Overview. Ad Hoc and Wireless Mesh Networking. Ad hoc network. Ad hoc network

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1 Ad Hoc and Wireless Mesh Networking Laura Marie Feeney Datakommunikation III, HT 00 Overview Ad hoc and wireless mesh networks Ad hoc network (MANet) operates independently of network infrastructure nodes cooperate to provide network services Mesh network supplements network infrastructure nodes cooperate to provide Internet access Ad hoc network mobile wireless network capable of autonomous operation Ad hoc network mobile wireless network capable of autonomous operation operates without base station infrastructure

2 Ad hoc network mobile wireless network capable of autonomous operation Ad hoc network mobile wireless network capable of autonomous operation operates without base station infrastructure operates without base station infrastructure nodes cooperate to provide connectivity nodes cooperate to provide connectivity every node is a router (no default router) Ad hoc network mobile wireless network capable of autonomous operation Ad hoc network mobile wireless network capable of autonomous operation operates without base station infrastructure nodes cooperate to provide connectivity every node is a router (no default router) ad hoc routing problem

3 Ad hoc network mobile wireless network capable of autonomous operation Ad hoc network mobile wireless network capable of autonomous operation operates without centralized administration operates without centralized administration nodes cooperate to provide services Ad hoc network mobile wireless network capable of autonomous operation Ad hoc network mobile wireless network capable of autonomous operation operates without centralized administration operates without centralized administration nodes cooperate to provide services nodes cooperate to provide services address allocation (no DHCP) address allocation (no DHCP) fairness and security

4 Example Example network nodes (mobiles, laptops, PDA s) wireless communication Example Example equivalent topology discover multihop route

5 Example Example route failure due to mobility dynamic route repair Example Example How is a MANET different from other networks? Internet WLAN/Cellular MobileIP extend infrastructure

6 Internet WLAN/celluar Internet routing (+ humans) network provider default router simple default router at edges expertise managing core nodes communicate only with base-station Mobile IP Mobile IP correspondent CN FA CN FA MN home MN HA MobileIP allows a node to change its point of attachment to the network home agent (HA) tunnels traffic to the node

7 Applications Applications Military/rescue (no infrastructure) Military/rescue (no infrastructure) Disaster management (damaged infrastructure) Applications Applications Military/rescue (no infrastructure) Military/rescue (no infrastructure) Disaster management (damaged infrastructure) Disaster management (damaged infrastructure) Spontaneous networks (meeting/conference room) Spontaneous networks (meeting/conference room) Personal area networks

8 Applications Applications Military/rescue (no infrastructure) Extend coverage improve range or capacity in a building Disaster management (damaged infrastructure) Spontaneous networks (meeting/conference room) Personal area networks Campus area networks Applications Applications Extend coverage improve range or capacity in a building Extend coverage improve range or capacity in a building Community mesh networks share network connectivity with neighbors Community mesh networks share network connectivity with neighbors Developing countries provide cheap communication infrastructure

9 History Not a new idea US DARPA (0 s) History Not a new idea US DARPA (0 s) Amateur (ham) radio operators (0 s) packet radio History Not a new idea US DARPA (0 s) Amateur (ham) radio operators (0 s) packet radio renewed interest mid-0 s History Not a new idea US DARPA (0 s) Amateur (ham) radio operators (0 s) packet radio renewed interest mid-0 s IETF MANET working group ()

10 History Not a new idea US DARPA (0 s) Amateur (ham) radio operators (0 s) packet radio renewed interest mid-0 s IETF MANET working group () Ad hoc routing Outline challenges design choices protocol example wireless communication startup companies (000 ) Challenges Challenges distributed state in unreliable environment distributed state in unreliable environment changing topology limited communication capacity limited battery capacity

11 Challenges distributed state in unreliable environment changing topology limited communication capacity limited battery capacity wireless communication variable link quality non-symetric links interference and collisions Criteria effectiveness convergence/recovery scalability (number of nodes, density) Criteria effectiveness convergence/recovery scalability (number of nodes, density) performance data throughput route latency (delay) route optimality (hops/stability/diversity) overhead cost (packets/bandwidth/energy) Alphabet Soup many proposed protocols: AODV CEDAR ABR FSR TORA GSR OLSR LANMAR ZRP LAR DSR OSPF++ RDMAR CBRP DSDV WRP TBRPF CGSR GPSR HSR

