An SMR Based Advance Resource Reservation Scheme For Combined Mobility and QoS Provisioning

1. An SMR Based Advance Resource Reservation Scheme For Combined Mobility and QoS Provisioning Hao Wang The University of Edinburgh WP2, Ubiquitous Service

2. Outline • QoS Provisioning in the Mobile Environment • A Session-to-Mobility Ratio Based Advance Resource Reservation Scheme • Performance Comparison • Conclusions

3. QoS Provisioning in the Mobile Environment

4. Resource ReSerVation Protocol (RSVP) • RSVP is a network layer protocol which can be used to reserve resources in the network to guarantee “hard” QoS provisioning. • The simplified procedure: • The sender sends out the PATH messages that includes the traffic profile. • The receiver replies with the RESV messages that reserves the resources along the data path. • Reservation is identified by the IP addresses and port numbers.

5. RSVP in the mobile environment (1/2) • In the mobile environment, the mobile node has to changes its IP address after a network layer (L3) handover. • Therefore, the mobile node has to re-establish the reservation after handover: • for example: Subnet 2 Subnet 1

6. RSVP in the mobile environment (2/2) • This resource re-reservation results in two major problems: • reservation delay: the delay of this reservation may be so long that a delay-sensitive session has to be terminated. • reservation blocking: it is possible that this reservation request is blocked due to the lack of resources in the new subnet.

7. Solutions of the problems in the literature • To reduce the reservation delay: • identify the common part of the old and new data path so that the reservation signalling can be restricted within the affected part of the network • To reduce the reservation blocking probability: • make advance resource reservations in the networks that a mobile node may visit before the handover • The combination of them would be a good approach to provide QoS in the mobile environment.

8. How to make advance reservation (1/3) • There are two major types of advance resource reservation approaches: • Agent-based: uses a special agent to make advance reservation. • Multicast-based: takes advantage of multicast routing protocol. • Agent-based approach: • there is an agent in every subnet which takes charge of resource reservation. • the mobile node makes activereservation in its current subnet. • the mobile node makes passivereservations in its neighbouring subnets. • when the mobile node hands over to a new subnet, it can uses the passive reservation. The active reservation is actively used for communication The passive reservation is not used but only reserved

9. How to make advance reservation (2/3) • Multicast-based schemes: • the current and neighbouring subnets of the mobile node form a multicasting group, and packets are delivered using multicasting routing, i.e., the packets are sent to all the nodes that belong to the group. • similar to the agent-based schemes, the mobile node makes conventionalreservation and predictivereservations in its current and neighbouring subnets respectively. • handover of the mobile node is modelled as leaving and joining the branches of a multicast tree.

10. How to make advance reservation (3/3) • An example showing different types of reservations:

11. Problems of advance resource reservation • Making advance reservations in a subnet increases the blocking probability of new session requests originating from that subnet. • reduces the Grade of Service (GoS) of the network • Since advance reserved resources are not actively used, they waste network resources from the QoS traffic’s perspective. • Proposals that allow traffic with lower QoS level to temporarily borrow the advance reservations is not reliable. • Only allowing best-effort traffic to use the passive reservations wastes network resources from the QoS traffic’s perspective.

12. Our solution • Integrate the call admission control (CAC) mechanisms into the advance resource reservation scheme so that the network resource utilisation is improved.

13. A Session-to-Mobility Ratio Based Advance Resource Reservation Scheme

14. Motivation and approach • Motivation: • to design a scheme which can balance the amount of active reservations (requested by local mobile nodes) and passive reservations (requested by foreign mobile nodes) in a subnet. • Approach: two CAC mechanisms • Passive reservation bounding • SMR based replacement • Modularity: • The detailed signalling procedure is left open and the scheme can be regarded as a building block of the proposals that combine MM and QoS

15. Passive reservation bounding (1/2) • Aim: • to restrict the amount of passive reservations in a subnet. • We give a higher priority to active reservations by setting aside resources (e.g. channels) just for them. • Therefore, there are two types of channels: • dedicated channels: for only active reservations • standard channels: for passive reservations and for active reservations when there is no free dedicated channel

