Mobile IP: Performance

Reference: “Performance evaluation of Mobile IP protocols in a wireless environment”; Dell'Abate, M.; De Marco, M.; Trecordi, V.; Proc. IEEE International Conference on Communications (ICC), 1998; pp. 1810 -1816 (MobileIPUnicast-1.pdf)

2

Mobile IP (MIP)

3

Route Optimization Mobile IP (ROMIP)

4

MIP vs. ROMIP

• Inefficiencies of MIP– Triangle routing

– Home Agent overloading

• Advantages of MIP– Simple

– Exchange of control messages is limited

– Address bindings are highly consistent

5

MIP vs. ROMIP (cont)• Advantages of ROMIP– Direct routing– Handover management

A moving host informs its previous FA about the new care-of-address, so that packets tunneled to the old location can be forwarded to the current location

In MIP, those packets had to be discarded or sent to the HA again

• Disadvantages of ROMIP– Complex

Control messages, processing overhead

– Cached bindings are possibly inconsistent

6

Hypothesis for Simulation• Mobile hosts always obtain a dedicated

bandwidth wireless connection to the currently visited subnet

• Update process model of ROMIP– Binding acquisition

HA, just after having tunneled the 1st packet, sends a binding warning message (W) back to the source

The source, in response to this warning, sends a binding request message (R) to the HA, keeping on sending user packets in the meanwhile

The HA replies with a binding update message (U), containing the requested care-of-address

7

Hypothesis (cont)– Direct routing

The source caches the received binding and uses it to tunnel its packets directly to the FA (FA1)

– HandoverThe destination suddenly moves under another FA

(FA2); just after its movement, it sends two binding update messages (U), both to its HA and to its previous FA (FA1)

The source has no way to get aware of the movement and keeps on emitting user packets to FA1. These packets get lost until FA1 receives the above update

As soon as FA1 gets updated, it warns the source and forwards incoming packets to the actual location (FA2)

8

Hypothesis: Time Model for ROMIP

9

Hypothesis: Fixed Network Topology

Macro m

obility

Micr

o mob

ility

10

Hypothesis: Mobile IP Router Model

home listvisitor listbinding cacherouting table

11

Hypothesis: Mobile host Model

12

Hypothesis: Traffic pattern

• Traffic pattern

– Packet group (geometric r.v.) at each arrival of a Poisson process (Bulking Poisson Process)

– All packets in a group share their destination address, drawn uniformly among all mobile hosts’ addresses

– Two traffic descriptorsAverage session length (S, in kbit)

Average offered load (L, in kbit/s)

L = S/T, where T is the mean group arrival time

13

Traffic Pattern

14

Hypothesis: Mobility pattern

• Mobility pattern

– Mobility events occur at the arrivals of a Poisson processWhen a mobile host enters a new subnet, it stays t

here for a negative exponential random time

p.d.f. = e-t , P.D.F. = 1 - e-t

– DescriptorAverage mobility rate (the inverse mean stay time)

15

Theoretical Analysis• R (packets/s): Rate at which control packets are issued

by ROMIP protocol, normalized for a single user

• Tstay (sec): Mean stay time for a mobile host

• L (kbit/sec): Mean user offered load

• S (kbit): mean session duration

• Bradio (kbit/s) : available one-way bit rate on the radio channel

Binding update to HA Binding update to FA

# session/sec

W, R, U

# handover during a session

16

Theoretical Analysis (cont)

• Discussion

– The control load due to the birth of new sessions decreases by increasing the session length (at a parity of user load, L)

– The control load due to handover events could be brought down by increasing the radio channel capacity (at a parity of user load, L)

– As user load L increases, a proportional control load increase is induced; this reaction does not take place in MIP, for which is simply R = 1/Tstay

17

Theoretical Analysis (cont)• Validation for simulation

– Little’s formula: Npkt = pkt * Tpkt

– Npkt is the average # of packets in the system (user + control)

– pkt (1/sec) is the overall offered load (user + control)

– Tpkt is the mean end-to-end packet delay (obtained by weighting user and control delay)

– pkt = L / Plength + R

– Plength is the IP data unit length

18

Simulation Result- Fig. 9

19

Simulation Result- Fig. 10

20

Discussion- Fig. 9 & 10

– 1. At null mobility rate, end-to-end delay always

increases as session duration increases

– 2. With S = 100 Kbit

The minimum delay is obtained, i.e. a value slightly hi

gher than the time needed to transmit a packet over th

e source and destination radio links (2*8)/19.2

Any further remaining part of a delay rises up to in the

backbone

For null mobility, the above gap ought to be ascribed

only to the increasing traffic burstiness

21

Discussion- Fig. 9 & 10 (cont)

– 3. Increasing the mobility rate, the MIP delay also increasesOwing to network load and tracking effort

– 4. A similar increase is observed for ROMIP too, except for the 400 Kbit session, reason: Suppose that session end-points mobility results in tr

affic scattering in the backbone, thus improving the delay performance over that obtained with lower mobility

With ROMIP, source and destination mobility cuts up the longest sessions into small pieces, thus canceling burstiness effects in the backbone

22

Discussion- Fig. 9 & 10 (cont)

– 5. ROMIP may gain efficiency with longer sessions, because of the source binding acquisition process

– 6. Increasing session length, the MIP delay also increasesSince longer and longer traffic bursts make HA more c

ongested

ROMIP seems to be much less sensible to session duration

However, it is evident that MIP delay performance improves and gets closer to ROMIP’s for relatively short sessions (100 Kbit)

23

Simulation Result- Fig. 11

24

Discussion- Fig. 11– 1. For short sessions, MIP achieves much lower

delay than ROMIP In fact, short sessions hardly enter their direct routing

phase provided by ROMIP

In these condition, ROMIP degenerates and delivers packets by triangle routing;

Moreover, it floods the network with useless control messages, giving rise to a performance drawback

– 2. For longer sessions, ROMIP delay performance improvesBecause of direct routing

In MIP, the links surrounding the HA rapidly become choked up by packet trains, giving rise to a huge delay

25

Simulation Result- Fig. 12

Exchange???

26

Discussion- Fig. 12

– Packet loss

Due to transmissions to the wrong subnet

– Better performance for ROMIP

Because of handover support

But the performance is not substantial

– Loss probability could be reduced by increasing the backbone bandwidth, to allow a more effective tracking of mobile hosts

27

Simulation Result- Fig. 13

linear

28

Discussion- Fig. 13– Right side: cache agent overhead for tunneling

operations

Linear relation between processing load and offered traffic exists, but only for low traffic volumes

– For low mobility and low traffic, left-side diagram

Redirected packets have been tunneled only once (ideal operating region for ROMIP)

– For High traffic

The location tracking algorithm lags behind

On the average, more than one tunnel hop is needed for a packet to catch the destination

29

Simulation Result- Fig. 14

For ROMIP

30

Discussion- Fig. 14

– Impact of cache size over quality of service

– A small cache capacity gives rise to a lower loss and a higher delay

– A large capacity originates a higher loss and a smaller delayA large amount of cached binding may be

inconsistent, but packets succeeding in reaching their destination often travel along the shortest path

– Small lifetimes (timeout values)

May keep the bindings up-to-date, but it is more likely that a valid binding is removed and thus triangle routing occurs

31

Conclusion• MIP shows better performance, when

– The rate of birth and death of sessions is high

• Large session duration

– Exploit the optimization of routing by ROMIP

• As long as the traffic bursts last on average as much as the average cell permanence time

– The direct routing of ROMIP allows to better distribute the traffic offered to the fixed network

– Indirect routing (MIP) is subject to overload of the HA