12 Design choices protocols divided into a few main categories on-demand (reactive) table driven (proactive) hierarchical/cluster-based geographic/position-based Reactive Routing find routes as needed (on demand) advantages no overhead maintaining unused routes disadvantages high route latency optimization? Proactive routing table-based, more similar to conventional routing advantages low route latency state information disadvantages high overhead (periodic table updates) route accuracy depends on updates AODV (DYMO) Ad hoc On demand Distance Vector Perkins et.al.

13 AODV (DYMO) Ad hoc On demand Distance Vector Perkins et.al. conventional distance vector nodes exchange distance information (to all nodes) with their neighbors periodic exchange and immediate update for changes routing table selects shortest path AODV (DYMO) on-demand variant of conventional distance vector AODV (DYMO) Ad hoc On demand Distance Vector Perkins et.al. conventional distance vector nodes exchange distance information (to all nodes) with their neighbors periodic exchange and immediate update for changes routing table selects shortest path exchange a lot of information that is never used AODV (DYMO) on-demand variant of conventional distance vector route request (RREQ) packet is flooded through the network

14 AODV (DYMO) on-demand variant of conventional distance vector AODV (DYMO) on-demand variant of conventional distance vector route request (RREQ) packet is flooded through the network route request (RREQ) packet is flooded through the network route discovery creates (temporary) reverse paths back to the source route discovery creates (temporary) reverse paths back to the source route reply (RREP) turns a valid reverse path into a route AODV (DYMO) handling topology change AODV (DYMO) handling topology change link failure causes route error (RERR) destination managed sequence number ensures loop freedom

15 AODV (DYMO) AODV (simplified) handling topology change link failure causes route error (RERR) destination managed sequence number ensures loop freedom AODV is RFC (experimental) DYMO is IETF Internet draft 0 route from node to node AODV (RREQ) AODV (RREQ)? hop 0 >: via hop >: via hop >: via hop 0 broadcast flooding of route request wireless multicast advantage node from which RREQ was received defines reverse path to source

16 AODV (RREQ) AODV (RREQ)? hops? hops? hops 0 > (via ) hop > (via ) hop > (via ) hop >: via hop >: via hop > (via ) hop >: via hop 0 RREQ is flooded though the network reverse paths are recorded AODV (RREQ) AODV (RREQ)? hops? 0 hops? hops? hops > (via ) hop > (via ) hop > (via ) hop >: via hop 0 >: via hop > (via ) hop >: via hop >: via hop >: via hop >: via hop unreliable broadcast destination managed sequence number, ID prevent looping reverse paths are recorded

17 AODV (RREQ) AODV (RREQ)? hops 0? hops? hops > (via ) hop > (via ) hop > (via ) hop >: via hop >: via hop > (via ) hop >: via hop 0 >: via hop >: via hop >: via hop > via 0 hop > via 0 hop broadcast collision problem (jitter) reverse paths are recorded AODV (RREQ) AODV (RREQ) 0? hops? hops > (via ) hop > (via ) hop > (via ) hop >: via hop 0 >: via hop >: via hop > (via ) hop >: via hop >: via hop >: via hop > via 0 hop > via 0 hop! hops broadcast flooding is very expensive RREQ arrives at the destination two routes are discovered

18 AODV (RREP) AODV (RREP) 0 0 destination sends unicast RREP (sets sequence number) activate reverse path destination sends unicast RREP (sets sequence number - not shown) AODV (RREP) AODV (RREP) via 0 0 via 0 via RREP messages activates reverse path RREP messages activates reverse path

19 AODV (RREP) AODV (RREP) via via 0 via via via 0 0 via 0 via RREP reaches source route discovery complete source adopts destination sequence number AODV AODV(RERR) via via via 0 via via via 0 0 via 0 via traffic flows along forward route reverse path information times out link failure how to be sure?

