1. Overview of TCP/IP1-1 Overview of TCP/IP  System Administrators and network administrators  Why networking - communication  Why TCP/IP m Provides interoperable communications between all types of hardware and all kinds of operating systems.  What is TCP/IP m An entire suite of data communication protocols, m Transmission Control Protocol (TCP) and the Internet Protocol (IP) are two of those protocols in the suite

2. Overview of TCP/IP1-2 TCP/IP and Internet  1969 ARPAnet m Experimental packet-switching network m Study robust, reliable, vendor-independent data communication m Very successful  1975 ARPAnet became operation network m Development continuing m TCP/IP was developed  1983 TCP/IP protocols were adopted as Military Standards m TCP/IP was implemented in Berkeley Unix. m ARPAnet was divided into MILNET and ARPAnet

3. Overview of TCP/IP1-3 TCP/IP and Internet  1985 NSFNet m Connected to the then existing Internet ( MILNET plus ARPAnet) m Linked together the five NSF super computer centers m Wanted to extend the network to every scientist  1987 new NSFNet backbone m Faster m Three-tiered topology: backbone, regional networks, and local networks.

4. Overview of TCP/IP1-4 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. m Infrastructure is being created by National network provider, caller tier-one providers Regional network provider m Local access and user services is provided by Internet Service Providers (ISPs) m Network Access Points (NAPS): major interconnection points

5. Overview of TCP/IP1-5 Internet structure: network of networks  roughly hierarchical  at center: “tier-1” ISPs (e.g., UUNet, BBN/Genuity, Sprint, AT&T), national/international coverage m treat each other as equals Tier 1 ISP Tier-1 providers interconnect (peer) privately NAP Tier-1 providers also interconnect at public network access points (NAPs)

6. Overview of TCP/IP1-6 Tier-1 ISP: e.g., Sprint Sprint US backbone network

7. Overview of TCP/IP1-7 Tier-1 ISP: e.g., UUNET UUNET Backbone Connectivity

8. Overview of TCP/IP1-8 Internet structure: network of networks  “Tier-2” ISPs: smaller (often regional) ISPs m Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs Tier 1 ISP NAP Tier-2 ISP Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet  tier-2 ISP is customer of tier-1 provider Tier-2 ISPs also peer privately with each other, interconnect at NAP

9. Overview of TCP/IP1-9 Tier-2 ISP: e.g., Abilene (Internet2) http://loadrunner.uits.iu.edu/weathermaps/abilene/abilene.html

10. Overview of TCP/IP1-10 Internet structure: network of networks  “Tier-3” ISPs and local ISPs m last hop (“access”) network (closest to end systems) Tier 1 ISP NAP Tier-2 ISP local ISP local ISP local ISP local ISP local ISP Tier 3 ISP local ISP local ISP local ISP Local and tier- 3 ISPs are customers of higher tier ISPs connecting them to rest of Internet

11. Overview of TCP/IP1-11 Internet structure: network of networks  a packet passes through many networks! Tier 1 ISP NAP Tier-2 ISP local ISP local ISP local ISP local ISP local ISP Tier 3 ISP local ISP local ISP local ISP

12. Overview of TCP/IP1-12 TCP/IP and the Internet  Internet has evolved m From a simple backbone network m Through a three-tiered hierarchical structure m 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: m Internet is build on the TCP/IP protocol.  The growth of the Internet spurred interest in TCP/IP – it is popular. m Other network applications, email, html, http, Mosaic,instant messaging, games m Local area networking even not connected to Internet. m Enterprise networks intranets.

13. Overview of TCP/IP1-13 TCP/IP Features  TCP/IP met the need at the right time.  Open protocol standards m Free m Developed independently from any specific computer hardware or operating system  Independence from specific physical network hardware. m Ethernet m DSL connection m Dial-up line m Optical network Virtually any other kind of transmission medium.

14. Overview of TCP/IP1-14 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.

15. Overview of TCP/IP1-15 Protocol Standards  What is protocol? m Formal rules of behavior.  Internet Standards are developed by Internet Engineering Task Force (IETE) in open, public meetings.  Requests for Comments (RFCs) m Standards (STD) m Best current practices (BCP) m Informational (FYI)  Official Internet standard is rigorous m Proposed Standard m Draft Standard At least two interoperable implementations m Internet Standard Extensive testing Significant benefit to the internet community.

