CSC 401 Data and Computer Communications Networks

Transcription

1 CSC 401 Data and Computer Communications Networks Network Layer ICMP (5.6), Network Management(5.7) & SDN (5.1, 5.5, 4.4) Prof. Lina Battestilli Fall 2017

2 Outline 5.6 ICMP: The Internet Control Message Protocol 5.7 Network management and SNMP Software Defined Networks 5.1 SDN vs. Traditional Networking SDN Controllers & Applications Openflow Protocol 4.4 Generalized Forwarding & SDN SDN Examples & Discussion

3 ICMP: internet control message protocol used by hosts & routers to communicate network-level information error reporting: unreachable host, network, port, protocol echo request/reply (used by ping) network-layer above IP: ICMP msgs carried in IP datagrams ICMP message: Type Code first 8 bytes of IP datagram causing error Type Code description 0 0 echo reply (ping) 3 0 dest. network unreachable 3 1 dest host unreachable 3 2 dest protocol unreachable 3 3 dest port unreachable 3 6 dest network unknown 3 7 dest host unknown 4 0 source quench (congestion control - not used) 8 0 echo request (ping) 9 0 route advertisement 10 0 router discovery 11 0 TTL expired (traceroute) 12 0 bad IP header

4 Traceroute and ICMP source sends series of UDP segments to dest first set has TTL =1 second set has TTL=2, etc. unlikely port number when nth set of datagrams arrives to nth router: router discards datagrams and sends source ICMP messages (type 11, code 0) ICMP messages includes name of router & IP address when ICMP messages arrives, source records RTTs stopping criteria: UDP segment eventually arrives at destination host destination returns ICMP port unreachable message (type 3, code 3) source stops 3 probes 3 probes 3 probes

5 Outline 5.6 ICMP: The Internet Control Message Protocol 5.7 Network management and SNMP Software Defined Networks 5.1 SDN vs. Traditional Networking 5.5 SDN Control Plane SDN Controllers & Applications Openflow Protocol 4.4 Generalized Forwarding & SDN SDN Examples & Discussion

6 What is network management? autonomous systems (aka network ): 1000s of interacting hardware/software components other complex systems requiring monitoring, control: jet airplane nuclear power plant others? "Network management includes the deployment, integration and coordination of the hardware, software, and human elements to monitor, test, poll, configure, analyze, evaluate, and control the network and element resources to meet the real-time, operational performance, and Quality of Service requirements at a reasonable cost." 7

7 Infrastructure for network management definitions: managing entity managing entity network management protocol data agent data managed device agent data managed device agent data managed device agent data managed device agent data managed device managed devices contain managed objects whose data is gathered into a Management Information Base (MIB) 8

8 SNMP protocol Two ways to convey MIB info, commands: managing entity managing entity request response trap msg agent data agent data managed device managed device request/response mode trap mode 9

9 SNMP protocol: message types Message type GetRequest GetNextRequest GetBulkRequest Function manager-to-agent: get me data (data instance, next data in list, block of data) InformRequest manager-to-manager: here s MIB value SetRequest manager-to-agent: set MIB value Response Agent-to-manager: value, response to Request Trap Agent-to-manager: inform manager of exceptional event 10

10 SNMP protocol: message formats Get/set header Variables to get/set PDU type (0-3) Request ID Error Status (0-5) Error Index Name Value Name Value. PDU type 4 Enterprise Agent Addr Trap Type (0-7) Specific code Time stamp Name Value. Trap header Trap info SNMP PDU More on network management: see earlier editions of text! Typically carried in UDP 11

11 Outline 5.6 ICMP: The Internet Control Message Protocol 5.7 Network management and SNMP Software Defined Networks 5.1 SDN vs. Traditional Networking SDN Controllers & Applications Openflow Protocol 4.4 Generalized Forwarding & SDN SDN Examples & Discussion

12 Traditional Networks MANAGEMENT PLANE: Collect measurements and configure the equipment Routing Algorithm CONTROL PLANE: Distributed Algorithms, track topology changes, compute routes, install forwarding rules DATA PLANE: Forward, filter, buffer, mark, rate-limit, and measure packets 13

13 Traffic engineering: difficult traditional routing 5 u 1 2 v x w y 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 control knobs : wrong! 14

14 Traffic engineering: difficult traditional routing 5 u 1 2 x v w y 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) 15

15 16 y x w v z u v x w y 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) Traffic engineering: difficult traditional routing

16 SDN: logically centralized control plane A distinct (typically remote) controller interacts with local control agents (CAs) in routers to compute forwarding tables Remote Controller CA CA CA CA CA control plane data plane ~2005: renewed interest in rethinking network control plane 17

