Chapter Eleven An Introduction to TCP/IP
Objectives • To compare TCP/IP’s layered structure to OSI • To review the structure of an IP address • To look at some of the different protocols in the suite • To learn a bit about address translation in TCP/IP
TCP/IP and Layers • TCP/IP has four layers • Compared to OSI’s seven layers • For the most part, map cleanly to OSI layers
The Four TCP/IP Layers • Process/Application • Host-to-Host • Internet • Network Access
Reviewing IP Address Structure • IPv4 uses a 32-bit address. • IPv6 uses a 128-bit address. • IPv4 addresses are broken down into classes. • One address identifies both the network and host address. • A subnet mask separates the network portion from the host portion of the address.
IP Address Classes • Class A • 1 octet for network, 3 for host • Class B • 2 octets for network, 2 for host • Class C • 3 octets for network, 1 for host • Class D – multicasts • Class E – experimental
TCP/IP Protocol Suite • Different protocols work at different layers. • Different functions exist at each protocol layer. • No protocols exist at the Network Access layer that I will discuss here.
Process Application Protocols • FTP/TFTP • HTTP • Telnet • SMTP/POP • IMAP4 • SNMP • NFS
FTP/TFTP • File Transfer Protocol/Trivial File Transfer Protocol • Both function to transfer complete files over the network • FTP is a connection-oriented protocol • Port 20 for user data and Port 21 for control data • TFTP is a connectionless protocol • Port 69 for user data, no control data passed
HTTP and HTTPS • Hypertext Transfer Protocol and Hypertext Transfer Protocol Secure • Used for interpreting and moving hypermedia over a network • HTTP uses Port 80; HTTPS uses Port 443. • HTTPS uses the secure socket layer (SSL) and encryption algorithms in order to increase security.
Telnet • Creates a virtual terminal on the network • Allows a user to take control of a device remotely • Uses Port 23 • Used by many routers and switches for configuration
SMTP and POP • The protocols of email • Simple Mail Transfer Protocol for outgoing • Post Office Protocol for incoming • SMTP uses Port 25 • POP3 uses Port 110 (older POP2 uses 109)
IMAP4 • Internet Message Access Protocol, Version 4 • A more advanced protocol for sending email messages • Allows users to create and maintain folders on the remote server • Uses Port 220
SNMP • Simple Network Management Protocol • Allows network administrators to gather information about the network and to perform routine maintenance functions remotely • SNMP manager runs on the administrator machine and the agent on the user’s machine • Uses Port 161 for general messages and 162 for trap messages
NFS • Network File System • Allows the network to be browsed like a disk drive • Uses Port 2049
Host-to-Host Protocols • TCP • UDP • DNS
TCP • Transmission Control Protocol • Manages point-to-point movement of data from source to target • Connection-oriented protocol • Handles flow control, multiplexing, data transfer, and error correction/detection
UDP • User Datagram Protocol • Connectionless protocol • Useful for broadcast messages and/or small data packages
DNS • Domain Name Services • Resolves Internet domain names to IP addresses • Acts as the core protocol for active directory
Structure of a DNS Domain Name • The “dot” server • .com, .gov, .org and so on and so forth • The dot points to the DNS root. • A different set of servers, called root servers, maintains database of each type of DNS root. • The top level domain • Country code (.us, .uk, .jp, and so forth) • Generic domains (.com, .gov, .biz, and so forth) • Infrastructure domains (.arpa) the address routing domain
DNS at Work • Each workstation must be configured with the address of a DNS server. • You type in a universal resource locator (URL) and your computer can’t resolve it. • The request is forwarded to the DNS server configured in TCP/IP. • If the DNS server has no record, it forwards the request to the appropriate root server.
Types of DNS Query • Recursive • If the DNS server cannot resolve the request, it will forward it to the next level. • When the next level replies, the server adds the information to its database. • Iterative • The request MUST be fulfilled on the local server. • It responds with all it knows and that’s all she wrote.
Internet Layer Protocols • IP • BootP • DHCP • ICMP • ARP • RARP
IP • Handles addressing between different networks • Provides for fragmentation of data over a network connection • Handles all routing functions • Tracks packet time to live
BootP • It allows a computer to boot up using files that are stored on a remote device. • The bootstrap loader directs its boot request to the boot PROM on the NIC. • The request is forwarded through Port 67. • A BootP server sends back a boot reply packet with the data it needs to locate the boot files.
DHCP • Dynamic Host Configuration Protocol • It configures a client computer with all of its TCP/IP information. • This information is “leased” for a certain time. • DHCP can configure IP address, subnet mask, DNS server, and several other items.
ICMP • Internet Control Message Protocol • Announces network errors • Announces conditions of network congestion • Announces when a packet has timed out • Is the core protocol for PING
ARP • Address Resolution Protocol and Reverse Address Resolution Protocol • ARP sends out a packet to the target device requesting a reply. • The reply has the machine’s IP address and MAC address in the header.
RARP • It requires that RARP server be configured. • A client machine broadcasts its IP address. • The RARP server responds with an IP address.
Address Resolution in TCP/IP • WINS • HOSTS • LMHOSTS
WINS • Windows Internet Name Service • Resolves a NetBIOS name to an IP address • Requires that a WINS server be configured on the network • Is old and graying, but not dead just yet
The HOSTS and LMHOSTS File • Both are text files stored in the root directory. • HOSTS maps a DNS name to an IP address. • LMHOSTS maps a NetBIOS name to an IP address.