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OSI network layer

OSI network layer. Application. HTTP, FTP, TFTP, SMTP etc. Data stream. Presentation. Application. Session. Transport. Transport. TCP, UDP. Segment. Network. Internet. IP. Packet. Data link. Ethernet, WAN technologies. Frame. Network Access. Physical. Bits. OSI network layer.

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OSI network layer

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  1. OSI network layer Jaringan Komputer_D3 TT

  2. Application HTTP, FTP, TFTP, SMTP etc Data stream Presentation Application Session Transport Transport TCP, UDP Segment Network Internet IP Packet Data link Ethernet, WAN technologies Frame Network Access Physical Bits OSI network layer • OSI model layer 3 • TCP/IP model Internet layer Jaringan Komputer_D3 TT

  3. Network layer topics • IP version 4 – the most common layer 3 routed protocol • Dividing hosts into groups – why and how • Routing – sending packets the right way • Routing – how routers learn routes • IP addressing – in chapter 6 Jaringan Komputer_D3 TT

  4. Purpose of layer 3 • Decide how to get the data from source to destination, then route it. Jaringan Komputer_D3 TT

  5. Layer 3 protocol A layer 3 protocol such as IP version 4 must: • Provide an addressing scheme to identify networks and individual hosts • Encapsulate a segment from layer 4 into a packet and include addresses • Direct the packet across one or many networks to the destination host • Decapsulate (remove the packet header) and give the segment to layer 4. Jaringan Komputer_D3 TT

  6. Network layer protocols • Internet Protocol version 4 (IPv4) – the most common • Internet Protocol version 6 (IPv6) – designed to replace version 4 eventually • Novell Internetwork Packet Exchange (IPX) • AppleTalk • Connectionless Network Service (CLNS/DECNet) Jaringan Komputer_D3 TT

  7. Novell Internetwork Packet Exchange (IPX) • IPX (bahasa Inggris: Internetwork Packet Exchange) adalah protokol jaringankomputer yang digunakan oleh sistem operasiNovell NetWare pada akhir dekade 1980an hingga pertengahan dekade 1990an. IPX adalah protokol komunikasi tanpa koneksi (connectionless), seperti halnya Internet Protocol dan User Datagram Protocol pada kumpulan protokolTCP/IP. Selain membutuhkan protokol IPX, Novell Netware juga membutuhkan protokol tingkat tinggi bernama Sequenced Packet Exchange (SPX) dan Network Control Protocol (NCP). Protokol ini diturunkan oleh Novell dari protokol IDP yang terdapat di dalam Xerox Network Services. • IPX digunakan untuk melakukan pemetaan paket-paket data dari satu titik di dalam jaringan ke titik lainnya melalui sebuah internetwork. IPX beroperasi di lapisan jaringan (lapisan ketiga pada model OSI), dan dapat digunakan di dalam teknologi Ethernet, Token Ring, dan protokol lapisan data-link lainnya. IPX memang dahulu pernah digunakan pada Local Area Network (LAN) berbasis Novell NetWare sebelum akhirnya Novell menggantinya dengan TCP/IP saat merilis NetWare 5.x. Sebelum diganti dengan TCP/IP, protokol ini merupakan protokol yang sangat populer. Jaringan Komputer_D3 TT

  8. AppleTalk • AppleTalk adalah sebuah protokol jaringan yang dikembangkan khusus untuk jaringan yang terdiri atas komputer-komputer Apple Macintosh, yang mengizinkan para penggunanya untuk saling berbagi berkas dan printer agar dapat diakses oleh pengguna lainnya. • AppleTalk merupakan teknologi yang sudah dianggap usang yang kini telah digantikan oleh Apple Open Transport, yang juga mendukung AppleTalk itu sendiri, protokol TCP/IP dan beberapa protokol jaringan lainnya. Jaringan Komputer_D3 TT

