April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 11

CPET 355 CPET 355

5. The Network Layer5. The Network Layer

Paul I-Hai Lin, Professor Paul I-Hai Lin, Professor Electrical and Computer Engineering TechnologyElectrical and Computer Engineering Technology

Purdue University, Fort Wayne CampusPurdue University, Fort Wayne Campus

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 22

Network Layer - an OverviewNetwork Layer - an Overview

Getting data packets from the source Getting data packets from the source all the way to the destinationall the way to the destination

Dealing with end-to-end transmissionDealing with end-to-end transmission Need to knowNeed to know

• Topology of the communication subnet Topology of the communication subnet (routers)(routers)

• Chose paths (routing algorithms)Chose paths (routing algorithms)

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 33

Network LayerNetwork LayerTopics of DiscussionTopics of Discussion

Network Layer Design IssueNetwork 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 ServiceQuality of Service Internetworking Internetworking The Network Layer in the InternetThe Network Layer in the Internet

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 44

Comparison of Virtual Circuit and Comparison of Virtual Circuit and Datagram SubnetsDatagram Subnets

From Fig. 5-4, Page 349, Computer Networks, 4th edition, Andrew S. Tanenbaum, Prentice Hall

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 55

Quality of ServiceQuality of ServiceRequirementsRequirements

From Fig. 5-30, Page 397, Computer Networks, 4th edition, Andrew S. Tanenbaum, Prentice Hall

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 66

InternetworkingInternetworking

• How Networks DifferHow Networks Differ• How Networks Can Be ConnectedHow Networks Can Be Connected• Concatenated Virtual CircuitsConcatenated Virtual Circuits• Connectionless InternetworkingConnectionless Internetworking• TunnelingTunneling• Internetwork RoutingInternetwork Routing• FragmentationFragmentation

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 77

Connecting NetworksConnecting Networks

From Fig. 5-42, Page 419, Computer Networks, 4th edition, Andrew S. Tanenbaum, Prentice Hall

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 88

How Networks DifferHow Networks Differ

From Fig. 5-42, Page 419, Computer Networks, 4th edition, Andrew S. Tanenbaum, Prentice Hall

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 99

How Networks Can be ConnectedHow Networks Can be Connected

From Fig. 5-44, Page 421, Computer Networks, 4th edition, Andrew S. Tanenbaum, Prentice Hall

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 1010

Collection of SubnetworksCollection of SubnetworksThe Internet – a collection of subnetsThe Internet – a collection of subnets

From Fig. 5-52, Page 433, Computer Networks, 4th edition, Andrew S. Tanenbaum, Prentice Hall

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 1111

The IP ProtocolThe IP ProtocolThe IPv4 Internet Protocol HeaderThe IPv4 Internet Protocol Header

From Fig. 5-53, Page 434, Computer Networks, 4th edition, Andrew S. Tanenbaum, Prentice Hall

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 1212

The IPv4 DatagramThe IPv4 DatagramHeader + Text PartHeader + 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 IHL (4-bit) – how long the header is (in 32-bit

word)word)• Type of services (6-bit) - delay, throughput, Type of services (6-bit) - delay, throughput,

reliability)reliability)• Total length (16-bit) - max 65,535 bytesTotal length (16-bit) - max 65,535 bytes• Identification (16-bit) – for fragmented data as Identification (16-bit) – for fragmented data as

tagstags• DF (1-bit) – Don’t FragmentDF (1-bit) – Don’t Fragment• MF (1-bit) – More FragmentMF (1-bit) – More Fragment

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 1313

The IPv4 DatagramThe IPv4 DatagramHeader + Text Part (continue)Header + Text Part (continue)

Header Format (20-byte fixed)Header Format (20-byte fixed)• Fragment Offset (13-bit) – max 8192 data Fragment Offset (13-bit) – max 8192 data

fragments per datagramfragments per datagram• Time to Live (8-bit) – max 255 secondTime to Live (8-bit) – max 255 second• Protocol (8-bit) - TCP, UDP, etc; see Protocol (8-bit) - TCP, UDP, etc; see

www.iana.orgwww.iana.org• Header Checksum (16-bit) – detecting errors Header 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) – Options ( 0 or more words, variable length) –

consider future protocols for extensibilityconsider future protocols for extensibility

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 1414

Some of the IP OptionsSome of the IP Options

From Fig. 5-54, Page 436, Computer Networks, 4th edition, Andrew S. Tanenbaum, Prentice Hall

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 1515

IP Address FormatsIP Address Formats

From Fig. 5-55, Page 437, Computer Networks, 4th edition, Andrew S. Tanenbaum, Prentice Hall

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 1616

Network ClassesNetwork Classes

Class A – 128 Networks, 16 Million Class A – 128 Networks, 16 Million hostshosts

Class B – 16,384 Networks, up to 64K Class B – 16,384 Networks, up to 64K hostshosts

Class C – 2 Million Networks, up to Class C – 2 Million Networks, up to 256 hosts256 hosts

Class D – Multicast AddressClass D – Multicast Address Class E - ReservedClass E - Reserved

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 1717

Special IP AddressesSpecial IP Addresses

From Fig. 5-56, Page 438, Computer Networks, 4th edition, Andrew S. Tanenbaum, Prentice Hall

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 1818

SubnetsSubnetsThe Parts of the NetworkThe Parts of the Network

From Fig. 5-57, Page 439, Computer Networks, 4th edition, Andrew S. Tanenbaum, Prentice Hall

April 5, 2004April 5, 2004 Prof. Paul LinProf. Paul Lin 1919

Subnet MasksSubnet Masks

From Fig. 5-58, Page 440, Computer Networks, 4th edition, Andrew S. Tanenbaum, Prentice Hall