Basic TCP/IP Networking

1
Basic TCP/IP Networking

• WeeSan Lee ltweesan_at_cs.ucr.edugt
• http//www.cs.ucr.edu/weesan/cs183/

2
Roadmap

• 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

3
The Internet

• Inter-networks via TCP/IP
• Originated from ARPANET
• Established in 1969 by DARPA
• Not invented by Al Gore!!!
• ARPANET ? NSFnet
• NSFnet was commercialized in 1994
• With help from Routing Arbiter Project
• Now, the Internet is a collection of networks
  managed by ISPs, who exchange traffic at NAPs

4
How the Internet is managed?

• ISPs manage their own networks
• Several organizations involve
• ICANN
• The Internet Corporation for Assigned Names and
  Numbers
• IETF
• The Engineering Task Force
• RFC-Editor
• Request For Comments
• RFC2555, 30 Years of RFCs

5
TCP/IP
Application layer
HTTP
SMTP
DNS
SSH
FTP
Transport layer
TCP
UDP
Network layer
IP
ICMP
IGMP
Hardware Interface
ARP/RARP
Link layer
6
TCP/IP (cont)

• "Be liberal in what you accept, and conservative
  in what you send." Jon Postel (1943-1998)

7
TCP/IP (cont)
HTTP
HTTP
TCP
TCP
The Internet
IP
IP
Ethernet
Ethernet
8
IP Addresses

• IPv4
• 4 bytes, eg. 138.23.169.9
• Network Host portion
• Historical Internet address classes
• A 1-126 N.H.H.H
• B 128-191 N.N.H.H
• C 192-223 N.N.N.H
• D 224-239
• E 240-255

9
IP Addresses (cont)

• Problems
• Class B addresses were running out by 1995
• Routing tables were too big to fit into memory
• Fragmentation
• Solutions
• Short-term
• CIDR Classless Inter-Domain Routing
• Long-term
• IPv6

10
CIDR

• No more classes
• Uses prefix, /00 notation, eg.
• 138.23.0.0/16
• Can be difficult to compute, eg. /26
• Uses http//www.jodies.de/ipcalc

11
IPv6

• 16 bytes
• 128 bits
• Consume more memory on routers?
• Ready for years but too costly to deploy

12
IP Address Allocation

• ICANN delegates blocks of addresses to 5 regional
  Internet registries
• ARIN
• APNIC
• RIPE
• AfriNIC
• LACNIC

13
NAT

• Network Address Translation
• Translation private IP addresses into public
• Private IP addresses (RFC1918)
• A 10.0.0.1/8
• B 172.16.0.0/12
• C 192.168.0.0/16
• Its a hack but it works
• Some researchers hate it since it breaks e2e

14
Hostname and IP Address Assignment

• /etc/hosts
• 127.0.0.1 localhost
• 138.23.169.9 eon.cs.ucr.edu eon
• DNS
• Domain Name System
• DHCP
• Dynamic Host Configuration Protocol

15
Hostname and IP Address Assignment (cont)

• /bin/hostname
• Set or display current hostname
• /bin/ifconfig
• Enable and disable a network interface
• ifconfig eth0 up
• ifconfig eth0 down
• Set IP address, subnet mask, broadcast address
• ifconfig eth0 138.23.169.9 netmask
  255.255.255.128
• ifconfig eth0
• ifconfig -a

16
Routing vs Forwarding

• Routing
• A process to build up a routing table
• Forwarding
• A process to forward packets from one NIC to
  another by consulting the routing table
• Routing table
• netstat -rn
• Kernel IP routing table
• Destination Gateway Genmask
  Flags MSS Window irtt Iface
• 192.168.0.0 0.0.0.0 255.255.255.0 U
  0 0 0 eth0
• 169.254.0.0 0.0.0.0 255.255.0.0
  U 0 0 0 eth0
• 0.0.0.0 192.168.0.1 0.0.0.0
  UG 0 0 0 eth0

17
Reference

• LAH
• Ch 12 TCP/IP Networking