Mobile IP: Performance

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)

Mobile IP (MIP)

Route Optimization Mobile IP (ROMIP)

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

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

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

Hypothesis (cont) • Direct routing • The source caches the received binding and uses it to tunnel its packets directly to the FA (FA1) • Handover • The 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)

Hypothesis: Time Model for ROMIP

Hypothesis: Fixed Network Topology Macro mobility Micro mobility

Hypothesis: Mobile IP Router Model home list visitor list binding cache routing table

Hypothesis: Mobile host Model

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 descriptors • Average session length (S, in kbit) • Average offered load (L, in kbit/s) • L = S/T, where T is the mean group arrival time

Traffic Pattern

Hypothesis: Mobility pattern • Mobility pattern • Mobility events occur at the arrivals of a Poisson process • When a mobile host enters a new subnet, it stays there for a negative exponential random time • p.d.f. = le-lt , P.D.F. = 1 - e-lt • Descriptor • Average mobility rate (the inverse mean stay time)

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 # session/sec Binding update to HA Binding update to FA # handover during a session W, R, U

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

Theoretical Analysis (cont) • Validation for simulation • Little’s formula: Npkt = lpkt * Tpkt • Npktis the average # of packets in the system (user + control) • lpkt(1/sec) is the overall offered load (user + control) • Tpktis the mean end-to-end packet delay (obtained by weighting user and control delay) • lpkt = L /Plength + R • Plengthis the IP data unit length

Simulation Result- Fig. 9

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 higher than the time needed to transmit a packet over the 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

Discussion- Fig. 9 & 10 (cont) • 3. Increasing the mobility rate, the MIP delay also increases • Owing 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 traffic 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

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 increases • Since longer and longer traffic bursts make HA more congested • 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)

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 improves • Because of direct routing • In MIP, the links surrounding the HA rapidly become choked up by packet trains, giving rise to a huge delay

Simulation Result- Fig. 12 Exchange???

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

Simulation Result- Fig. 13 linear

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

Simulation Result- Fig. 14 For ROMIP

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 delay • A 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

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

Mobile IP: Performance