16. Passive reservation bounding (2/2) • Needs the help of the bandwidth broker (BB) in each subnet which takes charge of allocating channels according to the type of requests: • active reservation –> dedicated or standard channel • passive reservation –> standard channel • To avoid over-restricting passive reservation, the BB should try to assign an active reservation to a dedicated channel first, and then to a standard channel if no free dedicated channel is available. • Assume the total number of channels in a subnet is N and there are S standard channels, then • the maximum number of passive reservations is S, and • at least N-S active reservations can be accepted

17. SMR based replacement (1/2) • Aim: • to efficiently utilise the standard channels of a subnet since they are scarce resources from the viewpoint of the foreign mobile nodes. • The mobile nodes who are most likely to handover during the session are the most eligible to make passive reservations. • This probability can be reflected in the ratio of session duration to subnet residence time, i.e., the session-to-mobility ratio (SMR).

18. SMR based replacement (2/2) • The replacement procedure works as follows: • If the BB receives a passive reservation request and finds out there is no free standard channel available, then: • The BB compares the SMR value of the requesting foreign mobile node (SMR_request) and the smallest of the SMRs of the foreign mobile nodes that have already acquired standard channels (SMR_smallest). • If SMR_request > SMR_smallest, then the standard channel is re-allocated to the requesting mobile node. • Otherwise, the passive reservation request is rejected.

19. Flow chart of the SMR based advance resource reservation scheme

20. About the traffic type • In our work, the QoS sessions are assumed to be of the same type. Therefore, a mobile node is more eligible in the sense that it has a larger SMR value. • However, in a broader sense, the type of the QoS sessions should be considered and it is an important criterion for determining which mobile node is more suitable for making passive reservations. • Admission control according to different types of traffic can be implemented in the “policy control” module defined in the RSVP protocol.

21. About the scheme • Although the advance resource reservation scheme looks similar to the handover prioritised scheme used in the cellular networks, they are different majorly in the ways in which resource are reserved. • In handover prioritised schemes, reserved resources can be used by anyone. • In advance resource reservation schemes, resources are reserved exclusively and so network utilisation is deteriorated. • The side effects of the scalability problem of RSVP can be reduced by RSVP aggregation techniques (e.g. RFC 3175).

22. Performance Comparison

23. Assumptions in the PEPA models • Traffic Model: • Two-phase hyper exponential (2P-HE) distribution for session duration: • 2P-HE is validated by both simulation and experimental measurements • Mobility Model • Exponential distribution for the subnet residence time • What determines the handover behaviour: • cell shape • movement pattern • type of handover • No proven probability distribution exists.

24. Performance metrics • We investigate the congestion level of the network form the viewpoint of different types of reservations, i.e., • Active reservation blocking probability • Passive reservation blocking probability • Tuning parameters are traffic intensity: • session arrival rate • session holding time

25. Active reservation blocking prob. vs. session arrival rate (mean session holding time = 400s) SMR based scheme is better because it sets aside dedicated channels for active reservations

26. Active reservation blocking prob. vs. session holding time (mean session arrival interval = 180s)

27. Passive reservation blocking prob. vs. session arrival rate (mean session holding time = 400s) SMR based scheme is better when the traffic intensity is high due to bounded resources for passive reservations

28. Passive reservation blocking prob. vs. session holding time (mean session arrival interval = 180s)

29. Discussion (1/2) • The reason why SMR based scheme performs better is because it • sets aside dedicated resources for active reservations • only allows eligible foreign mobile nodes to make passive reservations. • The expense of the SMR based scheme is that • slow mobile nodes have to make reservation requests after handover

30. Discussion (2/2) • However, the SMR based scheme is still reasonable because: • Blocking passive reservations has no effect on the foreign mobile node’s ongoing session since it is not actively used, while an active reservation implies there is a local mobile node that really needs it. • When the foreign mobile node without advance reservation hands over into the local subnet, its reservation request is an active one which will benefit from the passive reservation bounding. • The passive reservation brings no revenue whilst active reservation does.

31. Conclusions

32. In conclusion • The SMR based advance resource reservation scheme can efficiently reduce both active and passive reservation blocking probabilities. • The enhancements are achieved by the means of: • setting aside dedicated channels for active reservations, and • only allowing mobile nodes with large SMR values to make passive reservations.

33. For further information please contact: Hao Wang E-mail: h.wang@ed.ac.uk