Mobile Ad Hoc Network (MANET) PERTEMUAN KESEMBILAN

Jaringan Wireless secara umum:  Jaringan Wireless umumnya bekerja berdasarkan salah satu topology konfigurasi baik jaringan Ad-Hoc ataupun jaringan Infrastructure.

Topologi pada Jaringan terdiri dari 1. Topologi Ad-Hoc 2. Topologi Infrastruktur

Topologi Ad-Hoc  Jaringan wireless Ad hoc adalah kumpulan node (atau router) wireless mobile yang secara dinamis keberadaannya tanpa menggunakan jaringan infrastruktur yang ada atau administrasi yang terpusat.  Jaringan wireless Ad Hoc dapat juga dikatakan sebagai desentraslisasi jaringan wireless.  Jaringan ad-hoc merupakan bentuk komunikasi jaringan wireless yang paling sederhana.

Topologi Ad-Hoc (2)  Pada jaringan Ad Hoc, router dapat dengan bebas melakukan organiasi jaringan yang berakibat topologi akan berubah dengan cepat dan sulit untuk diprediksi. Dengan fitur ini, jaringan Ad Hoc mengalami beberapa tantangan antara lain, Multihop Mobility Kombinasi jaringan yang besar dengan berbagai peralatan yang berbeda Bandwidth Keterbatasan konsumsi battery

Topologi Ad-Hoc (3)  jaringan Ad Hoc juga memerlukan protokol routing karena setiap node memerlukan pertukaran data.  Berbeda dengan jaringan infrastruktur, jaringan ad-hoc tidak membutuhkan sebuah wireless LAN untuk menghubungkan masing-masing komputer dan topologi jaringan yang terbentuk adalah jaringan mesh.

Topologi Ad-Hoc (4)  Berikut adalah beberapa keuntungan dari sebuah jaringan wireless ad-hoc: 1. Jaringan wireless Ad-Hoc sangat sederhana dalam men- setup nya. Tancapkan adapter wireless ke pada laptop / computer, configure softwarenya, dan andapun sudah bisa melakukan komunikasi antar laptop 2. Jaringan Ad-Hoc adalah murah karena anda tidak memerlukan sebuah wireless access point. 3. Jaringan Ad-Hoc adalah cepat. Rate throughputnya antar adapter dua kali lebih cepat daripada anda menggunakan wireless access point dalam topology infrastcruture.

Topologi Infrastruktur konsep jaringan infrastruktur dimana untuk membangun jaringan ini diperlukan wireless LAN sebagai pusat. Wireless LAN memiliki SSID (Service Set Identifier) sebagai nama jaringan wireless tersebut, dengan adanya SSID maka wireless LAN itu dapat dikenali. Pada saat beberapa komputer terhubung dengan SSID yang sama, maka terbentuklah sebuah jaringan infrastruktur. terlihat bahwa beberapa komuputer dihubungkan oleh satu wireless lan, disini toplogi jaringan yang terbentuk adalah topologi star.

Topologi Infrastruktur (2) Dengan jaringan topology Infrastcruture memungkinkan anda untuk: 1. Terhubung kepada jaringan kabel LAN. Sebuah wireless access point memungkinkan anda memperluas Jaringan LAN anda dengan kemampuan koneksi secara wireless. 2. Komputer pada jaringan kabel dan komputer dengan koneksi wireless bisa saling berkomunikasi satu sama lain. Hal ini lah yang menjadi kekuatan utama dari topology wireless infrastructure. 3. Memperluas jangkauan wireless anda. Dengan jalan meletakkan sebuah wireless access point diantara dua wireless adapters memperpanjang jangkauan menjadi dua kali lipat.

