Overview of TCP/IP. TCP/IP and Internet

Transcription

1 Overview of TCP/IP System Administrators and network administrators Why networking - communication Why TCP/IP Provides interoperable communications between all types of hardware and all kinds of operating systems. What is TCP/IP An entire suite of data communication protocols, Transmission Control Protocol (TCP) and the Internet Protocol (IP) are two of those protocols in the suite Overview of TCP/IP 1 TCP/IP and Internet 1969 ARPAnet Experimental packet-switching network Study robust, reliable, vendor-independent data communication Very successful 1975 ARPAnet became operation network Development continuing Basic TCP/IP was developed since then 1983 TCP/IP protocols were adopted as Military Standards TCP/IP was implemented in Berkeley Unix. ARPAnet was divided into MILNET and ARPAnet Overview of TCP/IP 2 1

2 TCP/IP and Internet 1985 NSFNet Linked together the five NSF super computer centers Connected to the then existing Internet ( MILNET plus ARPAnet) Brought a new vision - extend the network to every scientist and engineer 1987 new NSFNet backbone Faster Three-tiered topology: backbone, regional networks, and networks. Overview of TCP/IP 3 TCP/IP and Internet 1985 NSFNet Linked together the five NSF super computer centers Connected to the then existing Internet ( MILNET plus ARPAnet) Brought a new vision - extend the network to every scientist and engineer 1987 new NSFNet backbone Faster Three-tiered topology: backbone, regional networks, and networks. Overview of TCP/IP 4 2

3 TCP/IP and Internet 1990 ARPAnet passed out of existence 1995 NSFNet ceased its role as a primary Internet backbone network Today Internet is build by commercial providers. Infrastructure National network provider - tier-one providers Regional network provider tier-two providers Network Access points (NAPS) Local access and user services Overview of TCP/IP 5 TCP/IP and Internet 1990 ARPAnet passed out of existence 1995 NSFNet ceased its role as a primary Internet backbone network Today Internet is build by commercial providers. Infrastructure National network provider - tier-one providers Regional network provider tier-two providers Network Access points (NAPS) Local access and user services Overview of TCP/IP 6 3

4 Internet structure: network of networks roughly hierarchical at center: tier-1 s (e.g., UUNet, BBN/Genuity, Sprint, AT&T), national/international coverage treat each other as equals Tier-1 providers interconnect (peer) privately Tier 1 NAP Tier 1 Tier 1 Tier-1 providers also interconnect at public network access points (NAPs) Overview of TCP/IP 7 Tier-1 : e.g., Sprint Sprint US backbone network Overview of TCP/IP 8 4

5 Tier-1 : e.g., UUNET UUNET Backbone Connectivity Overview of TCP/IP 9 Internet structure: network of networks Tier-2 s: smaller (often regional) s Connect to one or more tier-1 s, possibly other tier-2 s Tier-2 pays tier-1 for connectivity to rest of Internet tier-2 is customer of tier-1 provider Tier-2 Tier-2 Tier 1 NAP Tier 1 Tier 1 Tier-2 s also peer privately with each other, interconnect at NAP Tier-2 Tier-2 Tier-2 Overview of TCP/IP 10 5

6 Internet structure: network of networks Tier-3 s and s last hop ( access ) network (closest to end systems) Local and tier- 3 s are customers of higher tier s connecting them to rest of Internet Tier 3 Tier-2 Tier 1 Tier-2 Tier 1 Tier-2 NAP Tier 1 Tier-2 Tier-2 Overview of TCP/IP 11 Internet structure: network of networks a packet passes through many networks! Tier 3 Tier-2 Tier 1 Tier-2 NAP Tier 1 Tier-2 Tier 1 Tier-2 Tier-2 Overview of TCP/IP 12 6

7 TCP/IP and the Internet Internet has evolved From a simple backbone network Through a three-tiered hierarchical structure To a huge network of interconnected, distributed network hubs. Doubling in size every year since 1983 est. 50 million host, 100 million+ users One thing remained constant: Internet is build on the TCP/IP protocol. Overview of TCP/IP 13 TCP/IP and the Internet The growth of the Internet spurred interest in TCP/IP it is popular. network applications , html, http, instant messaging, games Other networks Local area networking even not connected to Internet. Enterprise networks intranets. Overview of TCP/IP 14 7

8 TCP/IP Features TCP/IP met the need at the right time. Open protocol standards Free Developed independently from any specific computer hardware or operating system Independence from specific physical network hardware. Ethernet DSL connection Dial-up line Optical network Virtually any other kind of transmission medium. Overview of TCP/IP 15 TCP/IP Features Common addressing scheme allow uniquely address any device in the entire network. Standardized high-level protocols for consistent, widely available user services. Overview of TCP/IP 16 8

9 Protocol Standards What is protocol? Formal rules of behavior. Internet Standards are developed by Internet Engineering Task Force (IETE) in open, public meetings. Requests for Comments (RFCs) Standards (STD) Best current practices (BCP) Informational (FYI) Overview of TCP/IP 17 Protocol Standards Official Internet standard is rigorous Proposed Standard Draft Standard At least two interoperable implementations Internet Standard Extensive testing Significant benefit to the internet community. Overview of TCP/IP 18 9

