Download Overview of Computer Networks

CPET 355
5. The Network Layer
Paul I-Hai Lin, Professor
Electrical and Computer Engineering Technology
Purdue University, Fort Wayne Campus
April 5, 2004
Prof. Paul Lin
1
Network Layer - an Overview
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Getting data packets from the source
all the way to the destination
Dealing with end-to-end transmission
Need to know
• Topology of the communication subnet
(routers)
• Chose paths (routing algorithms)
April 5, 2004
Prof. Paul Lin
2
Network Layer
Topics of Discussion
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Network Layer Design Issue
• Services to the TCP Layer
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Connectionless Services (Datagram)
Connection-Oriented Services (Virtual Circuit)
• Subnets
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Routing Algorithms (skipped)
Static Routing (skipped)
Quality of Service
Internetworking
The Network Layer in the Internet
April 5, 2004
Prof. Paul Lin
3
Comparison of Virtual Circuit and
Datagram Subnets
From Fig. 5-4, Page 349, Computer Networks, 4th edition,
Andrew S. Tanenbaum, Prentice Hall
April 5, 2004
Prof. Paul Lin
4
Quality of Service
Requirements
From Fig. 5-30, Page 397, Computer Networks, 4th edition,
Andrew S. Tanenbaum, Prentice Hall
April 5, 2004
Prof. Paul Lin
5
Internetworking
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How Networks Differ
How Networks Can Be Connected
Concatenated Virtual Circuits
Connectionless Internetworking
Tunneling
Internetwork Routing
Fragmentation
April 5, 2004
Prof. Paul Lin
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Connecting Networks
From Fig. 5-42, Page 419, Computer Networks, 4th edition,
Andrew S. Tanenbaum, Prentice Hall
April 5, 2004
Prof. Paul Lin
7
How Networks Differ
From Fig. 5-42, Page 419, Computer Networks, 4th edition,
Andrew S. Tanenbaum, Prentice Hall
April 5, 2004
Prof. Paul Lin
8
How Networks Can be Connected
From Fig. 5-44, Page 421, Computer Networks, 4th edition,
Andrew S. Tanenbaum, Prentice Hall
April 5, 2004
Prof. Paul Lin
9
Collection of Subnetworks
The Internet – a collection of subnets
From Fig. 5-52, Page 433, Computer Networks, 4th edition,
Andrew S. Tanenbaum, Prentice Hall
April 5, 2004
Prof. Paul Lin
10
The IP Protocol
The IPv4 Internet Protocol Header
From Fig. 5-53, Page 434, Computer Networks, 4th edition,
Andrew S. Tanenbaum, Prentice Hall
April 5, 2004
Prof. Paul Lin
11
The IPv4 Datagram
Header + Text Part
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Header Format (20-byte fixed)
• Version (4-bit)
• IHL (4-bit) – how long the header is (in 32-bit
word)
• Type of services (6-bit) - delay, throughput,
reliability)
• Total length (16-bit) - max 65,535 bytes
• Identification (16-bit) – for fragmented data as
tags
• DF (1-bit) – Don’t Fragment
• MF (1-bit) – More Fragment
April 5, 2004
Prof. Paul Lin
12
The IPv4 Datagram
Header + Text Part (continue)
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Header Format (20-byte fixed)
• Fragment Offset (13-bit) – max 8192 data
fragments per datagram
• Time to Live (8-bit) – max 255 second
• Protocol (8-bit) - TCP, UDP, etc; see
www.iana.org
• Header Checksum (16-bit) – detecting errors
• Source Address (32-bit)
• Destination Address (32-bit)
• Options ( 0 or more words, variable length) –
consider future protocols for extensibility
April 5, 2004
Prof. Paul Lin
13
Some of the IP Options
From Fig. 5-54, Page 436, Computer Networks, 4th edition,
Andrew S. Tanenbaum, Prentice Hall
April 5, 2004
Prof. Paul Lin
14
IP Address Formats
From Fig. 5-55, Page 437, Computer Networks, 4th edition,
Andrew S. Tanenbaum, Prentice Hall
April 5, 2004
Prof. Paul Lin
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Network Classes
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Class A – 128 Networks, 16 Million
hosts
Class B – 16,384 Networks, up to
64K hosts
Class C – 2 Million Networks, up to
256 hosts
Class D – Multicast Address
Class E - Reserved
April 5, 2004
Prof. Paul Lin
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Special IP Addresses
From Fig. 5-56, Page 438, Computer Networks, 4th edition,
Andrew S. Tanenbaum, Prentice Hall
April 5, 2004
Prof. Paul Lin
17
Subnets
The Parts of the Network
From Fig. 5-57, Page 439, Computer Networks, 4th edition,
Andrew S. Tanenbaum, Prentice Hall
April 5, 2004
Prof. Paul Lin
18
Subnet Masks
From Fig. 5-58, Page 440, Computer Networks, 4th edition,
Andrew S. Tanenbaum, Prentice Hall
April 5, 2004
Prof. Paul Lin
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