Transcript Basic TCP/IP Networking

Basic TCP/IP Networking
WeeSan Lee <[email protected]>
http://www.cs.ucr.edu/~weesan/cs183/
Roadmap
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The Internet
How the Internet is managed?
TCP/IP
IP Addresses
CIDR
IPv6
IP Address Allocation
NAT
Hostname and IP Address Assignment
Routing vs Forwarding
The Internet
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Inter-networks via TCP/IP
Originated from ARPANET
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ARPANET → NSFnet
NSFnet was commercialized in 1994
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Established in 1969 by DARPA
Not invented by Al Gore!!!
With help from Routing Arbiter Project
Now, the Internet is a collection of networks
managed by ISPs, who exchange traffic at NAPs
How the Internet is managed?
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ISPs manage their own networks
Several organizations involve
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ICANN
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IETF
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The Internet Corporation for Assigned Names and
Numbers
The Engineering Task Force
RFC-Editor
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Request For Comments
RFC2555, 30 Years of RFCs
TCP/IP
HTTP
FTP
SSH
SMTP
TCP
ICMP
ARP/RARP
DNS
UDP
IP
IGMP
Hardware Interface
Application layer
Transport layer
Network layer
Link layer
TCP/IP (cont)
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"Be liberal in what you accept, and
conservative in what you send." – Jon Postel
(1943-1998)
TCP/IP (cont)
HTTP
HTTP
TCP
TCP
IP
IP
Ethernet
The
Internet
Ethernet
IP Addresses
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IPv4
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4 bytes, eg. 138.23.169.9
Network & Host portion
Historical Internet address classes
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A
B
C
D
E
1-126
N.H.H.H
128-191 N.N.H.H
192-223 N.N.N.H
224-239
240-255
IP Addresses (cont)
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Problems
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Class B addresses were running out by 1995
Routing tables were too big to fit into memory
Fragmentation
Solutions
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Short-term
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CIDR – Classless Inter-Domain Routing
Long-term
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IPv6
CIDR
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No more classes
Uses prefix, /00 notation, eg.
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138.23.0.0/16
Can be difficult to compute, eg. /26
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Uses http://www.jodies.de/ipcalc
IPv6
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16 bytes
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128 bits
Consume more memory on routers?
Ready for years but too costly to deploy
IP Address Allocation
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ICANN delegates blocks of addresses to 5
regional Internet registries
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ARIN
APNIC
RIPE
AfriNIC
LACNIC
NAT
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Network Address Translation
Translation private IP addresses into public
Private IP addresses (RFC1918)
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A 10.0.0.1/8
B 172.16.0.0/12
C 192.168.0.0/16
It’s a hack but it works
Some researchers hate it since it breaks e2e
Hostname and IP Address Assignment
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/etc/hosts
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DNS
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127.0.0.1
localhost
138.23.169.9 eon.cs.ucr.edu eon
Domain Name System
DHCP
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Dynamic Host Configuration Protocol
Hostname and IP Address Assignment
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/bin/hostname
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Set or display current hostname
/bin/ifconfig
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Enable and disable a network interface
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$ ifconfig eth0 up
$ ifconfig eth0 down
Set IP address, subnet mask, broadcast address
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$ ifconfig eth0 138.23.169.9 netmask 255.255.255.128
$ ifconfig eth0
$ ifconfig -a
Routing vs Forwarding
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Routing
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Forwarding
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A process to build up a routing table
A process to forward packets from one NIC to another by
consulting the routing table
Routing table
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$ netstat -rn
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Kernel IP routing table
Destination Gateway
192.168.0.0 0.0.0.0
169.254.0.0 0.0.0.0
0.0.0.0
192.168.0.1
Genmask
255.255.255.0
255.255.0.0
0.0.0.0
Flags
U
U
UG
MSS
0
0
0
Window irtt Iface
0
0 eth0
0
0 eth0
0
0 eth0
Reference
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LAH
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Ch 12: TCP/IP Networking