10 Protocol Standards Two categories of standards Technical Specification defines a protocol Applicability Statement defines when the protocol is to be used. Required Recommended Elective More than 5000 RFCs. Overview of TCP/IP 19 Internet protocol stack application: supporting network applications FTP, SMTP, HTTP transport: host-host data transfer TCP, UDP Internet: defines the datagram and handles the routing of data. IP, routing protocols Network Access Layer: Consist of routines for accessing physical network. PPP, Ethernet Application Transport Internet Network Access Overview of TCP/IP 20 10

11 Internet protocol stack Application: supporting network applications FTP, SMTP, HTTP Transport: host-host data transfer TCP, UDP Internet: defines the datagram and handles the routing of data. IP, routing protocols Network Access Layer: Consist of routines for accessing physical network. PPP, Ethernet Application Transport Internet Network Access Overview of TCP/IP 21 Internet protocol stack Application Layer Data Transport Layer Header Data Internet Layer Header Header Data Network Access Layer Header Header Header Data Overview of TCP/IP 22 11

12 Network Access Layer Provide the means to deliver data to other devices on a directly attached network Functions: Encapsulation of IP datagram to frame Mapping IP addresses to physical addresses. RFC 826: Address Resolution Protocol (ARP) Overview of TCP/IP 23 Internet Layer Internet Protocol (IP) is the most important in this layer IPv4 and IPv6 Main functions Moving data between Network Access Layer and the Transport Layer Routing the datagram to remote hosts Performing fragmentation and re-assembly of datagrams. IP is connectionless protocol No handshaking to establish end-to-end connection IP is called unreliable protocol no error detection and error recovery Overview of TCP/IP 24 12

13 The Datagram Format Version Time to Live IHL Identification Protocol Type of Service flags Source Address Total Length Destination Address Fragmentation offset Header Checksum 6 Options Padding Data begins here Overview of TCP/IP 25 IP IP delivers by checking destination address Host on same network, deliver directly Otherwise, routing via gateway Routing datagrams Host -> gateway -> gateway -> host Overview of TCP/IP 26 13

14 IP Fragmenting datagrams Maximum transmission unit (MTU) for each type of network If the datagram received from one network is longer than the other network s MTU, it must be divided into smaller fragments. Header word 2 contains info that identifies which datagram and info how to re-assemble them Identification what datagram the fragment belongs to Offset what piece of the datagram Flag more fragments bit Passing datagrams to the transport layer Done by using protocol number from word3 Overview of TCP/IP 27 Internet Control Message Protocol (ICMP) Part of internet layer Uses the IP datagram delivery facility to send message Functions Flow control ICMP Source Quench Message, ask source to stop sending temporarily Detecting unreachable destinations Destination Unreachable Message for host and port Redirecting routes To tell a host to use another gateway Checking remote hosts ICMP Echo Message - ping Overview of TCP/IP 28 14

15 Transport Layer Two most important protocol Transmission Control Protocol (TCP) Reliable data delivery User Datagram Protocol (UDP) Connectionless datagram delivery Unreliable Overview of TCP/IP 29 UDP No techniques in the protocol to verify data reached the other end Why use UDP? Low-overhead for small data Query-response model application Application provide their own techniques for reliable data delivery bits Source Port Destination Port Length Checksum Data begins here Figure: UDP Message format Overview of TCP/IP 30 15

16 TCP Reliable Positive Acknowledgment with Retransmission (PAR) connection-oriented Establish a logical end-toend connection Three-way Handshake before data is transmitted Host A Host B SYN SYN,ACK ACK,data Overview of TCP/IP 31 TCP Byte-stream data TCP views data as continuous stream of bytes Sequence Number and Acknowledgement Number keep track of the bytes Exchanging initial sequence number (ISN) random number First byte of data has Sequence number ISN+1 Sequence number identifies the sequential position in the data stream of the first data byte in the segment. Acknowledgment Segment (ACK) Positive acknowledgement Flow control - window Overview of TCP/IP 32 16

17 TCP segment format Source Port Sequence Number Acknowledgement number Destination port Data Offset Reserved Flags Window Checksum Urgent Pointer Options Padding Data begins here See the flags definition: Overview of TCP/IP 33 Application Layer Many application protocols telnet Remote login over network ftp File transfer protocol for transferring files between hosts SMTP Simple Mail Transfer protocol, which delivers electronic mail HTTP Hypertext transfer protocol, delivers web pages over the network. Overview of TCP/IP 34 17

18 Application Layer More application protocols Domain Name System (DNS) Map IP addresses to the names assigned to network devices. Open Shortest Path First (OSPF) Allow network device to exchange routing information Network File System (NFS) Allows files to be shared by various hosts. Overview of TCP/IP 35 Summary We ve talked about TCP/IP and Internet TCP/IP four layers: applications, transport, Internet and Network Access. Next, we will look in detail how IP datagram moves through a network when data is delivered between hosts. Overview of TCP/IP 36 18