Download T9-routing

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
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Intro Wlan
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Wlan (Wi-Fi) is IEEE 802.11 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)
802.11 Medium Acess Control (MAC)
802.11 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
one subnet, one ESSID
BSS
Infrastructure or peer-to-’server’
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Nodes can not choose its link, traffic is always
to/from the Access Point (AP)
802.11 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
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WLAN; example of use
Ad-hoc protocols
Two types: proactive and reactive
Different protocols, different features of:
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Scalability, number of nodes
routing table convergence time
organisation
Administration
Resource-usage
Ad-hoc: proactive protocols
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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
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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)
2
originating node
1
3
Two-hop node
5
4
One-hop node
MPR node
MPR(1)={2,3,4,5}
OLSR data structures
MPR relays and multicast control traffic when
theres are topology changes. The receiving nodes use
these TC messages to update the:
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Neighbour sensing information base
Topology information base
Routing table
TC messages are sent from nodes and multicast
by MPRs
Internet connectivity
OLSR
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MANET – Mobile Ad hoc Network
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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)
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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:
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PAA – proactive Auto-configuration
 No use of DHCP, every avoiding point-of-failure.
Client when unconfigured and server when configured.
Why MANET?
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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 ?