Internet Protocol (IP)

1. Internet Protocol (IP) ITEC 370 George Vaughan Franklin University

2. Sources for Slides • Material in these slides comes primarily from course text, Guide to Networking Essentials,Tomsho, Tittel, Johnson (2007). • Other sources are cited in line and listed in reference section.

3. TCP/IP and OSI Models

4. Subnetting with Classless IP Addressing: Example 1

5. Subnetting with Classless IP Addressing: Example 1 (Continued)

6. Subnet 0 194.10.3.0 - 194.10.3.31 Subnet 1 194.10.3.32 - 194.10.3.63 Subnet 2 194.10.3.64 - 194.10.3.95 Subnet 3 194.10.3.96 - 194.10.3.127 Subnet 4 194.10.3.128 - 194.10.3.159 Subnet 5 194.10.3.160 - 194.10.3.191 Subnet 6 194.10.3.192 - 194.10.3.223 Subnet 7 194.10.3.224 - 194.10.3.255 Network Diagram of Subnets

7. IP Packet Structure(IP Structure, n.d.)

8. IP Packet Structure (Cont.) (IP Structure, n.d.) • Version (4 bits) • IP Version (e,g, IPv4) • IHL (4 bits) • Internet header length in 32 bit words • Minimum length is 5 (32 bit words) • Type of Service (8 bits) • A set of values used to specify desired Quality of Service (QoS). • Total Length (16 bits) • Length of datagram in octets, including header (max 65, 535)

9. IP Packet Structure (Cont.) (IP Structure, n.d.) • Identification (16 bits) • A unique value for sender, receiver to aid in assembling fragments of a datagram • Flags (3 bits) • Fragmentation control flags • Fragment Offset (13 bits) • Fragment position in datagram • Time to Live (8 bits) • Time to live in seconds • Each hop decrements this field be at least 1 (even if less than a second per hop) • Prevents packets from floating around forever in a misconfigured network.

10. IP Packet Structure (Cont.) (IP Structure, n.d.) • Protocol (8 bits) • The upper layer protocol that generated this datagram • Examples: ICMP, TCP, UDP, GRE, etc. • Header Checksum (16 bits) • Used to detect errors in IP header only • Since ‘Time to Die’ changes at each hop, checksum is also recomputed at each hop. • Source IP Address (32 bits) • Destination IP Address (32 bits) • Options (Variable in bit size) • Padding (Variable in bit size) • Enough bits to round out the last word to 32 bits.

11. Internet Protocol (IP) • Network Layer • Supports packet data communication across an internetwork. • Source and Destination logical addressing, routing • IP addresses (not layer 2 MAC addressing) • Connectionless • No circuit setup before use • Fast but not reliable • Best effort delivery

12. Internet Control Message Protocol (ICMP) • Network Layer • Used to send error and control messages • Used by ‘Ping’ utility • Used when ‘Time to Live’ (TTL) value reaches zero • An ICMP message is sent back to the source

13. Address Resolution Protocol (ARP) • Network Layer • Used to resolve logical (IP) address to physical (MAC) address • Can only be used for two systems in same network (subnet).

14. ARP Example • Device A needs to send a message to Device B • Before device A can send message, it needs the following addresses for device B: • IP (logical address) • MAC (physical address) • Device A sends out ARP broadcast message to all devices in same network as Device A. • Device B recognizes IP address in ARP and sends back MAC address to Device A • Device A now has 2 addresses necessary for send message to device B.

15. Transmission Control Protocol (TCP) • Transport Layer • Accepts messages of any length from upper layers • Connection-Oriented • Uses 3-way handshake to establish connection • A sends ‘Synchronize’ (SYN) message to B • B sends ‘Synchronize Acknowledgement’ (SYN-ACK) message back to A • A sends a ‘Forward Acknowledgment’ (ACK) to B • Connection between A and B is now established. • TCP is responsible for fragmenting application into segments • TCP is responsible for reassembling the application data from segments. • TCP uses Acknowledgment messages to: • Ensure that data is properly received. • Manage flow control

16. User Datagram Protocol (UDP) • Transport Layer • Connectionless • Similar to IP, but operates at Transport Layer, therefore, directly accessible to applications • Faster, but less reliable than TCP • UDP itself does not segment application data • UDP does not use acknowledgements • UDP is used by some higher layer protocols such as NFS and DNS.

