Agenda. Problem: There is more than one network! Internetworking: IP Companion Protocol. Case: IP & Ethernet. IPv4 Address Translation support

Agenda Problem: There is more than one network!

Internetworking: IP – Companion Protocol

Internetworking (Bab 4.1) • • • • • • •

Teknologi Jaringan Komputer Johny Moningka ([email protected])

Basis internetwork Service model & Format Packet Global Address Address Translation: ARP (Bab 4.1.5) Host Configuration: DHCP (Bab 4.1.6) Error Reporting: ICMP (Bab 4.1.7) Virtual Private Networks (Bab 4.1.8)

Fakultas Ilmu Komputer Universitas Indonesia Semester 2003/2004 Versi: 1.01

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IPv4 Address Translation support

Case: IP & Ethernet

Identifikasi alamat IP host ke LAN physical addresses (i.e alamat Ethernet) Masalah:

App

Hdr

Ethernet: H1 -> R1

H7

H3

IP Datagram Hdr

Paket data yang dikirimkan dalam internetworking Versi: 1.1

IP address diberikan sesuai dengan physical address (encode) Jarang digunakan: sulit untuk penyesuaian dan mapping.

R3

H8 Hdr

Fixed table

Ethernet: R3 -> H8

Terdapat tabel translasi yang disimpan pada suatu “central repository” Tabel didistribusikan melalui central tsb

R1 R4 (point-to-point)

Automatically generated table

R2

Data

5

Data

Hdr

Hard-coded

Network 1 (Ethernet)

Network 2 (Ethernet) Data

Ethernet

Data

4

IP: H1-> H8

Hdr

Data

H2

IP

TCP Segment

Hdr

IP to Physical Address Translation Data

H1

Network

Data

Ethernet Frame

Forwarding IP Packet

IP: H1 -> H8

TCP / UDP

Paket data yang disampaikan dari satu node ke node yang lain (direct, pulsa signal/fisik) Versi: 1.1

Hdr

Transport

Link

Mekanisme: korelasi antara IP address suatu host dengan alamat fisik/hardware network adapter 3

Paket data yang dibuat oleh end-system (host)

Layer

Rute IP dapat melalui berbagai transit jaringan fisik yang berbeda (address berbeda). Data (paket IP) harus disampaikan ke jaringan fisik dimana host tujuan berada Host (tujuan) hanya dapat menerima (mendengar) paket melalui physical address (network adapter/interface)

Data

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Hdr

Terdapat protokol khusus (mis. ARP) untuk membangun tabel pada setiap host Update & clean-up: timeout untuk entry tabel.

IP: H1-> H8 (R2 => R4) Versi: 1.1

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Address Resolution Protocol (ARP)

Example

ARP (RFC 826):

H1 akan mengirim paket ke IP address: 150.100.76.22, tapi tidak ada informasi physical address pada tabel ARP.

Sistim menyimpan tabel mapping alamat-alamat IP dan alamat physical Jika (alamat IP tidak berada dalam tabel) Broadcast ARP Request (kemampuan broadcast) Target respond (IP address) => alamat physical Protokol ARP bertugas: inquiry (broadcast) untuk mendapatkan data pasangan alamat IP dan physical address.

H1

H2

H3

H4

150.100.76.20 150.100.76.21 150.100.76.22 150.100.76.23

Setiap node akan meproses broadcast paket ARP dan membandingkan IP (target) dengan IP sendiri

H1: ARP request “what is the MAC address of 150.100.76.22”? H1

H2

H3

Jika sama => ARP response ke node originator request ARP

H4 Figure 8.8

H3: ARP response “My MAC address is 08-00-5A-C5-3B-94” 7

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Example: ARP & Default Router

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ARP Packet Format 0

Source host A first decides whether dest. Host is on the same network

8

16

Hardware type = 1 HLen = 48

PLen = 32

31 ProtocolT ype = 0x0800 Operation

SourceHardwareAddr (bytes 0 – 3)

by comparing the network ids of the 2 addresses

SourceHardwareAddr (bytes 4 – 5) SourceProtocolAddr (bytes 0 – 1)

if yes, find destination’s physical address via ARP, send data if not: ?

SourceProtocolAddr (bytes 2 – 3) TargetHardwareAddr (bytes 0 – 1) TargetHardwareAddr (bytes 2 – 5) TargetProtocolAddr (bytes 0 – 3)

ARP Request Format • HardwareType: type of physical network (e.g., Ethernet) • ProtocolType: type of higher layer protocol (e.g., IP) • HLEN & PLEN: length of physical and protocol addresses • Operation: request or response • Source/Target-Physical/Protocol addresses 9

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Agenda

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Host Configuration Bagaimana host mendapatkan IP address:

Problem: There is more than one network!

Statik: setup (hard coded) oleh network admin.


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Menambahkan suatu host baru ke dalam jaringan IP


Informasi apa saja yang diperlukan? (statis) Remember: host sering berpindah, konfigurasi (router) berubah dst => IP address tergantung koneksi dengan jaringan (logical) Tidak dapat disetup oleh “manufacturer” komputer/OS: IP address independent dari komputer. Versi: 1.1

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DHCP Server

Dynamic Host Configuration Protocol (DHCP)

Cara dinamik alokasi IP address untuk otomatisasi pemberian IP address komputer

How does a host find the address of a DHCP server? Host sends a DHCP DISCOVER “limited IP broadcast packet”, with destination address 255.255.255.255 Routers never forward such a packet, so it stays within LAN

Pengelola jaringan (administrator): centralized control untuk distribusi IP address (policy dan setup) Efektif: jaringan yang besar dan dinamis (mis. mobile computer). Perlu server yang menjadi rujukan (DHCP server).

