1. April 5, 2004 Prof. Paul Lin 1 CPET 355 5. The Network Layer Paul I-Hai Lin, Professor Electrical and Computer Engineering Technology Purdue University, Fort Wayne Campus

2. April 5, 2004 Prof. Paul Lin 2 Network Layer - an Overview Getting data packets from the source all the way to the destination Getting data packets from the source all the way to the destination Dealing with end-to-end transmission Dealing with end-to-end transmission Need to know Need to know Topology of the communication subnet (routers)Topology of the communication subnet (routers) Chose paths (routing algorithms)Chose paths (routing algorithms)

3. April 5, 2004 Prof. Paul Lin 3 Network Layer Topics of Discussion Network Layer Design Issue Network Layer Design Issue Services to the TCP LayerServices to the TCP Layer Connectionless Services (Datagram) Connectionless Services (Datagram) Connection-Oriented Services (Virtual Circuit) Connection-Oriented Services (Virtual Circuit) SubnetsSubnets Routing Algorithms (skipped) Routing Algorithms (skipped) Static Routing (skipped) Static Routing (skipped) Quality of Service Quality of Service Internetworking Internetworking The Network Layer in the Internet The Network Layer in the Internet

4. April 5, 2004 Prof. Paul Lin 4 Comparison of Virtual Circuit and Datagram Subnets From Fig. 5-4, Page 349, Computer Networks, 4 th edition, Andrew S. Tanenbaum, Prentice Hall

5. April 5, 2004 Prof. Paul Lin 5 Quality of Service Requirements From Fig. 5-30, Page 397, Computer Networks, 4 th edition, Andrew S. Tanenbaum, Prentice Hall

6. April 5, 2004 Prof. Paul Lin 6 Internetworking How Networks Differ How Networks Differ How Networks Can Be Connected How Networks Can Be Connected Concatenated Virtual Circuits Concatenated Virtual Circuits Connectionless Internetworking Connectionless Internetworking Tunneling Tunneling Internetwork Routing Internetwork Routing Fragmentation Fragmentation

7. April 5, 2004 Prof. Paul Lin 7 Connecting Networks From Fig. 5-42, Page 419, Computer Networks, 4 th edition, Andrew S. Tanenbaum, Prentice Hall

8. April 5, 2004 Prof. Paul Lin 8 How Networks Differ From Fig. 5-42, Page 419, Computer Networks, 4 th edition, Andrew S. Tanenbaum, Prentice Hall

9. April 5, 2004 Prof. Paul Lin 9 How Networks Can be Connected From Fig. 5-44, Page 421, Computer Networks, 4 th edition, Andrew S. Tanenbaum, Prentice Hall

10. April 5, 2004 Prof. Paul Lin 10 Collection of Subnetworks The Internet – a collection of subnets From Fig. 5-52, Page 433, Computer Networks, 4 th edition, Andrew S. Tanenbaum, Prentice Hall

11. April 5, 2004 Prof. Paul Lin 11 The IP Protocol The IPv4 Internet Protocol Header From Fig. 5-53, Page 434, Computer Networks, 4 th edition, Andrew S. Tanenbaum, Prentice Hall

12. April 5, 2004 Prof. Paul Lin 12 The IPv4 Datagram Header + Text Part Header Format (20-byte fixed) Header Format (20-byte fixed) Version (4-bit)Version (4-bit) IHL (4-bit) – how long the header is (in 32-bit word)IHL (4-bit) – how long the header is (in 32-bit word) Type of services (6-bit) - delay, throughput, reliability)Type of services (6-bit) - delay, throughput, reliability) Total length (16-bit) - max 65,535 bytesTotal length (16-bit) - max 65,535 bytes Identification (16-bit) – for fragmented data as tagsIdentification (16-bit) – for fragmented data as tags DF (1-bit) – Don’t FragmentDF (1-bit) – Don’t Fragment MF (1-bit) – More FragmentMF (1-bit) – More Fragment

13. April 5, 2004 Prof. Paul Lin 13 The IPv4 Datagram Header + Text Part (continue) Header Format (20-byte fixed) Header Format (20-byte fixed) Fragment Offset (13-bit) – max 8192 data fragments per datagramFragment Offset (13-bit) – max 8192 data fragments per datagram Time to Live (8-bit) – max 255 secondTime to Live (8-bit) – max 255 second Protocol (8-bit) - TCP, UDP, etc; see www.iana.orgProtocol (8-bit) - TCP, UDP, etc; see www.iana.org www.iana.org Header Checksum (16-bit) – detecting errorsHeader Checksum (16-bit) – detecting errors Source Address (32-bit)Source Address (32-bit) Destination Address (32-bit)Destination Address (32-bit) Options ( 0 or more words, variable length) – consider future protocols for extensibilityOptions ( 0 or more words, variable length) – consider future protocols for extensibility

14. April 5, 2004 Prof. Paul Lin 14 Some of the IP Options From Fig. 5-54, Page 436, Computer Networks, 4 th edition, Andrew S. Tanenbaum, Prentice Hall

15. April 5, 2004 Prof. Paul Lin 15 IP Address Formats From Fig. 5-55, Page 437, Computer Networks, 4 th edition, Andrew S. Tanenbaum, Prentice Hall

16. April 5, 2004 Prof. Paul Lin 16 Network Classes Class A – 128 Networks, 16 Million hosts Class A – 128 Networks, 16 Million hosts Class B – 16,384 Networks, up to 64K hosts Class B – 16,384 Networks, up to 64K hosts Class C – 2 Million Networks, up to 256 hosts Class C – 2 Million Networks, up to 256 hosts Class D – Multicast Address Class D – Multicast Address Class E - Reserved Class E - Reserved

17. April 5, 2004 Prof. Paul Lin 17 Special IP Addresses From Fig. 5-56, Page 438, Computer Networks, 4 th edition, Andrew S. Tanenbaum, Prentice Hall

18. April 5, 2004 Prof. Paul Lin 18 Subnets The Parts of the Network From Fig. 5-57, Page 439, Computer Networks, 4 th edition, Andrew S. Tanenbaum, Prentice Hall

19. April 5, 2004 Prof. Paul Lin 19 Subnet Masks From Fig. 5-58, Page 440, Computer Networks, 4 th edition, Andrew S. Tanenbaum, Prentice Hall