Subject: [manet] Question regarding QoS Routing in MANETs

From: Faisal Adeem Siddiqui <[email-masked]>
Date: Tue, 10 May 2005 02:31:13 +0900

Dear all,
I have few questions regarding QoS routing in MANETs. Almost all of the QoS routing protocols first reserve the resources on the path according to QoS parameters, and then data transfer takes place. In other cases, the path is selected such that it satisfies the QoS values. If there is no such path available, the connection will be rejected. Now, If the link is broken, a new path will be established in the same fashion. Since MANETs are very dynamic, even though the link is not broken, the link properties such as bandwidth or available data rate can change (decrease) due to increase in interference from other sources etc. Now in this case, it didn't matter if we reserved the resources before or not. Most QoS routing schemes don't have provision for this kind of scenario. One such protocol that monitors link characteristics even after resource reservation and regulate the flows in case of change in QoS parameters is SWAN (Stateless Wireless Ad hoc Network) protocol. SWAN does this by using ECN (Explicit Congestion Notification) field of the IP packet. If there is congestion, intermediate node sets the ECN field of the IP packet. Destination is monitoring the ECN field of all received packets and can regulate the flow if it receives such packets. This causes real-time traffic to re-probe and re-admit. If the resources can't be reserved, the connection will simply be rejected. I wonder why not the source try to re-route the traffic through any other path if resources can't be reserved on the same path again ?
Also I want to know if there is any other such QoS Routing protocol for MANET which does not reserve the resources beforehand or continuously monitor the QoS parameters even after reservation of resources ?

Please correct me if I didn't understand something correctly.

Thanks in advance.
Faisal.

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From: [email-masked]
Date: Mon, 9 May 2005 21:32:06 +0200 (CEST)

Hi Faisal ;==)

> Dear all,
> I have few questions regarding QoS routing in MANETs. Almost all of the
> QoS routing protocols first reserve the resources on the path according to
> QoS parameters, and then data transfer takes place. In other cases, the
> path is selected such that it satisfies the QoS values. If there is no
> such path available, the connection will be rejected. Now, If the link is
> broken, a new path will be established in the same fashion. Since MANETs
> are very dynamic, even though the link is not broken, the link properties
> such as bandwidth or available data rate can change (decrease) due to
> increase in interference from other sources etc. Now in this case, it
> didn't matter if we reserved the resources before or not. Most QoS routing
> schemes don't have provision for this kind of scenario. One such protocol
> that monitors link characteristics even after resource reservation and
> regulate the flows in case of change in QoS parameters is SWAN (Stateless
> Wireless Ad hoc Network) protocol. SWAN does this by using ECN (Explicit
> Congestion Notification) field of the IP packet. If there is congestion,
> intermediate node sets the ECN field of the IP packet. Destination is
> monitoring the ECN field of all received packets and can regulate the flow
> if it receives such packets. This causes real-time traffic to re-probe and
> re-admit. If the resources can't be reserved, the connection will simply
> be rejected. I wonder why not the source try to re-route the traffic
> through any other path if resources can't be reserved on the same path
> again ?
> Also I want to know if there is any other such QoS Routing protocol for
> MANET which does not reserve the resources beforehand or continuously
> monitor the QoS parameters even after reservation of resources ?

We have developped the QOLSR protocol which is an extension introduced to
OLSR to fulfill QoS requirements. It ensures that optimal metrics are made
available along a route between communication partners. Additional fields
about QoS conditions are added to HELLO and TC messages. No additional
control messages are generated. Using QOLSR, a node measures QoS metrics
like available bandwidth, delay, jitter, loss probability, cost, etc., on
links to its neighbor nodes having direct and symmetric link. These QoS
metrics information are used to calculate MPRs and then flooded in the
network by TC messages to calculate routing tables.

Once the path is chosen using multiple constraints distributed algorithms,
QOLSR can achieve end-to-end QoS flow guaranteed without using explicit
reservation mechanisms by applying new distributed solution to the
oscillation, collision of flows, change of topology (current QoS flow
path) and change of QoS conditions problems. The idea is that the first
node in the flow's
current path that precedes the arc problem (an overflowed arc, ...),  and
that has an alternate route satisfying the flow's QoS requirement should
be considered for route switching. You can find more detail in this paper:

[Hakim Badis, Ignacy Gawedzki and Khaldoun Al Agha, "QoS Routing in Ad hoc
Networks Using QOLSR with no Need of Explicit Reservation", in IEEE
VTC'04-Fall: Vehicular Technology Conference, (Los Angeles, USA),
September 2004]. This paper is available in this page http://qolsr.lri.fr/

> Faisal._______________________________________________

Hakim