz and uxyz (load balancing)? A: can t do it (or need a new routing algorithm) 5-8

9 Traffic engineering: difficult Networking 40 5 u v v x x 3 3 w w y y 5 z z Q: what if w wants to route blue and red traffic differently? A: can t do it (with destination based forwarding, and LS, DV routing) 5-9

10 Software defined networking (SDN) 4. programmable applications routing access Remote Controller load balance 3. functions external to data switches data CA CA CA CA CA., data separation : generalized flowbased forwarding (e.g., OpenFlow) 5-0

11 SDN perspective: data switches Data switches fast, simple, commodity switches implementing generalized data- forwarding (Section 4.4) in hardware switch flow table computed, installed by ler API for table-based switch (e.g., OpenFlow) defines what is lable and what is not protocol for communicating with ler (e.g., OpenFlow) routing network- applications access load balance northbound API SDN Controller (network operating system) southbound API data 5- SDN-led switches

12 SDN perspective: SDN ler SDN ler (network OS): maintain network state information interacts with network applications above via northbound API interacts with network switches below via southbound API implemented as distributed system for performance, scalability, fault-tolerance, robustness routing network- applications access load balance northbound API SDN Controller (network operating system) southbound API data 5- SDN-led switches

13 SDN perspective: applications network- apps: brains of : implement functions using lower-level services, API provided by SND ler unbundled: can be provided by 3 rd party: distinct from routing vendor, or SDN ler routing network- applications access load balance northbound API SDN Controller (network operating system) southbound API data 5-3 SDN-led switches

14 Components of SDN ler Interface layer to network apps: abstractions API Network-wide state management layer: state of networks links, switches, services: a distributed database communication layer: communicate between SDN ler and led switches routing network graph Network-wide distributed, robust state management Link-state info statistics OpenFlow access RESTful API host info load balance Interface, abstractions for network apps flow tables SNMP intent switch info Communication to/from led devices SDN ler 5-4

15 OpenFlow protocol OpenFlow Controller operates between ler, switch TCP used to exchange messages optional encryption three classes of OpenFlow messages: ler-to-switch asynchronous (switch to ler) symmetric (misc) 5-5

16 OpenFlow: ler-to-switch messages Key ler-to-switch messages features: ler queries switch features, switch replies configure: ler queries/sets switch configuration parameters modify-state: add, delete, modify flow entries in the OpenFlow tables packet-out: ler can send this packet out of specific switch port OpenFlow Controller 5-6

17 OpenFlow: switch-to-ler messages Key switch-to-ler messages packet-in: transfer packet (and its ) to ler. See packetout message from ler flow-removed: flow table entry deleted at switch port status: inform ler of a change on a port. OpenFlow Controller Fortunately, network operators don t program switches by creating/sending OpenFlow messages directly. Instead use higher-level abstraction at ler 5-7

18 SDN: /data interaction example network graph statistics Link-state info s Dijkstra s link-state Routing OpenFlow RESTful API host info s3 s flow tables SNMP s4 intent switch info 3 4 S, experiencing link failure using OpenFlow port status message to notify ler SDN ler receives OpenFlow message, updates link status info Dijkstra s routing algorithm application has previously registered to be called when ever link status changes. It is called. Dijkstra s routing algorithm access network graph info, link state info in ler, computes new routes 5-8

19 SDN: /data interaction example Dijkstra s link-state Routing network graph statistics 3 Link-state info 4 5 OpenFlow RESTful API host info flow tables SNMP intent switch info 5 6 link state routing app interacts with flow-table-computation component in SDN ler, which computes new flow tables needed Controller uses OpenFlow to install new tables in switches that need updating s s3 s s4 5-9

20 OpenDaylight (ODL) ler Network service apps Access Control Traffic Engineering REST API Basic Network Service Functions topology manager forwarding manager switch manager host manager Service Abstraction Layer (SAL) stats manager ODL Lithium ler network apps may be contained within, or be external to SDN ler Service Abstraction Layer: interconnects internal, external applications and services OpenFlow.0 SNMP OVSDB 5-0

21 ONOS ler Network apps REST hosts devices API Intent statistics device link host flow packet OpenFlow Netconf OVSDB northbound abstractions, protocols paths flow rules topology links ONOS distributed core southbound abstractions, protocols apps separate from ler intent framework: high-level specification of service: what rather than how considerable emphasis on distributed core: service reliability, replication performance scaling 5-

22 SDN: selected challenges hardening the : dependable, reliable, performance-scalable, secure distributed system robustness to failures: leverage strong theory of reliable distributed system for dependability, security: baked in from day one? networks, protocols meeting mission-specific requirements e.g., real-time, ultra-reliable, ultra-secure Internet-scaling 5-