IP: Global Internet
Teknologi Jaringan Komputer Johny Moningka (
[email protected]) Fakultas Ilmu Komputer Universitas Indonesia Semester 2003/2004 Versi: 1.01
Agenda Global Internet (Bab 4.3) Subnetting => Bab 4.3.1 Classless Routing (CIDR) => Bab 4.3.2
2
Versi: 1.1
1
Evolutions Struktur Internet 1990-an. Tree, centered pada suatu backbone. National Science Foundation (US) funded.
NSFNET backbone
Stanford
ISU
BARRNET regional Berkeley
PARC
UNL
UNM
NCAR
MidNet regional
…
Westnet regional
KU
UA 3
Versi: 1.1
Evolutions (continued) Internet (saat ini): multipel backbone => network providers. Sulit untuk dibuat strukturisasi => kumpulan network dari berbagai hirarkis Service Providers
Stanford BARRNET regional Berkeley
PARC
UNM
NCAR
MidNet regional
…
Westnet regional
ISU
UNL
KU
UA 4
Versi: 1.1
2
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
B
10
C
110
D
1110
host
network
host
network multicast address
32 bits
6
host
1.0.0.0 – 127.255.255.255 128.0.0.0 – 191.255.255.255 192.0.0.0 – 223.255.255.255 224.0.0.0 – 239.255.255.255
Versi: 1.1
3
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 16.000 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 Address Subnetted 1 0 Address
Net ID
Host ID Subnet ID
Net ID Network number
Host ID
Host number
Class B address 111111111111111111111111
00000000
Subnet mask (255.255.255.0) Network number 8
Subnet ID
Subnetted address
Host ID Versi: 1.1
4
Network Mask: subnetting 10001100.10110011.11110000.11001000 11111111.11111111.00000000.00000000 --------------------------------------------------------
140.179.240.200 255.255.000.000
Class B IP Address Class B Subnet Mask
10001100.10110011.00000000.00000000
140.179.000.000 Network Address
10001100.10110011.11011100.11001000 11111111.11111111.11100000.00000000 -------------------------------------------------------10001100.10110011.11000000.00000000 10001100.10110011.11011111.11111111
140.179.220.200 255.255.224.000
IP Address Subnet Mask
140.179.192.000 140.179.223.255
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:
11111111 00000000 00000000 00000000
8 1’s
Class B:
11111111 11111111 00000000 00000000
16 1’s
Class C:
11111111 11111111 11111111 00000000
24 1’s
• Class A subnet mask: 255.0.0.0 • Class B subnet mask: 255.255.0.0 • Class C subnet mask: 255.255.255.0
10
Versi: 1.1
5
Subnet Example (1) What is the subnetwork address if the destination address is 128.2.4.12 and the subnet mask is 255.255.240.0? Apply the AND operation 10000000 00000010 00000100 00001100 11111111 11111111 11110000 00000000 --------------------------------------------------------------10000000 00000010 00000000 00000000 Î 128.2.0.0 subnetwork address Note: 240 = 128+64+32+16 11
Versi: 1.1
Subnet Example (2) Subnet mask: 255.255.255.128 Subnet number: 128.96.34.0 128.96.34.15
128.96.34.1
H1 R1
Subnet mask: 255.255.255.128 Subnet number: 128.96.34.128
128.96.34.130
128.96.34.139
128.96.34.129
H2 R2
H3 128.96.33.14
128.96.33.1
Subnet mask: 255.255.255.0 Subnet number: 128.96.33.0
12
Forwarding table at router R1 Subnet Number Subnet Mask 128.96.34.0 255.255.255.128 128.96.34.128 255.255.255.128 128.96.33.0 255.255.255.0
Next Hop interface 0 interface 1 R2
Versi: 1.1
6
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. 11111111 11111111 11111111 111 00000
Subnet Mask
11111111 11111111 11111111 000 00000
Default Mask
11111111 11111111 11111000 000 00000
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
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
host part
11001000 00010111 00010000 00000000 Notation: 200.23.16.0 / 23 15
Versi: 1.1
IP addresses: Get from ISP’s Network (network portion): get allocated portion of ISP’s address space: ISP's block
11001000 00010111 00010000 00000000
200.23.16.0/20
Organization 0
11001000 00010111 00010000 00000000
200.23.16.0/23
Organization 1
11001000 00010111 00010010 00000000
200.23.18.0/23
Organization 2 ...
11001000 00010111 00010100 00000000 ….. ….
200.23.20.0/23 ….
Organization 7
11001000 00010111 00011110 00000000
200.23.30.0/23
16
Versi: 1.1
8
CIDR: Classless Inter-Domain Routing Address format:
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: 232.71.0.0 232.71.1.0 232.71.2.0 ….. 232.71.255.0
service provid er
232.71.0.0 232.71.1.0 232.71.2.0 ….. 232.71.255.0
Global Internet All routers must learn all internal routes
With CIDR: 232.71.0.0 232.71.1.0 232.71.2.0 ….. 232.71.255.0
18
service provid er
Global Internet 232.71.0.0/16 All routers need only learn “summary” address
Versi: 1.1
9
