Download TCP/IP and the DoD Model

CCNA: Cisco Certified
Network Associate Study
Guide
CHAPTER 2:
Internet Protocols
© Wiley Inc. 2006. All Rights Reserved.
The CCNA exam topics covered in this
chapter include the following:
Technology
•Evaluate TCP/IP communication processes and
its associated protocols
© Wiley Inc. 2006. All Rights Reserved.
TCP/IP and the DoD Model
The DoD model is basically a condensed version of the
OSI model—it’s composed of four, instead of seven,
layers:
Process/Application layer
Host-to-Host layer
Internet layer
Network Access layer
© Wiley Inc. 2006. All Rights Reserved.
TCP/IP and the DoD Model
The TCP/IP Protocol Suite
© Wiley Inc. 2006. All Rights Reserved.
TCP/IP and the DoD Model
Process/Application Layer Protocols
• Telnet
• File Transfer Protocol (FTP)
• Trivial File Transfer Protocol (TFTP)
• Network File System (NFS)
• Simple Mail Transfer Protocol (SMTP)
• Line Printer Daemon (LPD)
• X Window
• Simple Network Management Protocol (SNMP)
• Domain Name Service (DNS)
• Dynamic Host Configuration Protocol (DHCP)/BootP
© Wiley Inc. 2006. All Rights Reserved.
(Bootstrap Protocol)
TCP/IP and the DoD Model
Host-to-Host Layer Protocols
Transmission Control Protocol (TCP) Header
© Wiley Inc. 2006. All Rights Reserved.
Transport Layer Overview
Application
Transmission Control
Protocol (TCP)
ConnectionOriented
User Datagram
Protocol (UDP)
Connectionless
Transport
NNTP(119), HTTP (80), HTTPS (443), Telnet (23), FTP (21), SMTP (25): TCP
TFTP (69), SNMP(161): UDP
DNS (53): both TCP and UDP
© Wiley Inc. 2006. All Rights Reserved.
Transmission Control Protocol
(TCP)
• Connection-oriented services
• Uses virtual circuits (three-way handshake)
• Enables devices to send large quantities of data
using windowing in a connection-oriented manner
• Uses acknowledgements
• Considered reliable
Dest
Port
Source
Ack.
Window Sequence
Port
Number number number
Segment
…
CRC
Data
© Wiley Inc. 2006. All Rights Reserved.
TCP/IP and the DoD Model
Host-to-Host Layer Protocols
User Datagram Protocol (UDP) Header
© Wiley Inc. 2006. All Rights Reserved.
User Datagram Protocol (UDP)
•
•
•
•
Simple connectionless service
No windowing
No sequencing
No acknowledgements, which reduces overhead
traffic
Segment
Dest
Port
Source.
Port
Length
CRC
Data
Note: TCP and UDP both have source and destination port numbers
and a CRC field
© Wiley Inc. 2006. All Rights Reserved.
TCP/IP and the DoD Model
Key Concepts of Host-to-Host Protocols
© Wiley Inc. 2006. All Rights Reserved.
TCP/IP and the DoD Model
Port Numbers
• < 1024: “Well-known port numbers”
– Defined in RFC 3232; linked to specific applications or
protocols
• 1024: Dynamically assigned
– Used by upper layers to communicate between hosts
© Wiley Inc. 2006. All Rights Reserved.
TCP/IP and the DoD Model
Internet Layer Protocols
•
•
•
•
•
Internet Protocol (IP)
Internet Control Message Protocol (ICMP)
Address Resolution Protocol (ARP)
Reverse Address Resolution Protocol (RARP)
Proxy ARP
© Wiley Inc. 2006. All Rights Reserved.
TCP/IP and the DoD Model
Internet Layer Protocols
© Wiley Inc. 2006. All Rights Reserved.
Internet Protocol (IP)
• Provides network addressing and routing
through an internetwork
• Connectionless service
Segment
Packet
Dest
IP
Dest
Port
Source
Port
Source
Protocol
IP
…
…
Data
Segment
© Wiley Inc. 2006. All Rights Reserved.
TCP/IP and the DoD Model
Internet Layer Protocols
© Wiley Inc. 2006. All Rights Reserved.
TCP/IP and the DoD Model
Local APR Broadcast
© Wiley Inc. 2006. All Rights Reserved.
TCP/IP and the DoD Model
RARP Broadcast
© Wiley Inc. 2006. All Rights Reserved.
Proxy ARP
• Allows a router to respond to an ARP
request that is intended for a remote host
How do we send packets out of the local network with multiple default gateways?
But proxy Arp can cause network congestion…
© Wiley Inc. 2006. All Rights Reserved.
