Routing Protocols in Ad-hoc Networks, OLSR Self configuring systems (SCS) TTM3 – Høst 2004 Jørn Andre Berntzen 22/10/2004

Overview Intro to wlan Type of Wlans Example of usages Example protocol Relevance to SCS

Intro Wlan Wlan (Wi-Fi) is IEEE standard Wlan is a Wireless LAN Alternative to cabled LAN Radio interface, either send or receive 2.4 Ghz free (microwave & bluetooth) 5.15–5.35 GHz free for indoor usage in Norway campus, school, airports (hotspot)

Medium Acess Control (MAC) is a protocol for communication between two nodes ( one-hop )

Two types of Wlan Infrastructure: One master, several slaves Ad-hoc: All potential masters and slaves at the same time IBSS

More of infrastructure BSS one subnet, one ESSID

Infrastructure or peer-to-’server’ Nodes can not choose its link, traffic is always to/from the Access Point (AP) says CSMA/CA (PCF) Hotspots x APs acts between at least two wireless nodes APs in a ESS supports up to 255 nodes (one subnet) Solution is centralized and scalable Often used solution today (2004)

Example Ad-hoc ’without’ protocol P2P type,one-hop only (802.11)

Ad-hoc ’with’ protocol (routing) -multihop-

Ad-hoc with protocols, selfconfiguring Self-organized routing (multihop) Dynamic updating and rapid topology changes as nodes come and go No default gateway, a problem really Good for emergencies – redundancy in every node reachable

WLAN; example of use

Ad-hoc protocols Two types: proactive and reactive Different protocols, different features of: Scalability, number of nodes routing table convergence time organisation Administration Resource-usage

Ad-hoc: proactive protocols Updates routing table proactively – before route really needs to be know Frequent update of routing table gives more overhead to network traffic But only short delay when packets need to be transferred Scalable if zoned or nodes given different roles

Ad-hoc: reactive Protocols Updates routes only when data is to be transferred Updating routing table gives small overhead to traffic Updating typically done with controlled ’flooding requests’ into the net Possible long delay for packet transmission if entry in routing-table has timed-out

Optimized link source routing (OLSR) Type: Proactive and ad-hoc Mobile Ad Hoc Network Protocol (MANET) Routing: Link state routing protocol w/optimization Uses: Multipoint relay (MPR) Two-hop node One-hop node MPR node originating node MPR(1)={2,3,4,5}

OLSR data structures Neighbour sensing information base Topology information base Routing table TC messages are sent from nodes and multicast by MPRs MPR relays and multicast control traffic when theres are topology changes. The receiving nodes use these TC messages to update the:

Internet connectivity OLSR MANET – Mobile Ad hoc Network OLSR ’Internet Connectivity’  Auxiliary function of OLSR  Uses Host and Network Association (HNA) messages  injecting external routing information into an MANET

OLSR Plugins (the Unik Olsrd) Add-ons to the original OLSR  Plugin uses the ’standard’ OLSR forwarding  No need to change implemented code, patch e.g  Self-configuring nodes Example of plugin:  PAA – proactive Auto-configuration  No use of DHCP, every avoiding point-of-failure. Client when unconfigured and server when configured.

Why MANET? No centralized administration mobile-user friendly (PDA, laptop) Self-creating, self organizing Anytime, anywhere No fixed topology Fault resilient Wireless extension to the Internet Protocol (IP)

Questions ?