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Basic TCP/IP Networking

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.

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Basic TCP/IP Networking

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  1. Basic TCP/IP Networking WeeSan Lee <weesan@cs.ucr.edu> 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 FTP SSH SMTP DNS Transport layer TCP UDP Network layer ICMP IP IGMP ARP/RARP Hardware Interface 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 • It’s 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

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