Transcript Basic IP Protocol

Basic IP Protocol
Natawut Nupairoj, Ph.D.
Department of Computer Engineering
Chulalongkorn University
Outline
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Overview.
IP Address.
Subnetting.
IP Routing.
ICMP.
An Internet According to TCP/IP
TCP vs. OSI Model
Network Layer
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IP:Internet Protocol
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ICMP: Internet Control Message Protocol
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Unreliable (best-effort)
Connectionless
IP datagram
Request/response/error messages
Ping, traceroute
Encapsulated in IP datagrams.
IGMP: Internet Group Management Protocol
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Join/leave IP multicast groups.
Encapsulated in IP datagrams.
Transport Layer
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TCP
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UDP (datagram)
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Reliable (timeout/retransmission mechanism)
Connection-oriented.
TCP segment
Telnet, rlogin, SMTP, HTTP, FTP
Unreliable but low-overhead
DNS, TFTP, BOOTP, SNMP
Connecting thru “port” (SAP).
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16-bit numbers
well-known port number: HTTP(80), FTP(20), etc.
Port
IP Datagram
IP Address
IP Address Classes
Decimal Notation
IP Class Ranges
Network and Host Address
Example
Example: Subnet
Subnetting
Netmask
Basic IP Routing
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Hop-by-hop using routing table.
Routing table entry:
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Destination IP address:
host address - non-zero host ID
 network address - host ID = 0
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Gateway IP address:
next-hop router.
 directly connected.
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Basic IP Routing
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Flags
destination IP: host or network address
 gateway IP: router or direct connect
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Network interface should be used for
transmission.
IP Routing Mechanism
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Search routing table for an entry:
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Matches the complete IP address (both network and host
IDs).
Matches the destination network ID.
Default route.
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If found, send to the gateway IP address (either
next-hop or directly connected interface).
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Otherwise, the datagram is undeliverable (router
issues an ICMP error message).
Internet Control Protocols
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To provide support for IP.
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ARP
RARP
ICMP
All data for these protocols are encapsulated
in IP datagrams.
ICP: ARP
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ARP: Address Resolution Protocol
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To send a packet to the destination, a host must
know the destination physical network address.
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The sender/router must convert from IP address to
physical network address (ie. Ethernet address).
When a host wants to find a physical address:
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It broadcasts an ARP request containning an IP address.
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The owner (or designated responder) replies with its own
network address.
ARP response can be cached.
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Address Resolution Protocol
ICP: RARP
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Reverse Address Resolution Protocol.
The reverse of ARP.
For diskless workstation.
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X Terminal
Other related protocols:
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bootp
tftp
ICP: ICMP
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Internet Control Message Protocol
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Communicate error messages and other conditions
for IP and higher layers.
Message Types:
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Status checking: ping.
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Error messages: destination unreachable, network
unreachable, etc.
Flow control: source quench.
Routing control: redirect, etc.
Information retrieval: timestamp request, etc.
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Important ICMP Messages
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Echo:
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Destination, network, port unreachable messages:
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Used by the traceroute program.
Time Exceeded:
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for ping program.
TTL = 0 during transit or reassembly.
Also used by the traceroute program.
Source quench:
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flow control.
the receiver informs the sender that it is running out of
buffer and starts dropping datagrams.