Types of Transfer. Connection-oriented Transfer. Connectionless Transfer. Networks generally provide two types of communication. Connection-oriented

Transcription

1 Types of Transfer Networks generally provide two types of communication Connection-oriented reliable stream based Connectionless unreliable datagram based CSCI Networking Connection-oriented Transfer Server Accept Connection Establishment Client Connect Communication CSCI Networking 2 Connectionless Transfer Server Client Communication CSCI Networking 3

2 IP: Internet Protocol IP is the workhorse protocol of the TCP/IP protocol suite IP provides an unreliable, connectionless, datagram delivery service RFC79 is the official specification of IP CSCI Networking 4 The Workhorse application TCP UDP transport ICMP IP IGMP network ARP Hardware Interface RARP link CSCI Networking 5 Addressing A distinction is made between names, addresses, and routes A name indicates what we seek An address indicates where it is A route indicates how to get there The internet protocol deals primarily with addresses. It is the task of higher level protocols to make the mapping from names to addresses. CSCI Networking 6 2

3 IP Addresses Every interface on the internet must have a unique Internet Address (also called an IP address) IP addresses are 32-bits numbers The addresses are not flat, they are divided into two components: the host address and the network address The number of bits assigned to the host portion and network portion of the address varies depending on the class of the address CSCI Networking 7 Class A IP Address Classes 7 bits 24 bits netid hostid 4 bits 6 bits Class B netid hostid 2 bits 8 bits Class C netid hostid 28 bits Class D multicast group ID 27 bits Class E (reserved for future use) CSCI Networking 8 Dotted Decimal Notation IP addresses are normally written as four decimal numbers, one for each byte of the address Class Range A... to B to C to D to E to CSCI Networking 9 3

4 Assigning IP Addresses Since every interface must have a unique IP address, there must be a central authority for assigning numbers That authority is the Internet Network Information Center, called the InterNIC. The InterNIC assigns only network ids, the assignment of host ids is up to the system administrator CSCI Networking DNS DNS (Domain Name System), a database that is used by TCP/IP applications to map machine names to IP addresses No single site on the Internet knows all the information, each site maintains its own database of information and runs a server program that other systems across the Internet can query. RFC34 and RFC 35 describe DNS. CSCI Networking DNS Basics DNS breaks the Internet into domains Within each domain there is an administrator who is responsible for assigning names within that domain The domains in DNS are hierarchical A complete DNS names includes all of the names in the path from the top-level domain down to the domain in which the machine resides CSCI Networking 2 4

5 The Top-Level Domains Domain Description com Commercial Organizations edu Educational Institutions gov US Government Organizations mil US Military Organizations int International Organizations net Networks org Other Organizations xx all the 2-letter country codes from the list of countries in ISO-366. CSCI Networking 3 The Generic Domains Even though the original intention was that any educational institution anywhere in the world could be registered under the EDU domain, in practice, it turned out with few exceptions, only those in the US have registered under EDU This is basically the same in the other top-level domains with the exception of GOV and MIL. CSCI Networking 4 The Country Domains In other countries, everything is registered under the 2-letter country code, often with some subdivision. For example, in Korea (KR) the second level names are AC for academic community, CO for commercial, GO for government, and RE for research. However, each country may go its own way about organizing its domain. CSCI Networking 5 5

6 The US Domain Because organizations in the US have registered primarily in the EDU and COM domains, the US domain was rarely used. The US Domain has grown and includes: federal, state, country and city government agencies, K2 schools, community colleges, technical/vocational schools, private schools, and libraries. CSCI Networking 6 The US Domain The US Domain is based on political geography. A basic name under US is the state name, then the "locality" name, (like a city, or county) then organization or computer name and so on. Special names are used: FED, STATE, AGENCY, DISTRICT, K2, LIB, CC, CITY, and COUNTY. CSCI Networking 7 Transmission Control Protocol TCP provides a connection-oriented, reliable, byte stream service (RFC793) TCP is an independent, general purpose protocol that can be adapted for use with delivery systems other than IP. The term connection-oriented means that two applications using TCP must establish a TCP connection with each other before they can exchange data. CSCI Networking 8 6

7 TCP Ports TCP uses protocol port numbers to identify the ultimate destination within a machine. TCP uses the connection, not the protocol port, as its fundamental abstraction; connections are identified by a pair of endpoints. For example, ( , 69) and ( ,). Because a connection is identified by a pair of endpoints, a given TCP port number can be shared by multiple connections on the same machine. CSCI Networking 9 Datagram Protocol UDP is a simple, unreliable, datagramoriented, transport layer protocol (RFC768) bit source port 6-bit length 6-bit destination port 6-bit checksum 8 bytes data (if any) CSCI Networking 2 7