17 SDN Key Characteristics Characteristic Flow Based Forwarding Separation of Data and Control Plane Network Control Functions: external to data-lane switches A programmable network Some Detail packet forwarding on much more than IP dst address Data Plane: match plus action Control Plane: determines/manages the flow tables in the packet switches Software executes on servers that are both distinct and remote from the network's switches. Network applications use the SDN API to control the network devices. D. Kreutz et al, Software-Defined Networking: A Comprehensive Survey, Proceedings of the IEEE,

18 1980s Mainframes AppAppAppAppAppAppAppAppAppAppApp Specialized Applications Specialized Operating System Specialized Hardware Windows Open Interface Linux (OS) or or Open Interface Microprocessor Mac OS Vertically integrated Closed, proprietary Slow innovation Small industry Horizontal Open interfaces Rapid innovation Huge industry Slide from Nick McKeown s talk Making SDN Work at the Open Networking Summit, April

19 Routers/Switches AppAppAppAppAppAppAppAppAppAppApp Specialized Features Specialized Control Plane Specialized Hardware Control Open Interface Control Plane Plane or or Open Interface Merchant Switching Chips Control Plane Vertically integrated Closed, proprietary Slow innovation Horizontal Open interfaces Rapid innovation 20

20 Outline 5.6 ICMP: The Internet Control Message Protocol 5.7 Network management and SNMP Software Defined Networks 5.1 SDN vs. Traditional Networking SDN Controllers & Applications Openflow Protocol 4.4 Generalized Forwarding & SDN SDN Examples & Discussion

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

22 SDN perspective: SDN controller SDN controller (network OS): maintain network state information interacts with network control 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-control applications access control load balance northbound API SDN Controller (network operating system) southbound API control plane data plane 5- SDN-controlled switches

23 SDN perspective: control applications network-control apps: brains of control: implement control functions using lower-level services, API provided by SND controller unbundled: can be provided by 3 rd party: distinct from routing vendor, or SDN controller routing network-control applications access control load balance northbound API SDN Controller (network operating system) control plane southbound API data plane SDN-controlled switches 24

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

25 Outline 5.6 ICMP: The Internet Control Message Protocol 5.7 Network management and SNMP Software Defined Networks 5.1 SDN vs. Traditional Networking SDN Controllers & Applications Openflow Protocol 4.4 Generalized Forwarding & SDN SDN Examples & Discussion

26 OpenFlow protocol OpenFlow Controller operates between SDN controller, switch TCP used to exchange messages optional encryption Three classes of OpenFlow messages: Controller-to-Switch Asynchronous (Switch-to-Controller) Symmetric (misc) Open Networking Foundation (ONF), a user-led organization dedicated to promotion and adoption of SDN manages the OpenFlow standard. 5-27

27 OpenFlow: Controller-to-Switch Messages Key Controller-to-Switch messages features: controller queries switch features, switch replies configure: controller queries/sets switch configuration parameters modify-state: add, delete, modify flow entries in the OpenFlow tables packet-out: controller can send this packet out of specific switch port OpenFlow Controller 5-28

28 OpenFlow: Switch-to-Controller Messages Key Switch-to-Controller messages packet-in: transfer packet (and its control) to controller. See packet-out message from controller flow-removed: flow table entry deleted at switch port status: inform controller 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 controller 5-29

29 Outline 5.6 ICMP: The Internet Control Message Protocol 5.7 Network management and SNMP Software Defined Networks 5.1 SDN vs. Traditional Networking SDN Controllers & Applications Openflow Protocol 4.4 Generalized Forwarding & SDN SDN Examples & Discussion

30 Longest Destination IP-prefix Forwarding routing algorithm local forwarding table dest address output link address-range 1 address-range 2 address-range 3 address-range routing algorithm determines end-end-path through network forwarding table determines local forwarding at this router IP destination address in arriving packet s header 1 3 2

31 Generalized Forwarding and SDN Each router contains a flow table that is computed and distributed by a logically centralized routing controller logically-centralized routing controller control plane data plane local flow table headers counters actions values in arriving packet s header

32 OpenFlow data plane abstraction flow: defined by header fields generalized forwarding: simple packet-handling rules Pattern: match values in packet header fields Actions: for matched packet: drop, forward, modify, matched packet or send matched packet to controller Priority: disambiguate overlapping patterns Counters: #bytes and #packets * : wildcard 1. src=1.2.*.*, dest=3.4.5.* drop 2. src = *.*.*.*, dest=3.4.*.* forward(2) 3. src= , dest=*.*.*.* send to controller 33