16. Overview of TCP/IP1-16 Protocol Standards  Two categories m Technical Specification – defines a protocol m Applicability Statement – defines when the protocol is to be used. Required Recommended Elective  More than 3000 RFCs.

17. Overview of TCP/IP1-17 Internet protocol stack  application: supporting network applications m FTP, SMTP, HTTP  transport: host-host data transfer m 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

18. Overview of TCP/IP1-18 Internet protocol stack Application Layer: Data  Header Data Transport LayerHeader:Header Data   Internet Layer:Header Header Data   Network Access Layer:Header Header Header Data

19. Overview of TCP/IP1-19 Network Access Layer  provide the means to deliver data to other device  Encompass functions of Network, Datalink and Physical in OSI Reference Model  Many access protocol – one for each physical network. New hardware needs new protocol. Typically show as device drivers and related programs.  Functions:  Encapsulation of IP datagrams to frames  Mapping IP addresses to physical addresses.

20. Overview of TCP/IP1-20 Internet Layer  Internet Protocol (IP) is the most important in this layer  IPv4 and IPv6  Internet Protocol Functions m Defining the datagram m Defining the Internet addressing scheme m Moving data between Network Access Layer and the Transport Layer m Routing datagrams to remote hosts m Performing fragmentation and re-assembly of datagrams.  IP is connectionless protocol  IP depends on other layers to do error detection and error recovery – some time called unreliable protocol

21. Overview of TCP/IP1-21 The Datagram VersionIHLType of Service Total Length IdentificationflagsFragmentation offset Time to Live ProtocolHerder Checksum Source Address Destination Address OptionsPadding Data begins here IP datagram format 123456123456

22. Overview of TCP/IP1-22 Datagrams  IP delivers by checking destination address m Host on same network, diver directly m Otherwise, routing via gateway  Routing datagrams m Host -> gateway -> gateway … -> host  Fragmenting datagrams m Maxium transmission unit (MTU) for each type of network m If the datagram received from one network is longer than the other network’s MTU, it must be divided into smaller fragments. m 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

23. Overview of TCP/IP1-23  Passing datagrams to the transport layer m Done by using protocol number from word3  Internet Control Message Protocol (ICMP) m Part of internet layer m Uses the IP datagram delivery facility to send message m 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 – ICMP Redirect Message Checking remote hosts – ICMP Echo Message –Ping

24. Overview of TCP/IP1-24 Transport Layer  Two most important protocal m Transition Control Protocol (TCP) Reliable data delivery m User Datagram Protocol (UDP) Low-overhead, connectionless datagram delivery  UDP m No techniques in the protocol to verify data reached the other end m 16-bit sort port and destination port m Why use UDP? Small data Query-response model application Application provide their own techniques for reliable data delivery

25. Overview of TCP/IP1-25 Transport Layer  UDP Message format Source PortDestination Port LengthChecksum Data begins here 0 16 31

26. Overview of TCP/IP1-26 Transport Layer  TCP m Reliable Positive Acknowledgment with Retransmission (PAR) m connection-oriented Establish a logical end-to-end connection Three-way Handshake before data is transmitted Host A Host B SYN SYN,ACK ACK,data

27. Overview of TCP/IP1-27 Transport Layer  TCP m 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. m Acknowledgment Segment (ACK) Positive acknowledgement Flow control - window

28. Overview of TCP/IP1-28 Transport Layer  TCP segment format Source PortDestination port Sequence Number Acknowledgement number OffsetReservedFlagsWindow ChecksumUrgent Pointer OptionsPadding Data begins here 0 16 31

29. Overview of TCP/IP1-29 Application Layer  Included all processes that use the Transport Layer protocols to deliver data m telnet Remote login over network m ftp File transfer protocol for transferring files between hosts m SMTP Simple Mail Transfer protocol, which delivers electronic mail m HTTP Hypertext transfer protocol, delivers web pages over the network. m Domain Name System (DNS) Map IP addresses to the names assigned to network devices.

30. Overview of TCP/IP1-30 Application Layer m Network File System (NFS) Allows files to be shared by various hosts. m Programming network application: socket API

31. Overview of TCP/IP1-31 Summary We’ve talked about  TCP/IP and Internet  TCP/IP four layers: applications, transport, Internet and Network Access. Next, we will look how IP datagram moves through a network when data is delivered between hosts.