1. 1 Pertemuan 21 Internetworking Matakuliah: H0174/Jaringan Komputer Tahun: 2006 Versi: 1/0

2. 2 Learning Outcomes Pada akhir pertemuan ini, diharapkan mahasiswa akan mampu : Menunjukkan internetworking

3. 3 Outline Materi Bridge Router Switch

4. 4 Internetworking Terms End System (ES) –Device attached to one of the networks of an internet –Supports end-user applications or services Intermediate System (IS) –Device used to connect two networks –Permits communication between end systems attached to different networks

5. 5 How Networks Differ 5-43

6. 6 Internetworking Devices Types of devices for interconnecting LAN  Bridge  Routers  Layer 2 switch  Layer 3 switch

7. 7 Interconnecting Networks (a) Two Ethernets connected by a switch. (b) Two Ethernets connected by routers.

8. 8 Internetworking Components Bridge –IS (Intermediate System) used to connect two LANs using similar LAN protocols to expand beyond single LAN –Address filtering- passing on packets to the required network only –OSI layer 2 (Data Link) –Bridge is simple, minimal processing Router –Connects two (possibly dissimilar) networks –Uses internet protocol present in each router and end system –OSI Layer 3 (Network)

9. 9 Connection of Two LANs

10. 10 Functions of a Bridge Read all frames transmitted on one LAN and accept those address to any station on the other LAN Using MAC protocol for second LAN, retransmit each frame No modification to content or format of frame, no encapsulation (Exact bitwise copy of frame) May be more than one bridge to cross May connect more than two LANs Bridging is transparent to stations

11. 11 Bridge Protocol Architecture MAC level –Station address is at this level Bridge does not need LLC layer –It is relaying MAC frames Can pass frame over external communication system WAN link –Capture frame –Encapsulate it –Forward it across link –Remove encapsulation and forward over LAN link

12. 12 Address Learning Preload forwarding address database Learn forwarding address –When frame arrives at port X, it has come from the LAN attached to port X –Use the source address to update forwarding database for port X to include that address –Timer on each entry in database –Each time frame arrives, source address checked against forwarding database

13. 13 Spanning Tree Algorithm Address learning works for tree layout –i.e. no closed loops For any connected graph there is a spanning tree that maintains connectivity but contains no closed loops Each bridge assigned unique identifier Exchange between bridges to establish spanning tree

14. 14 Router Complex large LANs need alternative routes –Load balancing –Fault tolerance Routing selected for each source-destination pair Routers do all IP-level processing in software High-speed LANs and high-performance layer 2 switches pump millions of packets per second Layer 3 switches –Implementpacket-forwarding logic of router in hardware Two categories: Packet by packet and Flow base

15. 15 Problems with Routers Routers do all IP-level processing in software –High-speed LANs and high-performance layer 2 switches pump millions of packets per second –Software-based router only able to handle well under a million packets per second Solution: layer 3 switches –Implement packet-forwarding logic of router in hardware Two categories –Packet by packet –Flow based

16. 16 Layer 3 Switch Packet by Packet –Operates insame way as traditional router –Order of magnitude increase in performance Flow-based switch –Tries to enhance performance by identifying flows of IP packets of same source and destination –Done by observing ongoing traffic –Once flow is identified, predefined route can be established