IP: Global Internet. Teknologi Jaringan Komputer. Johny Moningka Fakultas Ilmu Komputer Universitas Indonesia

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1 IP: Global Internet Teknologi Jaringan Komputer Johny Moningka Fakultas Ilmu Komputer Universitas Indonesia Semester 2003/2004 Versi: 1.01 Agenda Global Internet (Bab 4.3) Subnetting => Bab Classless Routing (CIDR) => Bab Versi: 1.1 1

2 Evolutions Struktur Internet 1990-an. Tree, centered pada suatu backbone. National Science Foundation (US) funded. Stanford NSFNET backbone ISU Berkeley BARRNET PARC NCAR Westnet UNM UNL MidNet KU UA 3 Versi: 1.1 Evolutions (continued) Internet (saat ini): multipel backbone => network providers. Sulit untuk dibuat strukturisasi => kumpulan network dari berbagai hirarkis Stanford Service Providers ISU Berkeley BARRNET PARC NCAR Westnet UNM UNL MidNet KU UA 4 Versi: 1.1 2

3 Virtual Geographies Dikenal dua cara utk identifikasi host di Internet: Internet domain names (digunakan oleh orang, publikasi dsb, string karakter, mudah di-ingat, dengan, sub-subdomain, subdomain, domain dst. mis.: telaga.cs.ui.ac.id). IP address: network number sbg domain (diproses dan dimengerti oleh router). Hirarkis: cara terbaik untuk strukturisasi forwarding paket IP di Internet Bagaimana hirarki didefinisikan untuk dapat dimengerti oleh router dan skalabilitas besar? 5 Versi: 1.1 Review: IP Class Address IP Addresses occupy the following valid ranges according to Class class A 0 network host B 10 network host C 110 network host D 1110 multicast address 32 bits Versi: 1.1 3

4 Problem: Scope of IP Address Space Contoh: Suatu organisasi memerlukan 1000 alamat IP. Satu kelas C tidak cukup (hanya 254 hosts). Jika menggunakan kelas B terlalu besar (64 K hosts), banyak IP address tidak digunakan. (Note: hanya kelas B yang ada!) Masalah: Tidak efisien alokasi pemakaian alamat IP. Terlalu banyak network untuk routing table (setiap network mempunyai 1 entry) Q: Bagaimana mengalokasikan alamat IP utk perusahaan dengan 1000 komputer? Q: Bagaimana dengan perusahaan yg menggunakan 10 komputer dan merencanakan kelak akan menggunakan 1000 komputer? 7 Versi: 1.1 IP Address Evolutions: Subnetting Menambahkan level address/routing hierarcy: subnet Subnet masks: menentukan bagian mana yang menjadi network id (numbers) Subnets visible to routers only within site Original 1 0 Net ID Host ID Address Subnetted 1 0 Net ID Subnet ID Host ID Address Network number Class B address Host number Subnet mask ( ) Network number Subnet ID Host ID Subnetted address 8 Versi: 1.1 4

5 Network Mask: subnetting Class B IP Address Class B Subnet Mask Network Address IP Address Subnet Mask Subnet Address Broadcast Address Menggunakan 3 bits subnet mask, jumlah subnetworks yang dibangun adalah: 2^n 2 => 2^3 2 = 6 subnetworks. 9 Versi: 1.1 Subnet Mask Class A: Class B: Class C: s 16 1 s 24 1 s Class A subnet mask: Class B subnet mask: Class C subnet mask: Versi: 1.1 5

6 Subnet Example (1) What is the subnetwork address if the destination address is and the subnet mask is ? Apply the AND operation subnetwork address Note: 240 = Versi: 1.1 Subnet Example (2) H1 R1 Subnet mask: Subnet number: H3 Subnet mask: Subnet number: R Subnet mask: Subnet number: H Forwarding table at router R1 Subnet Number Subnet Mask Next Hop interface interface R2 12 Versi: 1.1 6

7 Supernetting Class A and B addresses are almost depleted. Class C is available, but most organization needs more than 256 hosts in the network. Solution: use supernetting. Combine several class C networks to create a supernetwork (less number of 1 s than default mask) A supernet mask is reverse of a subnet mask Subnet Mask Default Mask Supernet Mask 13 Versi: 1.1 IP Address Evolution Continued Subnets memberikan kemudahan routing dan penggunaan alokasi IP address dalam organisasi (intra domain). TIDAK mengurangi masalah alokasi IP address global => tekanan terhadap persediaan kelas B. 14 Versi: 1.1 7

8 IP Addressing: CIDR Solusi: CIDR => Classless Inter-Domain Routing Eliminasi class dalam IP address => hanya mengenal subnet address format: a.b.c.d/x, where x is # bits in network portion of address, atau x => subnet masks. network part Notation: / 23 host part 15 Versi: 1.1 IP addresses: Get from ISP s Network (network portion): get allocated portion of ISP s address space: ISP's block /20 Organization /23 Organization /23 Organization / Organization /23 16 Versi: 1.1 8

9 CIDR: Classless Inter-Domain Routing Address format: <IP address/prefix P> The prefix denotes the upper P bits of the IP address. Idea - use aggregation - provide routing for a large number of customers by advertising one common prefix. This is possible because nature of addressing is hierarchical Summarization reduces the size of routing tables, but maintains connectivity. Aggregation scalability and survivability of the Internet 17 Versi: 1.1 Problem : Routing Table Size Without CIDR: service provid er Global Internet All routers must learn all internal routes With CIDR: service provid er /16 Global Internet All routers need only learn summary address 18 Versi: 1.1 9

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