Problem Statement for OSPF
Extensions for Mobile Ad Hoc
Routing
Fred Baker
Cisco Systems
draft-baker-manet-ospf-problemstatement-00.txt
Interesting drafts
• Things we think are close:
– draft-mirtorabi-ospfv3-af-alt-00.txt
– 3 more drafts coming
• Related Work
– draft-ogier-manet-ospf-extension-00.txt
– draft-spagnolo-manet-ospf-wireless-interface00.txt
Fundamental Approach
• Current target:
– US Army WIN-T Network
• Design Guidelines
– Add a radio interface to OSPF without perturbing
existing protocol or capabilities
– Using that within a combined radio+wired network
• Collaboration between
–
–
–
–
Cisco folks
Inria (OLSR) folks
Boeing Research
Naval Research Labs
Security considerations
• Mobile wireless networks prone to physical
security threats
• Inter-router authentication needed prior to
the exchange of network control
information.
Network design requirements
• Manet networks are not often isolated networks
• Manet networks often consist of vehicles
containing racks with equipment and an internal
LAN, or vehicles or robots accompanying groups
of people connected to them via wireless LAN
technologies and interconnected with other such
groups.
• Often interspersed with field offices
• Connected to a larger internet via standard WAN
technologies such as satellite links, optical fiber,
or virtual and circuit switched networks.
Combining manet and traditional
wired networks
• Adaptation of both OSPFv2 and OSPFv3
has been considered
The big picture
Service backbone
Such as satcom to
Manet cloud
Fixed assets
Truck addressable
Within regional rapid
Deployment network
Unit-specific
Fixed assets
Truck addressable
Within fixed base
Network (802.11)
NIPRNET
etc
Base network
Router-to-radio connection
System
Next-generation
3200
Radio
Different rates depending on SNR/BER and
radio waveform of connection
(potentially many waveforms in same chassis)
Key considerations in traffic
management
• Router-radio interface has
what amounts to virtual
circuits per neighbor
–Shallow txring in radio per
routing neighbor
–Separate MQC QoS data
structures per routing
neighbor
–Each routing neighbor has a
different rate, managed by
the radio
–Therefore each neighbor
must have its own controlled
rate protocol between router
and radio
System
PPPOE with
extensions
Next-generation
3200
JTRS Radio
Mobile ad hoc network issues
•
•
•
•
Often bandwidth-constrained
Often power-constrained
Limited security
Unnecessary transmission is something to
be avoided.
• Security threats need to be actively
addressed,
• Transmissions and computation loads
need to be minimized.
Ad hoc networks
• IEEE 802.11?
• Choose layer 3 routing over 802.1
bridging?
– Network management concerns,
– Scaling concerns,
– Administrative boundaries
• No obvious way to aggregate neighbor
sets in the way one does for lans.
Relay traffic minimization
• Optimizations such as DR election will not
perform correctly in MANET networks
• How much information needs to be
flooded throughout the network?
– Ideal solution: each node will receive a
particular lsa exactly once
– It would be nice if only and exactly one router
relayed lsas.
– It would be nice to minimize the transmission
of lsa acknowledgements
Standard OSPF Flooding
Overlapping Relays
Addressing power issues
• Units that rely on batteries may set a policy that
they are willing to relay messages on their radio
interfaces, but not very willing
• May also have LAN interfaces and be willing to
relay traffic from radio interfaces on which they
are not exchanging even keep-alive traffic to
non-radio neighbors at times that their radio
interfaces are incommunicado.
Scaling for rapid movement
• Network should not thrash
• If neighbor relationships are changing rapidly,
the time invested to become FULL with a peer
as defined in OSPF must be minimized,
• Efficiently scope the propagation of topology
information such that rapid mobility or change in
one part of the network need not be
disseminated throughout the network.
IPv4 and IPv6 routing
• OSPF has historically chosen a "ships in the
night" model
• In mobile ad hoc networks, however, running
two protocols in parallel has a heavy impact
when the network changes
• In mobile ad hoc networks carrying both ipv4
and ipv6 traffic, it would be good for a single
routing protocol to calculate one set of routes
and decorate those routes with both ipv4 and
ipv6 prefixes.
Reliable vs unreliable flooding
• Problem with unreliable flooding: the
assumptions it makes.
– Frequent unreliable flooding: limited scalability
• Consequences of losing even a single LSA can be
great.
– Exponential explosions of transmissions, such
as can be prohibitively chatty
Area hierarchy
• No present manet protocol provides a
counterpart to OSPF administrative areas.
• Some provide dynamic clustering
• Not obvious that the hierarchical area
model fits proposed manet deployments.
• Model permitting summary lsas exchange
at any boundary preferable
Problem Statement for
OSPF Extensions for
Mobile Ad Hoc Routing
Fred Baker
Cisco Systems
draft-baker-manet-OSPFproblem-statement-00