routing across wired and wireless mesh networks experimental compound internetworking with ospf juan...
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Routing across wired and wireless mesh networks
Experimental compound internetworking with OSPF
Juan Antonio Cordero Matthias Philipp Emmanuel Baccelli
INRIA Saclay – Île-de-France (France)
8th International Wireless Communications and Mobile Computing Conference
Limassol (Cyprus), August 27-31, 2012
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Agenda
Motivation: compound internetworks in the Internet core
Introduction to OSPF
Our contribution: objectives and experiments
The testbed
Data plane results
Control plane results
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‘Compound’ internetworks in the Internet
Set of interconnected wireless and wired networks in a single domain
Autonomous System
Rest of the Internet
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‘Compound’ internetworks in the Internet
Set of interconnected wireless and wired networks in a single domain
Compound Autonomous System
Rest of the Internet
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OSPF basic operation
What is OSPF ?
“Open Shortest Path First”
Link-state routing protocol
Main Interior Gateway Protocol (IGP) used in Internet routing
How does it work ?
Interface types
(Supported networks) Point-to-point Broadcast
MANET-like
Packet types
Neighbor sensing : Hellos
Topology flooding : LS-Updates , LS-Acks
Database sychronization : LS-Reqs , DB Description
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Contribution : Objectives and Experiments
Experimental evaluation in a compound internetworking testbed (layer 3 perspective) Confirm/dismiss underlying assumptions on previous research
On the data plane : UDP flows and pings
On the control plane : OSPF control traffic structure
Extension of OSPF for operation in compound internetworks
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Wired/wireless static internetwork, 6 computers
MAC layer : 802.3 Ethernet (wired)802.11b WLAN (wireless)
Routing : OSPF for IPv6 point-to-point interface (wired)MPR-OSPF MANET interface (wireless)
3 with wired interfaces (DECchip 21140)3 with wireless interfaces (Broadcom BCM4306 WLAN)
2 with wired and wless interfaces (hybrids)
Testbed description
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Study of control traffic
eth0
eth0 S
h2
w2
eth1
eth0
wlan0 wlan0
wlan0 wlan0
h2
w2
eth0
eth0 eth1
eth0
wlan0 wlan0
wlan0 wlan0
wlan0
h1
eth0
eth0 eth1
eth0
wlan0
wlan0 wlan0
wlan0
h1
w3
1 wired hop + 1 wireless hop 1 + 2 1 + 3
S
h1
w1
w3
S
h2
w2w1
w3
Logical topologies : three scenarios
Scenario I Scenario II Scenario III
Data flow (UDP/ICMP)
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Computers’ position at the Computer Science Lab of École Polytechnique (LIX, France)
Sh1
h2 w2
w1
w3
w3
PC with wired ifs.
PC with (only) wless ifs.
Physical topology
10 m
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Quality of communication degrades (almost) linearly as packets traverse more wireless hops
Packet Delivery Ratio (/1)
Data plane results
Round Trip Time (msec)
UDP data flows ICMP requests (pings)
m ~ -15%
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Control plane results : wireless/wired comparison
hybrid1:eth1 hybrid1:wlan0
Periodic pattern in both cases
Different role of flooding in wireless and wired components
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Control plane results : OSPF control traffic in wireless
wless3:wlan0
Synchronization traffic is present during the whole lifetime of a wireless (static) link
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To conclude
Routing with OSPF in compound (wired/wireless) internetworks
OSPF optimization for wireless mesh operation
Link-state synchronization traffic to be minimized Flooding bursts to be avoided
General observations
Number of wireless links in ‘compound’ routes should be minimized ‘Optimal’ compound routes are not necessarily those with less hops
Metrics for wireless networks Integrated shortest-path routing for compound internetworks
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Backup slides
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Compound Autonomous Systems
Compound Autonomous System
Rest of the Internet
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Testbed configuration details
CBR UDP trafficSender bit rate: 100 pkt/secPacket payload: 1024 BCBR real effective traffic rate ~ 300 kbpsFlow duration: 5 min/flow60 iterations/value
ICMP traffic84 iterations/value
OSPF parameters (common for wired/wireless interfaces, for fairness)HelloInterval: 2 secDeadInterval: 10 secRxmtInterval: 5 secAckInterval: 2 secMinLSInterval: 5 secMinLSArrival: 1 secLSRefreshInterval: 60 sec
Other parametersIEEE 802.11b: 11 Mbps (nominal data rate), no RTS/CTS, ARQIP MTU: 1500 B
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Sh1
h2 w2
w1
w3
w3
PC with wired ifs.
PC with (only) wless ifs.
Physical topology : routes for data flows
10 m
2 hops = 1 + 1
3 h. = 1 + 2
4 h. = 1 + 3
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Link-state routing
Link-State Advertisements(LSAs)
Link-state Database(LSDB)
Shortest Path Tree(SPT)
Routing Table
( Dijkstra ) ( next-hop )