20 AODV(RERR) AODV(RERR) via via via via 0 0 via node generates route error message (RERR) forwarded to source AODV(RERR) AODV(RERR)? via 0 0 via 0 initiate new route discovery (RREQ) discover new route (latency)

21 AODV(RERR) AODV(RERR) via via? via 0 via via via 0? 0 via 0 via what about a local repair? initiate RREQ from point of failure what about a local repair? initiate RREQ from point of failure AODV(RERR) AODV(RERR) via via via 0 via 0 via via via 0 via 0 0 via 0 via lower latency lower latency but longer routes

22 AODV(DYMO) (over)-simplified description here further complexities and optimizations AODV-UU implementation is well-known Criteria effectiveness convergence/recovery scalability (number of nodes, density) performance data throughput route latency (delay) route optimality (hops/stability/diversity) overhead cost (packets/bandwidth/energy) OLSR Optimized Link State Routing Clausen et.al OLSR Optimized Link State Routing Clausen et.al conventional link-state routing beacon to determine neighbors for each node, disseminate its links to all other nodes use SPF algorithm to generate routing table

23 OLSR Optimized Link State Routing Clausen et.al conventional link-state routing beacon to determine neighbors for each node, disseminate its links to all other nodes use SPF algorithm to generate routing table high overhead, exchange information for links that are never used OLSR variant of conventional link state routing for each node, disseminate only some of its links for each node, only disseminate information received via some links use SPF to generate routing table OLSR variant of conventional link state routing OLSR variant of conventional link state routing for each node, disseminate only some of its links for each node, only disseminate information received via some links use SPF to generate routing table some links = multipoint selector set

24 OLSR -hop Neighborhood broadcast periodic hello messages IETF RFC (experimental) each message contains a list of neighbors each node discovers its -hop neighborhood discovers failed links discovers bi-directional links Bi-directional Links Bi-directional Links HELLO()={,,,} 0 NBR()={,,,} 0 HELLO()={,,} NBR()={,,,} HELLO()={,,}

25 Multipoint Relay multipoint relay set (MPR): subset of a node s -hop neighbors, such that each of its -hop neighbors is a -hop neighbor of a node in the MPR set Multipoint Relay multipoint relay set (MPR): subset of a node s -hop neighbors, such that each of its -hop neighbors is a -hop neighbor of a node in the MPR set minimum set of -hop neighbors that results in the same set of -hop neighbors Multipoint Relay multipoint relay set (MPR): subset of a node s -hop neighbors, such that each of its -hop neighbors is a -hop neighbor of a node in the MPR set minimum set of -hop neighbors that results in the same set of -hop neighbors each node has an MPR set (not a network MPR set) Multipoint Relay(MPR set) -hop and -hop neighbors of node ode is not needed in the multipoint relay set 0

26 Multipoint Relay(MPR set) Dense Network 0 0 node is not needed in the multipoint relay set with greater node density, the proportion of relay nodes is smaller Dense Network (MPR set) {,} {,} {,} {,} {,} {,,} {,,0} {,0} {,,} {,0} {,} 0 {0} {,0} {0} nodes which are not in the MPR set are in some sense redundant Dense Network (MS set) multipoint selector (MS) set is the inverse of MPR set i.e. nodes that have selected this node as an MPR 0

27 Dense Network (OLSR) Operation: Dense Network (OLSR) Operation: each node uses HELLO messages to find and announce its MPR set Dense Network (OLSR) Operation: each node uses HELLO messages to find and announce its MPR set a node sends link state information only for nodes in its MS set (for which it is an MPR) Dense Network (OLSR) Operation: each node uses HELLO messages to find and announce its MPR set a node sends link state information only for nodes in its MS set (for which it is an MPR) each node computes SPF routes using all received messages

28 Dense Network (OLSR) Operation: each node uses HELLO messages to find and announce its MPR set a node sends link state information only for nodes in its MS set (for which it is an MPR) each node computes SPF routes using all received messages a node only rebroadcasts link state messages from nodes in its MS set OLSR only disseminate link data for green nodes only rebroadcast data from green nodes : : : : : : : 0 : 0 : 0 0: : 0 : 0 : 0 : 0 Criteria effectiveness convergence/recovery scalability (number of nodes, density) performance data throughput route latency (delay) route optimality (hops/stability/diversity) overhead cost (packets/bandwidth/energy)