17. Domain Name System (DNS) • Application Layer • Domain Name-to- IP Address resolution system • Used for translating domain name based URLs and email addresses into IP addresses • einstein.franklin.edu  65.24.7.3 (try ‘nslookup einstein.franklin.edu’) • Once a name has been resolved, it is often cached to limit traffic on Domain Name Servers • Cache has figured value for ‘Time To Live’. • When an IP to Domain Name mapping is changed, it may take on the order of hours for caches to catch up

18. Hypertext Transport Protocol (HTTP) • Application Layer • Web-pages, browsers, servers • Runs on top of TCP

19. File Transfer Protocol (FTP) • Application Layer • Runs on top of TCP • Used to send and/or manipulate text and binary files from one computer to another. • Example FTP Application: WinSCP

20. Telnet Protocol • Application Layer • Runs on top of TCP • Used to establish a remote, text-based session from one computer to another • Example Telnet application: PuTTY.

21. Simple Mail Transport Protocol (SMTP) • Application Layer • Runs on top of TCP • De facto standard protocol for email programs.

22. Dynamic Host Configuration Protocol (DHCP) • Application Layer • UDP Based • Allows a device to obtain a temporary IP address from a DHCP server. • Server must be configured with a block of IP available IP addresses. • In addition to providing a temporary IP address, DHCP can also provide the following information: • Default Gateway • Subnet Mask • Broadcast based protocol sent during boot: • Client leases the address the server assigns to it • If no answer is received, in an APIPA-enabled OS, the computer assigns itself an address (169.254.x.x)

23. Network Address Translation (NAT) • Allows a company to use private IP addresses within the company. • Router maps private IP addresses to a smaller pool of public IP addresses. • Home routers use this technique for private IP addresses such as 192.168.1.x • Also provides security since devices outside of private network can’t see private IP addresses. • NAT has greatly extended the life of IPv4 • IPv4 supports less than 4 billion IP addresses • NAT uses these IP addresses very efficiently.

24. Port Address Translation (PAT) • PAT extends the efficiency of NAT • PAT maps private IP address, port combination to public IP address, public port. • Example: • 192.168.1.3, port 5005 -> 201.35.2.33 port 80 • 192.168.1.4, port 5006 -> 201.35.2.33 port 23 • PAT can allow thousands of workstations to reuse the same IP address. • Ports 1024 through 65535 can be used by router for remapping

25. IP Addressing Tools • Looking up an IP address: • http://psacake.com/web/eg.asp • Subnetting: • http://ccna.exampointers.com/subnet.phtml

26. IPv6 Address Scheme • Hexidecimal grouped in 16 bit sections: • 2001:1b20:302:442a:110:2fea:ac4:2b • Leading zeroes are eliminated • 2 or more 16 bit fields of all zeros can be ignored, as long as there is only one double colon in the address: • 2001:260:0:0:0:2ed3:340:ab (long form) • 2001:260::2ed3:340:ab (short form) • IPv6 has 3 parts:

27. References Tomsho, Tittel, Johnson (2007). Guide to Networking Essentials. Boston: Thompson Course Technology. Odom, Knott (2006). Networking Basics: CCNA 1 Companion Guide. Indianapolis: Cisco Press Wikipedia (n.d.). OSI Model. Retrieved 09/12/2006 from http://en.wikipedia.org/wiki/OSI_Model IP Structure (n.d.). IP Packet Structure. Retrieved 03/04/07 from http://www.freesoft.org/CIE/Course/Section3/7.htm