  9. Arsitektur AppleTalk dan perbandingannya dengan model referensi OSI Jaringan Komputer_D3 TT

  10. IP characteristics • Designed with low overhead for speed – it does only what it needs to do. • Connectionless – does not set up connection with destination before sending packet. • Best effort (unreliable) no guarantee of safe delivery, no checking or resending. • Independent of media, but does need to know maximum packet size. Jaringan Komputer_D3 TT

  11. Network layer encapsulation Segment from transport layer Packet header added to make IP packet Sent to data link layer for further encapsulation into frame Jaringan Komputer_D3 TT

  12. IP address of source host, needed so reply can be sent. IP address of destination host, needed so routers can find route. IPv4 packet header fields Jaringan Komputer_D3 TT

  13. Reduced by 1 at each router. Packet dropped if it goes to 0. TCP or UDP used in Transport layer. IPv4 packet header fields Jaringan Komputer_D3 TT

  14. Priority for QoS. E.g. voice data has higher priority than e-mail. For checking if header has been corrupted. IPv4 packet header fields Jaringan Komputer_D3 TT

  15. If router has to split a packet, this gives order for putting pieces together. Shows if packet has been fragmented or must not be fragmented. IPv4 packet header fields Jaringan Komputer_D3 TT

  16. Version 4. Header length. Length of whole packet. IPv4 packet header fields Jaringan Komputer_D3 TT

  17. Splitting up networks Fully switched network, each device has its own bandwidth. You could have hundreds of computers. Why split it up? Too large to manage efficiently Too much broadcast traffic - congestion Too many addresses for switches to remember Lack of security Jaringan Komputer_D3 TT

  18. How to split the network • Geographically – different sites • Purpose – what software and shared resources do people use? How much bandwidth do they use? • Ownership – different companies or departments in a company, security requirements Jaringan Komputer_D3 TT

  19. Use a router • Limits broadcasts • Can provide security • Addressing scheme based on networks - hierarchical Jaringan Komputer_D3 TT

  20. IPv4 hierarchical address • 32 bits in four 8-bit octets, written in decimal • Network part then host part • Here network part (prefix) is 24 bits /24 • Length of network part can vary. Jaringan Komputer_D3 TT

  21. Message to same network Jaringan Komputer_D3 TT

  22. Message to different network Jaringan Komputer_D3 TT

  23. Default gateway • Each PC is configured with an IP address and a default gateway. • The default gateway is the IP address of a router port on the same network as the PC. • It is the router’s job to handle messages to other networks. • Each router port is on a different network and has a different IP address. Jaringan Komputer_D3 TT

  24. Hops • A packet may pass through many routers on its journey. • The trip from one router to the next is called a hop and the next router is called the next hop router. • Each router looks at the IP address in the packet header and decides what to do with the packet next. Jaringan Komputer_D3 TT

  25. Routing table and forwarding • Each router has a routing table. This contains a list of known networks and the best way to get there – outgoing port and address of next-hop router. • The router looks at the IP address of a packet. It decides which network this address is on.If it knows the network it forwards the packet.If it does not know the network it drops the packet. Jaringan Komputer_D3 TT

  26. Directly connected The networks of the router’s own interfaces go into the routing table. Jaringan Komputer_D3 TT

  27. Other networks • Routes to other networks can be configured by an administrator (static routes) • Or they can be learned from another router using a routing protocol (dynamic routes) • A router can have a default route. Packets for unknown networks go on this route instead of being dropped. Jaringan Komputer_D3 TT

  28. Routing protocols • Routers learn routes from each other and put them in their routing tables. • A routing protocol is the set of rules they use to swap information. • These routes are dynamic routes Jaringan Komputer_D3 TT

  29. Static Dynamic routes routes • Entered by administrator • Time consuming, different for each router • Must be updated if routes change • Little processing • No bandwidth used • Gives nothing away • Learned from other routers • Start the protocol then it runs by itself • Automatically updates when routes change • More processing • Uses bandwidth • Gives away information Jaringan Komputer_D3 TT

  30. Thank You Ref: S Ward Abingdon and Witney College Jaringan Komputer_D3 TT

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