33 OpenFlow: Flow Table Entries Rule Action Stats Packet + byte counters 1. Forward packet to port(s) 2. Encapsulate and forward to controller 3. Drop packet 4. Send to normal processing pipeline 5. Modify Fields Switch Port VLAN ID MAC src MAC dst Eth type IP Src IP Dst IP Prot TCP sport TCP dport Link layer Network layer Transport layer 34

34 Destination-based forwarding: Switch Port * Switch Port * MAC src MAC dst Eth type VLAN ID IP Src IP Dst IP Prot TCP sport TCP dport Action * * * * * * * * port6 IP datagrams destined to IP address should be forwarded to router output port 6 Firewall: Switch Port * MAC src MAC dst Eth type VLAN ID IP Src IP Dst IP Prot TCP sport TCP dport Forward * * * * * * * * 22 drop do not forward (block) all datagrams destined to TCP port 22 MAC src MAC dst Eth type Examples VLAN ID IP Src IP Dst IP Prot TCP sport TCP dport Forward * * * * * * * * drop do not forward (block) all datagrams sent by host Destination-based layer 2 (switch) forwarding: Switch Port * MAC src 22:A7:23: 11:E1:02 MAC dst Eth type VLAN ID IP Src IP Dst IP Prot TCP sport TCP dport Action * * * * * * * * port3 layer 2 frames from MAC address 22:A7:23:11:E1:02 should be forwarded to output port 3

35 OpenFlow abstraction match+action: unifies different kinds of devices Router match: longest destination IP prefix action: forward out a link Switch match: destination MAC address action: forward or flood Firewall match: IP addresses and TCP/UDP port numbers action: permit or deny NAT match: IP address and port action: rewrite address and port Network Layer: Data Plane 4-36

36 OpenFlow example match IP Src = 10.3.*.* IP Dst = 10.2.*.* action forward(3) Host h Example: datagrams from hosts h5 and h6 should be sent to h3 or h4, via s1 and from there to s2 2 1 s3 controller Host h match ingress port = 1 IP Src = 10.3.*.* IP Dst = 10.2.*.* Host h action forward(4) s1 4 Host h Host h s2 4 match ingress port = 2 IP Dst = ingress port = 2 IP Dst = Host h action forward(3) forward(4)

37 Outline 5.6 ICMP: The Internet Control Message Protocol 5.7 Network management and SNMP Software Defined Networks 5.1 SDN vs. Traditional Networking SDN Controllers & Applications Openflow Protocol 4.4 Generalized Forwarding & SDN SDN Examples & Discussion

38 SDN: control/data plane interaction example network graph statistics Link-state info s1 Dijkstra s link-state Routing OpenFlow 1 2 RESTful API host info s3 s2 flow tables SNMP s4 intent switch info S1, experiencing link failure using OpenFlow port status message to notify controller SDN controller 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 controller, computes new routes 39

39 SDN: control/data plane interaction example Dijkstra s link-state Routing network graph statistics 3 Link-state info 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 controller, which computes new flow tables needed Controller uses OpenFlow to install new tables in switches that need updating 1 s1 s2 s4 40

40 OpenDaylight (ODL) controller Network service apps Access Control Traffic Engineering REST Basic Network Service Functions topology manager API forwarding manager switch manager host manager Service Abstraction Layer (SAL) stats manager ODL Lithium controller network apps may be contained within, or be external to SDN controller Service Abstraction Layer: interconnects internal, external applications and services OpenFlow 1.0 SNMP OVSDB 41

41 ONOS controller Network control 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 control apps separate from controller intent framework: high-level specification of service: what rather than how considerable emphasis on distributed core: service reliability, replication performance scaling

42 SDN Benefits Why a logically centralized control plane? easier network management: avoid router misconfigurations, greater flexibility of traffic flows table-based forwarding 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 control plane 5-43

43 SDN: selected challenges hardening the control plane: dependable, reliable, performance-scalable, secure distributed system robustness to failures: leverage strong theory of reliable distributed system for control plane dependability, security: baked in from day one? networks, protocols meeting mission-specific requirements e.g., real-time, ultra-reliable, ultra-secure Internet-scaling Network Layer: Control Plane 5-44

44 References Some of the slides are identical or derived from 1. Slides for the 7 th edition of the book Kurose & Ross, Computer Networking: A Top-Down Approach, 2. Slide from Nick McKeown s talk Making SDN Work at the Open Networking Summit, April Computer Networking, Nick McKeown and Philip Levis, 2014 Stanford University