Chapter 4 Network-based Distributed Mobility Management for Network Mobility:
4.6 Simulation Evaluation in ns-2
4.6.1 Simulation Scenario in ns-2
This section discusses the simulation performed using ns-2 [66] with the NIST mobility package for PMIPv6 [67]. The simulator has been used to model NDM-RMG and NEMO basic support protocol (NBSP). Figure 4-10 demonstrates the topology used in the simulation with two levels of nesting. The configuration parameters used in the simulation are shown in the figure. Routers (router1, router2 and router3) are fixed routers, which emulate the mobile routers. They emulate the nesting configuration.
In Figure 4-10, the correspondent node (CN) is a constant bit rate (CBR) UDP source. The CN is configured to send to MNN3 (a sink node) data with a packet size of 1000 bytes generated at packet intervals of 0.01sec.
The link between routers emulates a wireless link (IEEE 802.11b) with link delay and bandwidth shown in the figure.
router0 AR/MAG router1 router2 router3 sink node(MNN3) CBR UDP source (CN) Delay : 10ms Bw: 100Mbps Delay : 10ms Bw : 100Mbps HA3/RM3 HA2/RM2 HA1/RM1 Delay : 10ms Bw: 100 Mbps Delay : 5ms Bw: 100Mbps Delay : 2ms Bw: 100Mbps Delay : 2ms Bw: 11Mbps Delay : 2ms Bw: 11Mbps Delay : 2ms Bw: 11Mbps Delay : 2ms Bw: 11Mbps
Figure 4-10 Simulated nested NEMO topology
evaluated and compared in terms of packet delivery latency and packet overhead over the wireless link. The impacts of the number of levels of nesting and the distance between HAs/RMs on packet delivery latency and packet overhead are analysed.
4.6.2 Simulation Results and Analysis
Figure 4-11 shows a variation of the packet delivery delay for the packets sent to a node at the mth level of nesting (sink node [MNN3]), according to the number of levels of nesting. It compares the NDM-RMG and the NBSP schemes. The number of levels of nesting is varied from 0 to 4 (0 implies that a mobile network has moved to a visited network, but no nesting is formed). The delays between HAs/RMs are fixed at 20ms. Whereas the packet delivery delay of the NBSP scheme is significantly affected by the level of nesting, it can be seen that the packet delivery delay for NDM-RMG scheme is only slightly affected by the level of nesting. Thus, the NDM-RMG scheme addresses the pinball routing problem because it uses distributed mobility management functions and a routing optimization mechanism.
Figure 4-11 The impact of the number of levels nesting on Packet delivery delay
Figure 4-12 shows the impact of the distance between the HAs/RMs on end-to-end delay of the two schemes. During simulation, the number of levels of nesting has been set to 4; and the distance between the HAs/RMs has been varied between 10ms and 100ms. The packet delivery latency for the packets sent from the CN to the MNN3 has been measured. The results show that the packet delivery latency increases as the distance between HAs/RMs increases – for both
0 20 40 60 80 100 120 140 0 1 2 3 4 en d -to -en d la ten cy (m s)
number of level of nesting
NDM-RMG NBSP
schemes. However, the NDM-RMG scheme experiences only a slight increase in terms of packet delivery latency, as the distance between the HAs/RMs increases; whereas the NBSP scheme experiences a significant increase in the packet delivery latency. This is because the NDM-RMG scheme optimizes the data route; and it is therefore, less affected by the pinball routing problem.
Figure 4-12 End-to-end delay, according to the distance between HAs/RMs
Figure 4-13 shows the data packet size transmitted from the CN and the measured packet size at the top-level mobile router (a size of the packet received at router 1), as the number of levels of nesting is varied during the simulation. The number of levels of nesting has been varied from 0 to 4. It can be seen from the figure that the size of the packet for NBSP increases as the level of nesting increases. This is because of the encapsulation due to pinball routing, which adds an extra header to the packets. As a result, the extra header of the packet is pushed to wireless link, which consumes the wireless link resources unnecessarily. In contrast, the NDM-RMG scheme has no packet overhead over the wireless link due to network-based feature used in the design of the scheme.
0 100 200 300 400 500 600 10 20 30 40 50 60 70 80 90 100 en d -to -e n d la ta nc y (ms )
distance between HAs/RMs (ms) NDM-RMG
Figure 4-13 Measured packet size in the wireless link
4.7 Summary
The chapter has presented novel network-based distributed schemes for both non-nested and nested NEMO scenarios, which are named NDM-RMGs. The schemes decompose the LMA entity in PMIPv6, and distribute the mobility routing function to the gateways of different networks. The schemes combine this distribution with a delegating router function co-located with the location manager and the mobile routers, which helps to solve the pinball routing problem in the standard NEMO Basic Support protocol.
The detailed functioning of the scheme has been discussed, with signalling diagrams. The performance analysis shows that NDM-RMG mitigates the packet header overhead. The results also show that NDM-RMG scheme reduces packet delivery latency, PDC, and BuC – when compared with the NBSP scheme. Although, N-DMM has a slightly smaller packet delivery delay, PDC and BuC in cases where the mobile nodes are close to traffic anchoring networks, NDM-RMG outperforms N-DMM, when the mobile network moves far away from the anchoring network. The NDM-RMG is network-based DMM schemes; whereas N-DMM is a host-based DMM scheme. Thus, the N-DMM scheme inherits most of the shortfalls of host- based mobility support.
900 950 1000 1050 1100 1150 1200 1250 0 1 2 3 4 p a ck et z is e (b y te)
number of level of nesting
pkt tran. by CN
pkt recvd at TMR (NDM-RMG) pkt recvd at TMR (NBSP)