Transcript TCP/IP and the DoD Model

CCNA: Cisco Certified
Network Associate Study
Guide
CHAPTER 2:
Internet Protocols
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The CCNA exam topics covered in this
chapter include the following:
Technology
•Evaluate TCP/IP communication processes and
its associated protocols
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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
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TCP/IP and the DoD Model
The TCP/IP Protocol Suite
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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
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(Bootstrap Protocol)
TCP/IP and the DoD Model
Host-to-Host Layer Protocols
Transmission Control Protocol (TCP) Header
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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
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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
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TCP/IP and the DoD Model
Host-to-Host Layer Protocols
User Datagram Protocol (UDP) Header
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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
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TCP/IP and the DoD Model
Key Concepts of Host-to-Host Protocols
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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
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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
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TCP/IP and the DoD Model
Internet Layer Protocols
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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
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TCP/IP and the DoD Model
Internet Layer Protocols
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TCP/IP and the DoD Model
Local APR Broadcast
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TCP/IP and the DoD Model
RARP Broadcast
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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…
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IP Addressing
• Hierarchical Addressing Framework
• Network.node addressing, 32 bits (4bytes)
• The Hierarchical advantage is
increased ability of addresses
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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.
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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?
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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
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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
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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.
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IP Addressing
Summary of the Three Classes of
Networks
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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
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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
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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
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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
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Broadcast Addresses
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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
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