qspiders - upper layer-protocols

UPPER LAYER UPPER LAYER PROTOCOLSPROTOCOLS

What Is TCP/IP?What Is TCP/IP?• A suite of protocols• Rules that dictate how packets of information are sent across multiple networks

• Addressing• Error checking

TCP/IP ProtocolTCP/IP Protocol• The Transmission Control Protocol/Internet

Protocol (TCP/IP) suit was created by the Department of Defense (DoD).

• The Internet Protocol can be used to communicate across any set of interconnected networks.

• TCP/IP supports both LAN and WAN communications.

• IP suite includes not only Layer 3 and 4 specifications but also specifications for common applications like e-mail, remote login, terminal emulation and file transfer.

• The TCP/IP protocol stack maps closely to the OSI model in the lower layers.

The DoD & OSIThe DoD & OSI

Application

Application

PresentationSession

TransportNetwork

Data Link

Physical

Host-to-HostInternet

Network Access

DoD Model OSI Model

TCP/IP Protocol Suit TCP/IP Protocol Suit atat DoD DoDDoD Model

Process /Application

Host-to-Host

Internet

Network Access

TCP/IP Protocol Suit

Telnet FTP LPD SNMP

X WindowNFSSMTPTFTP

TCP UDP

ICMP

Ethernet

ARP RARP

IP

FastEthernet

TokenRing FDDI

BootP

TCP/IP ApplicationsTCP/IP Applications• Application layer

• File Transfer Protocol (FTP)• Remote Login (Telnet)• E-mail (SMTP)

• Transport layer• Transport Control Protocol (TCP)• User Datagram Protocol (UDP)

• Network layer• Internet Protocol (IP)

• Data link & physical layer• LAN Ethernet, Token Ring, FDDI, etc.• WAN Serial lines, Frame Relay, X.25, etc.

Internet Layer Internet Layer OverviewOverview

• In the OSI reference model, the network layer corresponds to the TCP/IP Internet layer.

Internet Protocol (IP)

Internet Control MessageProtocol (ICMP)

Address ResolutionProtocol (ARP)

Reverse AddressResolution Protocol (RARP)

Application

Transport

Internet

Data-Link

Physical

Internet ProtocolInternet Protocol• Provides connectionless, best - effort delivery routing of datagrams.

• IP is not concerned with the content of the datagrams.

• It looks for a way to move the datagrams to their destination.

IP DatagramIP DatagramVersion

(4)

Destination IP Address (32)

Options (0 or 32 if Any)

Data (Varies if Any)

1Bit 0 Bit 15 Bit 16 Bit 31Header

Length (4)Type

of Service (8) Total Length (16)

Identification (16)Flags

(3) Fragment Offset (13)

Time-to-Live (8) Protocol (8) Header Checksum (16)

Source IP Address (32)

20Bytes

IP DatagramIP Datagram• Version – Currently used IP version

• Header Length – Datagram header length

• TOS – Level of importance assigned by a particular upper-layer protocol

• Total Length- Length of packet in bytes including Data and Header

• Identification – Identifies current datagram (Sequence Number)

• Flags – Specifies whether the packet can be fragmented or not

• Fragment Offset – Used to piece together datagram fragments

•TTL – It maintains a counter that gradually decreases, in increments, to zero

• Protocol – It indicates which upper-layer protocol receives incoming packets

• Header Checksum – Calculated checksum of the header to check its integrity

• Source IP Address – Sending node IP Address

• Destination IP Address – Receiving node IP Address

• Options – It allows IP to support various options like security

• Data – Upper layer information (maximum 64Kb)

•Determines destination upper-layer protocol

Protocol FieldProtocol Field

TransportLayer

InternetLayer

TCP UDP

ProtocolNumbers

IP

176

Address Resolution Protocol Address Resolution Protocol (ARP)(ARP)

• ARP works at Internet Layer of DoD Model• It is used to resolve MAC address with the help of a known IP address.

• All resolved MAC addresses are maintained in ARP cache table is maintained.

• To send a datagram this ARP cache table is checked and if not found then a broadcast is sent along with the IP address.

• Machine with that IP address responds and the MAC address is cached.

Address Resolution Address Resolution ProtocolProtocol

172.16.3.1 172.16.3.2

IP: 172.16.3.2 = ???

I need the Ethernet address of 176.16.3.2.


