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Preliminaries: EE807 Software-defined Networked Computing

Preliminaries: EE807 Software-defined Networked Computing. KyoungSoo Park Department of Electrical Engineering KAIST. routing algorithm. local forwarding table. header value. output link. 0100 0101 0111 1001. 3 2 2 1. value in arriving packet’s header. 1. 0111. 2. 3.

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Preliminaries: EE807 Software-defined Networked Computing

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  1. Preliminaries:EE807 Software-defined Networked Computing KyoungSoo Park Department of Electrical Engineering KAIST

  2. routing algorithm local forwarding table header value output link 0100 0101 0111 1001 3 2 2 1 value in arriving packet’s header 1 0111 2 3 Interplay Between Routing, Forwarding

  3. Intradomain Routing • Learning routes in an autonomous system (AS) • Also called “intraAS routing” • Two representative approaches • Distance vector (or Bellman-Ford) • Link state (or Dijkstra’s) • Time complexity • Per-node: O(nlogn) where n = # of nodes (routers)

  4. Distance Vector Algorithm • Strategy: each node exchanges its DV with its neighbor whenever link cost changes • DV contains the estimated cost to every node • Dynamic programming • Min path cost (x, y) = min(link cost(x,v) + path cost(v,y)) for all neighbor v of x • Implementation • Routing Information Protocol (RIP) • EIGRP (Cisco-proprietary): solves limitations of RIP

  5. Link State Algorithm • Strategy: flood the directly-connected link’s cost to every node • Send to all nodes, but the spread information is the local link cost • Link state packet (LSP) • Contains the link cost, id of the node, sequence number, TTL, etc. • Implementation • Open Shortest Path First (OSPF), Intermediate System-Intermediate System (IS-IS)

  6. Interdomain Routing • Intradomain routing: process of finding the least-cost path to network prefix X (in the same AS) • Interdomain routing: process of finding AS-level path that reaches the destination prefix X (not in the same AS) • Routing: coarse-grain path (interdomain) + fine-grain path (intradomain)

  7. Border Gateway Protocol (BGP) • The goal of interdomain routing • Find some loop-free path to the destination • Concerned with reachability than optimality • Concerned with the policies of ASs in the path • Finding path anywhere close to optimal is considered to be a great achievement • BGP advertises complete paths as an enumerated list of ASs to reach a particular network • Called a path-vector protocol • Example: 135.98/16: <AS3, AS7, AS10> • How do you detect a loop?

  8. Routers

  9. Router Functionality • Control plane: run routing protocols, run software on routing processor, circuit setup • Time scale: 10ms to second • Data plane: forwarding, buffering, filtering, scheduling, implemented in hardware • Time scale: nanoseconds • Management plane: administrator interface, analysis, configuration (traffic engineering) • Time scale: minutes to hours

  10. Router Architecture Overview data plane control plane

  11. Control/Data Separation decouple control and data planesby providing open standard API Borrowed from Jen Rexford’s slides

  12. (Logically) Centralized Controller Controller Platform Borrowed from Jen Rexford’s slides

  13. Protocols  Applications Controller Application Controller Platform Borrowed from Jen Rexford’s slides

  14. Software-defined Networking • Logically-centralized control plane • Why? fine-grained control of the traffic • No (traditional) routing protocols • Instead, there is a centralized controller • When a flow comes to a switch • The switch looks up forwarding table • If the entry is found, use it to forward packets • If not, it asks the controller to set up the route • OpenFlow is widely used to implement SDN • OpenFlow != SDN

  15. Middleboxes

  16. Middlebox • In-network devices that manipulate packets for purposes other than packet forwarding • Inspecting, filtering, transforming packets • Examples • Network address translators (NATs), firewalls, network intrusion detection systems (NIDSes), (performance enhancement, Web, WAN-accelerating) proxies, etc. • Recent trend • # of deployed middleboxes >> # of deployed routers

  17. Network Functions Virtualization • Motivation: difficult to manage many middlebox boxes • Each box runs different service • Configuration could be a nightmare • Conceptually, you have X units of Web proxy, Y units of NIDS, Z units of firewall • X, Y, Z are dynamically adjusting to the load • How to implement? • Virtualization: separate the service from physical infrastructure • Horizontal scaling (or scale out): add more nodes, install software, and turn them on • Vertical scaling (or scale up)?

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