Topologi Infrastruktur (4) 4.Menggunakan kemampuan roaming. Jika anda menggunakan beberapa wireless access point seperti halnya dalam sebuah kantor yang besar atau rumah yang sangat luas, user bisa melakukan roaming antara dua cell access point yang saling terikat, tanpa harus kehilangan koneksi kepada jaringan walau melompat dari satu access point ke access point lainnya. Modus dari wireless access point dengan kemampuan roaming seperti ini disebut WDS (Wireless distribution system) 5.Dengan infrastructure topology, anda bisa berbagi sambungan internet. Mungkin perangkat yang sangat praktis untuk berbagi sambungan internet broadband dari sambungan ADSL adalah wireless modem-router

 Mobile Ad Hoc Network (MANET) indicates a wireless network of mobile nodes that have no fixed routers.  The nodes in this network also serve as routers that are responsible for finding and dealing with the route to every node in the network.  Some characteristics of MANET are: dynamic network configuration, limited bandwidth power constraints for each operation, low overheads, and an adaptive system able to handle packet loss.  The MANET network layer has two parts, namely the network layer and the transport layer.  In the network layer of MANET is the IP (Internet protocol) and the ad hoc routing layer uses the AODV protocol (ad hoc on demand distance vector)

Mobile ad hoc networks  Standard Mobile IP needs an infrastructure  Home Agent/Foreign Agent in the fixed network  DNS, routing etc. are not designed for mobility  Sometimes there is no infrastructure!  remote areas, ad-hoc meetings, disaster areas  cost can also be an argument against an infrastructure!  Main topic: routing  no default router available  every node should be able to forward

Solution: Wireless ad-hoc networks  Network without infrastructure Use components of participants for networking  Examples Single-hop: All partners max. one hop apart Bluetooth piconet, PDAs in a room, gaming devices…  Multi-hop: Cover larger distances, circumvent obstacles Bluetooth scatternet, TETRA police network, car-to-car networks… Internet: MANET (Mobile Ad-hoc Networking) group

Manet: Mobile Ad-hoc Networking

Problem No. 1: Routing Highly dynamic network topology  Device mobility plus varying channel quality  Separation and merging of networks possible  Asymmetric connections possible

Traditional routing algorithms Distance Vector  Periodic exchange of messages with all physical neighbors that contain information about who can be reached at what distance  Selection of the shortest path if several paths available  Every node maintains the distance of each destination Link State  Periodic notification of all routers about the current state of all physical links  Router get a complete picture of the network  Each node maintains a view of the network topology Example  ARPA packet radio network (1973), DV-Routing  every 7.5s exchange of routing tables including link quality  updating of tables also by reception of packets  routing problems solved with limited flooding

Distance-Vector  Known also as Distributed Bellman-Ford or RIP (Routing Information Protocol)  Every node maintains a routing table  all available destinations  the next node to reach to destination  the number of hops to reach the destination  Periodically send table to all neighbors to maintain topology

Distance Vector (Tables) C Dest.NextMetric… AA1 BB0 CC2 Dest.NextMetric… AA0 BB1 CB3 12 Dest.NextMetric… AB3 BB2 CC0 BA

(A, 1) (B, 0) (C, 1) (A, 1) (B, 0) (C, 1) Distance Vector (Update) C Dest.NextMetric… AA1 BB0 CC1 Dest.NextMetric… AA0 BB1 CB Dest.NextMetric… AB3 2 BB1 CC0 BA B broadcasts the new routing information to his neighbors Routing table is updated

(D, 0) (A, 2) (B, 1) (C, 0) (D, 1) (A, 1) (B, 0) (C, 1) (D, 2) Distance Vector (New Node) C 11 BAD 1 broadcasts to update tables of C, B, A with new entry for D Dest.NextMetric… AB2 BB1 CC0 DD1 Dest.NextMetric… AA1 BB0 CC1 DC2 Dest.NextMetric… AA0 BB1 CB2 DB3

Link-State  Like the shortest-path computation method  Each node maintains a view of the network topology with a cost for each link  Periodically broadcast link costs to its outgoing links to all other nodes such as flooding

Link-State E B D G H F A C link costs

Routing in ad-hoc networks  The big topic in many research projects  Far more than 50 different proposals exist  The most simplest one: Flooding!  Flooding is a simple routing technique in computer networks where a source or node sends packets through every outgoing link.  Flooding, which is similar to broadcasting, occurs when source packets (without routing data) are transmitted to all attached network nodes.  Because flooding uses every path in the network, the shortest path is also used. The flooding algorithm is easy to implement.

