Basic TCP/IP Networking WeeSan Lee <weesan@cs.ucr.edu> http://www.cs.ucr.edu/~weesan/cs183/

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

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

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

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

TCP/IP (cont) "Be liberal in what you accept, and conservative in what you send." – Jon Postel (1943-1998)

TCP/IP (cont) HTTP HTTP TCP TCP The Internet IP IP Ethernet Ethernet

IP Addresses IPv4 Historical Internet address classes 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

IP Addresses (cont) Problems Solutions 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

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

IPv6 16 bytes Consume more memory on routers? 128 bits Consume more memory on routers? Ready for years but too costly to deploy

IP Address Allocation ICANN delegates blocks of addresses to 5 regional Internet registries ARIN APNIC RIPE AfriNIC LACNIC

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 It’s a hack but it works Some researchers hate it since it breaks e2e

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

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

Routing vs Forwarding Routing Forwarding Routing table 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

Reference LAH Ch 12: TCP/IP Networking