What is TCP/IP?

• TCP/IP is Transmission Control Protocol/Internet Protocol.

• A protocol is a definition for communication on a network.

• IP, Internet Protocol is the basic set of rules for talking on the Internet.

• TCP/IP has been a standard since 1983.

• TCP/IP is one of the three major protocols at UF---the others are IPX (Netware) and Appletalk for Macs.

• All types of desktop computers (Mac, UNIX, PC) can use TCP/IP.

TCP/IP is many protocols

There are many application protocols that are specialized versions of TCP/IP and require TCP/IP.

telnet

Network Terminal Protocol.

ftp

File Transfer Protocol.

smtp

Simple Mail Transfer Protocol. The UF standard for inter-system mail delivery.

bootp

Boot Parameters Protocol. Convenient protocol for maintaining PCs.

http

Hypertext Transport Protocol. The protocol used by the World Wide Web.

nntp

Network News Transport Protocol. The Usenet protocol.

DNS

Domain Name Service.

ntp

Network Time Protocol.

arp

Address Resolution Protocol.

POP

Post Office Protocol.

SLIP

Serial Line IP Protocol.

RIP

Routing Information Protocol.

NFS

Network File System Protocol.

NIS

Network Information System Protocol.

TCP/IP based applications

Email

Electronic mail. Usually simple text, but voice/video/graphics via MIME.

News

5800+ active discussion groups.

telnet

Logging on to Internet computers.

ftp

File transfer between Internet computers.

The Web

Hypertext across the Internet.

lpr

Remote printing.

ph

Phone book.

Names and Addresses

Messages are subdivided into packets (datagrams). Each packet is addressed. Humans use names to address streams of packets. Machines use numbers (IP numbers).

Packets are reassembled at the destination. Missing packets are resent. Jumbled packets are reordered.

Names

Every machine (destination) has a name. At UF the names have the format:

machine.domain .ufl.edu

The ufl.edu part is fixed. The domain name is chosen to organize collections of machines by department or college.

The machine name is chosen by the owner (maybe). See RFC 1178 for good tips on naming.

Some PCs and Macs may not have names (they may not be destinations).

Names are turned into addresses by domain name service. DNS is done by name server computers.

Addresses

Addresses are also known as IP numbers. IP numbers at UF have the format:

128.227.subnet.machine

128.227 is UF's Class B network address assigned to us by NIC.

The subnet number is in the range 1-254 and denotes a particular wire or wires containing individual machines.

The machine number is also in the range 1-254. No more than 254 machines on a subnet.

So UF's theoretical maximum # of networked computers is . We currently have over 3,000.

Subnets

Subnets may contain multiple domains.

Domains may span many subnets.

Subnets at UF are assigned by Dave Pokorney and Rick Smith.

IP numbers on a subnet are assigned by the subnet administrator, or block administrator.

IP numbers MUST be registered! Either with NERDC at

update@name.server.ufl.edu

or with the block or subnet administrator.

Routers (IP gateways) determine which subnets are on which wires.

HEALTHNET Internet Routing Diagram

Domain Name Service

Domain Name Service is the Internet standard method for associating the names of computers with their IP numbers. Forward pointers are used to return numbers given names. Reverse pointers are used to return names given numbers.

When IP numbers are assigned to machines, the pair of name and number are registered with the domain name server for that domain (forward pointer) and the domain name server for that subnet (reverse pointer). These machines need not be the same.

If names and numbers are not registered properly, requests for services by name will fail and requests for names by number will fail.

The names and numbers in use within domain can be found using the dns page provided by CLAS. The page can also be used to get lists of the machines registered with domain name service on each subnet.

Setting up TCP/IP at UF

To set up a machine using TCP/IP networking, you will need software, you will need to know several addresses, and you will need to indicate how machines on subnets are addressed.

Macs use MacTCP (built-in with System 7.5). UNIX machines have built-in TCP/IP support. PCs can use Lan WorkPlace from Novell, which includes several TCP/IP applications. Windows '95 has built-in TCP/IP support, and SLIP support for remote access.

You will need to know the machine's IP number, it's broadcast address, it's gateway address, your subnet mask and your name server address.

Your IP number

Your IP number has the form

128.227.subnet.machine

The subnet number is determined by the machine's physical location. This is called geographic routing.

The machine number is assigned by the subnet or block administrator and registered in domain name service.

You may be able to get a block of IP numbers from the subnet administrator and then assign them as you see fit, registering each as you assign it.

Broadcast Address

All broadcast addresses on the UF Class B have the form:

128.227.subnet.255

The broadcast address is used to send packets to all machines on the subnet. These packets contain queries such as "Who here has IP #?"

Gateway Address

Almost all gateway addresses at UF have the form:

128.227.subnet.1

The gateway address is the IP number of the gateway (router) that connects your subnet to the rest of the UFNET.

Subnet Mask

The subnet mask defines how machines are addressed on the subnet. Since UF is a Class B network and we use the third octet for a subnet number and the fourth octet for a machine number, the subnet mask at UF is:

255.255.255.0

Name Server Addresses

The name server address(es) (1 or more) are the IP numbers of the machines that can turn names into IP numbers. The campus name servers are:

  128.227.104.125       net.health.ufl.edu
  128.227.128.024       name.server.ufl.edu
  128.227.148.252       cutter.clas.ufl.edu
  192.080.214.100       noc.sura.net

Reference

Hunt, C (1992) TCP/IP Network Administration, Sebastopol, CA: O'Reilly and Assoc., 471 pages.

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