Problems of traditional routing algorithms Dynamic of the topology frequent changes of connections, connection quality, participants Limited performance of mobile systems  periodic updates of routing tables need energy without contributing to the transmission of user data, sleep modes difficult to realize  limited bandwidth of the system is reduced even more due to the exchange of routing information  links can be asymmetric, i.e., they can have a direction dependent transmission quality

Types of routing  Flat Proactive Routing  Link state Fish-Eye Routing, GSR, OLSR.  Table driven: Destination-Sequenced Distance Vector ( DSDV), WRP)  On-Demand or Reactive Routing  Ad hoc On-demand Distant Vector (AODV)  Dynamic Source Routing (DSR)  Hybrid Schemes  Zone Routing ZRP, SHARP (proactive near, reactive long distance)  Safari (reactive near, proactive long distance)  Geographical Routing  Hierarchical: One or many levels of hierarchy  Routing with dynamic address  Dynamic Address RouTing (DART)

Proactive Protocols  Proactive: maintain routing information independently of need for communication  Update messages send throughout the network periodically or when network topology changes.  Low latency, suitable for real-time traffic  Bandwidth might get wasted due to periodic updates  They maintain O(N) state per node, N = #nodes

On-Demand or Reactive Routing  Reactive: discover route only when you need it  Saves energy and bandwidth during inactivity  Can be bursty -> congestion during high activity  Significant delay might occur as a result of route discovery  Good for light loads, collapse in large loads

Hybrid Routing  Proactive for neighborhood, Reactive for far away (Zone Routing Protocol, Haas group)  Proactive for long distance, Reactive for neighborhood (Safari)  Attempts to strike balance between the two

Hierarchical Routing  Nodes are organized in clusters  Cluster head “controls” cluster  Trade off  Overhead and confusion for leader election  Scalability: intra-cluster vs intercluster  One or Multiple levels of hierarchy

Geographical Routing  Nodes know their geo coordinates (GPS)  Route to move packet closer to end point  Protocols DREAM, GPSR, LAR  Propagate geo info by flooding (decrease frequency for long distances)

Proactive: DSDV - Destination- Sequenced Distance Vector Algorithm  By Perkins and Bhagvat  Based on Bellman Ford algorithm  Exchange of routing tables  Routing table: the way to the destination, cost  Every node knows “where” everybody else is  Thus routing table O(N)  Each node advertises its position  Sequence number to avoid loops  Maintain fresh routes

DSDV details  Routes are broadcasted from the “receiver”  Nodes announce their presence: advertisements  Each broadcast has  Destination address: originator  No of hops  Sequence number of broadcast  The route with the most recent sequence is used

Dynamic source routing II

A B C E D G H F A A A-B A-C A-C-E A-B-DA-B-D-G Route Discovery A-B-C Route Request (RREQ) Route Reply (RREP) Route Discovery is issued with exponential back-off intervals. Initiator ID Initiator seq# Target ID Partial route RREQ FORMAT

Route Discovery: at source A A need to send to G Lookup Cache for route A to G Route found ? Start Route Discovery Protocol Continue normal processing Route Discovery finished Packet in buffer? Send packet to next-hop done Buffer packet no Write route in packet header yes no wait

DSR: Route Discovery

Dynamic source routing III

Route Maintenance  Route maintenance performed only while route is in use  Error detection:  Monitors the validity of existing routes by passively listening to data packets transmitted at neighboring nodes  Lower level acknowledgements Route Error  When problem detected, send Route Error packet to original sender to perform new route discovery  Host detects the error and the host it was attempting;  Route Error is sent back to the sender the packet – original src

A B C E D G H F G RERR Route Cache (A) G: A, B, D, G G: A, C, E, H, G F: B, C, F Route Maintenance

Interference-based routing

Examples for interference based routing

Reactive: Ad-Hoc On-demand Distance Vector Routing (AODV)  By Perkins and Royer  Sender tries to find destination:  broadcasts a Route Request Packet (RREQ).  Nodes maintain route cache and use destination sequence number for each route entry  State is installed at nodes per destination  Does nothing when connection between end points is still valid  When route fails  Local recovery  Sender repeats a Route Discovery

Route Discovery in AODV 1 Propagation of Route Request (RREQ) packet

Route Discovery in AODV 2 Path taken by Route Reply (RREP) packet

In case of broken links…  Node monitors the link status of next hop in active routes  Route Error packets (RERR) is used to notify other nodes if link is broken  Nodes remove corresponding route entry after hearing RERR