T ODAY I NTERNET A DDRESSING TCIP/IP NAT, IP, TCP, UDP, C ONFIGURATION, DNS, DHCP, WINS L AB 8: C ONFIGURE DHCP S ERVER

N ETWORK A DDRESS T RANSLATION (NAT) Allows unregistered private network addresses to communicate with legally registered IP addresses Advantages Hides internal IP addresses, thus providing security Eliminates need for multiple registered IP addresses Allows multiple ISDN (Integrated Services Digital Network) connections to be combined into one Internet connection

IP C ONFIGURATION

D OMAIN N AME S YSTEM (DNS) Makes it easy to identify and find hosts on Internet When domain name is entered, it is converted to its IP address

F ULLY Q UALIFIED D OMAIN N AME (FQDN) Needed to locate a host on a large network Example of an FQDN: station2.xyzcorp.com *A combination of the host name and domain name. Operating systems such as Linux, and Windows 2000 and later follow the rules of Fully Qualified Domain Names when creating their network structure.

(FQDN VS N ET B IOS N AME ) Fully Qualified Domain Name is limited to 63 characters. NetBIOS names is a computer name limited to 15 characters. Many symbols allowed in NetBIOS names cannot be used in FQDN. (;:”<>*+=\/?,) To allow for communication between legacy systems and ones that use host names the computer names are converted automatically.

DNS S TRUCTURE AND O PERATION Hierarchical structure Root - The authoritative name servers that serve the DNS root zone Top-level domains—.com,.edu,.gov,.net,.org Second-level domains—mit.edu Subdomains(any level domain located beneath the secondary domain)— campus.mit.edu, faculty.mit.edu Subdomains AKA (lower-level domain)

DNS S TRUCTURE AND O PERATION ResolverResolver A software program located on a host that queries a DNS server to resolve a host name to an IP address Research.mit.edu DNS server the host is connected to as part of a workgroup or domain. OR it could be an ISP Domain names are placed in cache for future requests. If not in cache Top level DNS is contacted root sever If top level server cannot resolve request it is passed on to the root sever Once information is found it is returned to the resolver

W INDOWS I NTERNET N AMING S ERVICE (WINS) Windows NT server operating systems used WINS to resolve NetBIOS names to IP addresses Windows 2000 and later use the Dynamic DNS, which incorporates the WINS and DNS features

IP, TCP, AND UDP Three most commonly used protocols in TCP/IP suite IP establishes a link between nodes but does not verify the data is delivered correctly – connectionless protocol TCP ensures packets arrive intact and in correct order - connection-oriented TCP can break large amounts of data into smaller packets and UDP cannot UDP sends a single packet to transmit control information and data - connectionless protocol

TCP OR UDP The selection of TCP or UDP depends on three factors The software used in the upper layers of the OSI model The amount of data to be sent If a connectionless or connection- oriented transport of data is desired

OSI M ODEL AND TCP/IP

UDP F RAME UDP and TCP Rely on the IP Frame format for IP address Destination and source Used to transfer small blocks of data and commands

TCP F RAME Used to reassemble data in a correct order

IP F RAME Final step is to encapsulate the entire set of protocol frames in a frame matching the network standard e.g Ethernet

A SSIGNING IP A DDRESSES Static addressingStatic addressing or dynamic addressing can be used to assign IP addresses to hostsdynamic addressing A static IP assignment is entered manually when the NIC is configuredstatic IP assignment A server running the Dynamic Host Configuration Protocol (DHCP) issues an IP address to a host when it joins the networkDynamic Host Configuration Protocol (DHCP) (dynamic IP assignment) an IP address that is issued automatically. Typically when a computer boots and joins the network.dynamic IP assignment The default DHCP IP lease period is 8 days.

D YNAMIC A DDRESSING

A UTOMATIC P RIVATE IP A DDRESSING (APIPA) Used when the host is unable to access a DHCP server Host automatically generates an IP address in the range of to Uses the APIPA address to communicate with other workstations on the same segment. This addressing is compatible with all Microsoft products starting with Windows 98 This was not necessary in previous operating systems due to NetBEUI protocol which uses MAC addresses to communicate with workstations on the same segment

TCP/IP P ORTS AND S OCKET A port number combined with an IP address (socket) is used to create a virtual connectionport numbersocket E.G :80 Socket technology allows multiple, simultaneous services to run between a server and a workstation.

E XAMPLES OF W ELL -K NOWN P ORT N UMBERS Service or ProtocolPort Number FTP20, 21 SSH22 Telnet23 SMTP25 DNS53 TFTP69 HTTP80 POP3110 NNTP119 NTP123 IMAP4143 HTTPS443