IP Router 255.255.255.255

LAN1

LAN2 DHCP Server

Requesting Host 13

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DHCP: Server Response

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DHCP: request reply DHCP: Dynamic Host Configuration

DHCP server selects a dynamic IP addr. from pool

Protocol: dynamically get address from DHCP server: “plug-and-play”

Maps host’s MAC address to the dynamic IP address Hosts cannot keep dynamic IP addresses indefinitely Timeout/lease by DHCP

host requiring IP addr broadcasts “DHCP discover” msg DHCP server responds with “DHCP offer” msg host requests IP address: “DHCP request” msg DHCP server sends address: “DHCP ack” msg

• 3 days for Windows NT, 8 days for Windows 2000, • Configurable when starting DHCP server

Host must periodically renew lease, otherwise IP address goes back into pool of available addresses

DHCP is implemented as an application-level protocol on top of UDP and IP 15

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Agenda

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Internet Control Message Protocol ICMP is an integral part of the TCP/IP specification (defined in RFC-792)

Problem: There is more than one network! Internetworking (Bab 4.1) • • • • • • •

Versi: 1.1

ftp://ftp.isi.edu/in-notes/rfc792.txt


Why need ICMP? “best effort” does not mean careless IP does not have a means itself to provide feedback information about problems in packet delivery

ICMP is not make IP delivery reliable 17

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report information or errors only, does not prescribe cures

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ICMP Message Format (1)

ICMP Message Format (2)

ICMP messages berada di dalam (encapsulated) sebagai data IP datagrams IP-level routing used to move ICMP messages through a network IP uses protocol type = 1 to indicate ICMP payload

TYPE: Type of ICMP message CODE: Used by some types to indicate a specific condition CHECKSUM: Checksum over full message Contents depend on TYPE and CODE 19

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Example ICMP Message Types

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Agenda

Queries

Problem: There is more than one network!

TYPE = 8: Echo request TYPE = 0: Echo reply TYPE = 13: Time stamp request TYPE = 14: Time stamp reply


Errors TYPE = 3: Destination unreachable • • • •

Versi: 1.1

CODE = 0: Network unreachable CODE = 1: Host unreachable CODE = 2: Protocol unreachable CODE = 3: Port unreachable


TYPE = 11: Time exceeded • CODE = 0: Time-to-live equals 0 in transit 21

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Virtual Private Networks

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Virtual Networks

Goal: mengendalikan koneksi

Contoh:

Konektivitas IP => jaringan publik Bagaimana melindungi/membatasi koneksi ke jaringan yang digunakan bersama?

Prasyarat: memanfaatkan jaringan komputer Internet utk menghubungkan berbagai kantor cabang + kantor pusat => suatu jaringan private (mis. koneksi dan data dilindungi). Solusi: melindung paket IP (asli) => enkapsulasi pada saat di forward dlm jaringan Internet

Virtual Private Network Mekanisme membangun koneksi dengan fitur tambahan (virtual) diatas koneksi IP datagram. Koneksi IP: sebagai jembatan (shared networks) Virtual networks: services baru dengan fitur baru untuk mengontrol koneksi, mislkan keamanan (data disandikan enkripsi) 23

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Versi: 1.1

• Membuat “tunnel” (dedicated channel): virtual end-point pada pasangan-pasangan node (routers) dari jaringan lokal di kantor. • IP address dari end-point router menjadi bagian virtual connections tsb => enkapsulai paket IP ke dalam paket IP dgn target address end-point tsb. 24

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Tunneling

Example: Tunneling

IP Tunnel

R1: 2 physical interface (0: internal, 1: external); 1 virtual (tunnel). R1 proses paket IP tujuan network 2 => enkapsulasi paket IP, dengan alamat R2 (10.0.0.1); => paket IP baru dgn tujuan R2 Forward melalui jaringan internet ke R2 R2 proses paket => strip header IP => IP paket dgn tujuan host di network 2.

Tunnel: membungkus paket ke dalam paket Virtual point-to-point link antar dua pasang node IP (mis. R1 dan R2 => setup virtual tunnel)

Network Network 11

R1

Internetwork Internetwork

Network Network 22

R2

IP Tunnel 10.0.0.1 IP Dest = 2.x IP Payload

IP Dest = 10.0.0.1 IP Dest = 2.x IP Payload

IP Dest = 2.x IP Payload

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Network Number

Next Hop

1

Interface 0

2

Virtual Interface 0

Default

Interface 1

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Tunneling Keuntungan Transparent transmission of packets over a heterogeneous network Only need to change relevant routers

Kerugian Increases packet size Processing time needed to encapsulate and unencapsulate packets Management at tunnel-aware routers

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Agenda. Problem: There is more than one network! Internetworking: IP Companion Protocol. Case: IP & Ethernet. IPv4 Address Translation support

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