1. Chapter 14 TCP/IP and Routing Part #1 Unix System Administration

2. T.C. P’s and I P’s n What is TCP/IP? n TCP/IP is a networking protocol for transmitting data between computers n TCP/IP is a family of protocols n TCP/IP is the protocol of the Internet n TCP/IP is the default protocol of UNIX n TCP/IP provides a uniform programming interface to different types of network hardware that guarantees interoperability

3. We Are Family n IP - Internet Protocol which transports raw data from one machine to another n ICMP - Internet Control Message Protocol provides low-level support for IP such as error messages, routing assistance and “pings” n ARP - Address Resolution Protocol which translates logical address (IP address) to hardware address (MAC address)

4. All in the Family n TCP - Transmission Control Protocol uses IP to maintain a connection- oriented sessions between machines that guarantees delivery of data. n UDP - User Datagram Protocol uses IP for connectionless sessions between machine without the guarantee of data delivery.

5. So You Want to Date a Model? n The OSI Model by the ISO n Seven Layers –Layer 7 - Application Layer –Layer 6 - Presentation Layer –Layer 5 - Session Layer –Layer 4 - Transport Layer –Layer 3 - Network Layer –Layer 2 - Data Link Layer –Layer 1 - Physical Layer

6. The Government Thought OSI Was A Good Idea n The US Government decided all government computers should use OSI n OSI had implementation problems –Relied on concepts that made no sense in modern networks –Some specifications were incomplete –Functionally inferior to existing protocols –Too many layers which made it slow

7. Back to Good Ol’ TCP/IP in the Good Ol’ US of A n Good enough of government work n TCP/IP has 4 layers –Layer 4 - Application Layer (think telnet, ftp, http, etc.) –Layer 3 - Transport Layer (think TCP/UDP) –Layer 2 - Network Layer (think IP) –Layer 1 - Link Layer (think ethernet card)

8. How Does it All Fit Together Exhibit A from Page 246 in your book

9. Pack-et In a Frame n Data travels the network in a packet which consists of a payload and headers n Packets are sometimes referred to as frames when talking about the low-level transport, (e.g. Ethernet) n The low-level transport may limit the size of a frame/packet. This is called the MTU - maximum transfer unit

10. Sample Packet

11. IP on Your MAC Port? n Three key addresses determine the source and destination of a packet –MAC - low-level address of network hardware. For Ethernet, 6-byte globally unique address. –IP - dotted quad-octet assigned to each network device. Globally unique. –Port - two-byte number that specifies a particular service on a machine

12. Mapping IP to MAC Using ARP n The ARP protocol is used to map IP address to MAC addresses –Machine sends ARP request “Who is 159.91.15.220?” –The machine or another machine on the same network will respond “00:40:95:21:CB:38 is 159.91.15.220” –The MAC address is used to make the final delivery of the packet to the destination machine.

13. Dotted? Quad? Octet? n IP Address –Octet = 8-bit number (usually we call this a byte, but old DEC systems used 7-bit bytes) = values 0-255 –octet.octet.octet.octet is the format of an IP address, such as 159.91.15.220 –IP addresses have a structure to their assignment, where as, MAC addresses have no relationship to each other

14. IP Address Have Classes Too n There are 5 classes for IP addresses –Class A - first octet is assigned as the network address, the remaining 3 octets are available for network devices –Class B - first two octets are assigned as the network address, remaining 2 octets are available for network devices –Class C - first three octets are assigned as the network address, remaining octet is available for network devices

15. Going Out With Class n The last two IP classes are special –Class D - multicast addresses. This is the rare case where the multiple machines can have the same IP address –Class E - experimental

16. IP Class Summary

17. Who’s The Head of the Classes? n *NOTE* - the book is out of date about this n Today, you typically get your addresses from your Internet Service Provider n Addresses are ultimately controlled by IANA - Internet Assigned Number Authority. IANA give certain registries around the globe authority to give out IP addresses. www.iana.org n ARIN - American Registry for Internet Numbers handles the Americas. www.arin.net

18. IP Privately n There are private IP addresses set aside for internal use. They are not routed if they get to the Internet. n These private addresses can be used if you setup a standalone network or if you will be using NAT (Network Address Translation) to translate a private address to a valid public address before going to the Internet.

19. Still, IP Privately n RFC1918 –http://www.isi.edu/in-notes/rfc1918.txt –Class A - 10.0.0.0 thru 10.255.255.255 –Class B - 172.16.0.0 thru 172.31.255.255 –Class C - 192.168.0.0 thru 192.168.255.255

20. What Service Do You Use Your Port For? n A port is the location on a particular machine that a service is running on. n Think of it as room in a house. The house has an address (IP), but each room (port) provides a certain function. n Ports below 1024 are called “well known” ports. Only root has access to start services on these ports. n Ports 1024 and above are called “ephemeral” ports. These ports are open to everyone on the system.

21. What’s That In My #2 Port? n Normally, a vendor goes to IANA to get a port assigned to them for their service to run on. Each service has a unique port. E.g. - telnet is 23, http is 80. n RFC1700 used to keep this list, but is now out-dated. n See http://www.iana.org/numbers.html for the most up-to-date list.

22. Why, Why, Y? n Why would you use a private address with NAT when connecting to the Internet instead of getting public addresses for each machine? n Why would you use a multicast (class D) address?

23. Coming Soon to a Lecture Near You n Part #2 - Routing and Subnets