IP Addressing
• Hierarchical Addressing Framework
• Network.node addressing, 32 bits (4bytes)
• The Hierarchical advantage is
increased ability of addresses
© Wiley Inc. 2006. All Rights Reserved.
Binary to Decimal
The following table shows the decimal values of each bit location in a
nibble and a byte. Remember, a nibble is 4 bits and a byte is 8 bits.
Nibble values
Byte values
8421
128 64 32 16 8 4 2 1
What all this means is that if a one digit (1) is placed in a value spot,
then the nibble or byte takes on that decimal value, and adds it to any
other value spots that have a one. And if a zero (0) is placed in a bit spot,
then you don’t count that value.
© Wiley Inc. 2006. All Rights Reserved.
Binary to Decimal Review
Converting binary to decimal examples:
128 64 32 16 8 4 2 1: Bit values
0
0
0
1
0
1
0
0
1
0
0
1
0
0
0
0
0
1
0
0
1
0
1
1
0
1
0
0
0
1
0
1
1
0
1
1
0
1
0
1
1
1
0 =0
1 = 15
1 = 85
1 = 131
0 = 22
1 = 255
What is the hex equivalent of each binary number?
© Wiley Inc. 2006. All Rights Reserved.
Binary (Cont.)
Bits
0
1
2
3
4
5
6
7
8
Binary
00000000
10000000
11000000
11100000
11110000
11111000
11111100
11111110
11111111
Decimal
0
128
192
224
240
248
252
254
255
© Wiley Inc. 2006. All Rights Reserved.
IP Addressing
The Hierarchical IP Addressing Scheme
• Dotted-decimal, as in 172.163.30.56
• Binary, as in 10101100.00010000.00011110.00111000
• Hexadecimal, as in AC.10.1E.38
© Wiley Inc. 2006. All Rights Reserved.
IP Addressing
Reserved IP Addresses
Address
Function
Network address of all 0s
Interpreted to mean “this network or segment.”
Network address of all 1s
Interpreted to mean “all networks.”
Network 127.0.0.1
Reserved for loopback tests. Designates the
local node and allows that node to send a test
packet to itself without generating network
traffic.
Node address of all 0s
Interpreted to mean “network address” or any
host on specified network.
Node address of all 1s
Interpreted to mean “all nodes” on the specified
network; for example, 128.2.255.255 means “all
nodes” on network 128.2 (Class B address).
Entire IP address set to all 0s
Used by Cisco routers to designate the default
route. Could also mean “any network.”
Entire IP address set to all 1s (same as
255.255.255.255)
Broadcast to all nodes on the current network;
sometimes called an “all 1s broadcast” or
limited broadcast.
© Wiley Inc. 2006. All Rights Reserved.
IP Addressing
Summary of the Three Classes of
Networks
© Wiley Inc. 2006. All Rights Reserved.
IP Addressing
Class A Addresses
• Structure
– Network.node.node.node
• Class A Valid Host IDs
– 10.0.0.0
All host bits off
– 10.255.255.255 All host bits on
– Valid hosts = 10.0.0.1 - 10.255.255.254
• 0’s & 255s can be valid hosts but all hosts bits cannot all be off or
on at the same time!
• 224-2 = 222
© Wiley Inc. 2006. All Rights Reserved.
IP Addressing
• Structure
Class B Addresses
– Network.Network.node.node
• Class B Valid Host IDs
– 172.16.0.0
All host bits off
– 172.16.255.255
All host bits on
– Valid hosts = 172.16.0.1 - 172.16.255.254
• 0’s & 255s can be valid hosts but all hosts bits cannot all be off or
on at the same time!
• 216-2 = 214
© Wiley Inc. 2006. All Rights Reserved.
IP Addressing
Class C Addresses
• Structure
– Network.Network.Network.node
• Class C Valid Host IDs
– 192.168.100.0
All host bits off
– 192.168.100.255
All host bits on
– Valid hosts = 192.168.100.1 - 192.168.100.254
• 0’s & 255s can be valid hosts but all hosts bits cannot all be off or
on at the same time!
• 28-2 = 26
© Wiley Inc. 2006. All Rights Reserved.
IP Addressing
Private IP Addresses
Address Class
Reserved address space
Class A
10.0.0.0 through 10.255.255.255
Class B
172.16.0.0 through 172.31.255.255
Class C
192.168.0.0 through 192.168.255.255
© Wiley Inc. 2006. All Rights Reserved.
Broadcast Addresses
© Wiley Inc. 2006. All Rights Reserved.
Broadcast Addresses
•Layer 2 Broadcasts—These are sent to all nodes on a Lan
•Broadcasts (layer 3)—These are sent to all notes on the
network
•Unicast—These are sent to a single destination host
•Multicast—These are packets sent from a single source, and
transmitted to many devices on different networks
© Wiley Inc. 2006. All Rights Reserved.