172.16.3.1 172.16.3.2

IP: 172.16.3.2 = ???

I heard that broadcast. The message is for me. Here is my Ethernet address.



172.16.3.1

IP: 172.16.3.2 Ethernet: 0800.0020.1111

172.16.3.2

IP: 172.16.3.2 = ???




Map IP Ethernet

172.16.3.1

IP: 172.16.3.2 Ethernet: 0800.0020.1111

172.16.3.2

IP: 172.16.3.2 = ???



RARP (Reverse ARP)RARP (Reverse ARP)• This also works at Internet Layer. • It works exactly opposite of ARP• It resolves an IP address with the

help of a known MAC addres.• DHCP is the example of an RARP

implementation.• Workstations get their IP address

from a RARP server or DHCP server with the help of RARP.

Reverse ARPReverse ARP

Ethernet: 0800.0020.1111 IP = ???

What is my IP address?


Ethernet: 0800.0020.1111 IP = ???


I heard that broadcast. Your IP address is 172.16.3.25.


Ethernet: 0800.0020.1111IP: 172.16.3.25

Ethernet: 0800.0020.1111 IP = ???




•Map Ethernet IP

Ethernet: 0800.0020.1111IP: 172.16.3.25

Ethernet: 0800.0020.1111 IP = ???



Bootstrap Protocol Bootstrap Protocol (BootP)(BootP)

• BootP stands for BootStrap Protocol.• BootP is used by a diskless machine to learn the following:

• Its own IP address• The IP address and host name of a server machine.

• The boot filename of a file that is to be loaded into memory and executed at boot-up.

• BootP is an old program and is now called the DHCP.

DHCP (Dynamic Host DHCP (Dynamic Host Configuration Protocol)Configuration Protocol)

• The DHCP server dynamically assigns IP address to hosts.

• All types of Hardware can be used as a DHCP server, even a Cisco Router.

• BootP can also send an operating system that a host can boot from. DHCP can not perform this function.

• Following information is provided by DHCP while host registers for an IP address:

• IP Address• Subnet mask• Domain name• Default gateway (router)• DNS

Internet Control Internet Control Message Message ProtocolProtocol

Application

Transport

Internet

Data-Link

Physical

Destination Unreachable

Echo (Ping)

Other

ICMP1

•ICMP messages are carried in IP datagrams and used to send error and control messages.

ICMP PingICMP Ping

Transport Layer Transport Layer OverviewOverview

Transmission ControlProtocol (TCP)

User Datagram Protocol (UDP)

Application

Transport

Internet

Data-Link

Physical

Connection-Oriented

Connectionless

Transmission Control Protocol Transmission Control Protocol (TCP)(TCP)

• TCP works at Transport Layer

• TCP is a connection oriented protocol.

• TCP is responsible for breaking messages into segments and reassembling them.

• Supplies a virtual circuit between end-user application.

TCP Segment FormatTCP Segment Format

Source Port (16) Destination Port (16)

Sequence Number (32)

HeaderLength (4)

Acknowledgment Number (32)

Reserved (6) Code Bits (6) Window (16)

Checksum (16) Urgent (16)

Options (0 or 32 if Any)

Data (Varies)

20Bytes

Bit 0 Bit 15 Bit 16 Bit 31

TCP Segment FormatTCP Segment Format• Source port – Number of the calling port

• Destination Port – Number of the called port

• Sequence Number – Number used to ensure correct sequencing of the arriving data

• Acknowledgement Number – Next expected TCP octet

• Header Length – Length of the TCP header

• Reserved – Set to zero

• Code Bits – Control Functions (setup and termination of a session)

• Window – Number of octets that the sender is willing to accept

• Checksum – Calculated checksum of the header and data fields

• Urgent Pointer – Indication of the end of the urgent data

• Options – One option currently defined (maximum TCP segment size)

• Data – Upper layer protocol data

Port NumbersPort Numbers

TCP

Port Numbers

FTP

TransportLayer

TELNET

DNS

SNMP

TFTP

SMTP

UDP

ApplicationLayer

21 23 25 53 69 161

RIP

520

TCP Port NumbersTCP Port NumbersSource

PortDestination

Port …

Host A

1028 23 …SP DP

Host ZTelnet Z

Destination port = 23.Send packet to my

Telnet application.

Send SYN (seq = 100 ctl = SYN)

SYN Received

Send SYN, ACK (seq = 300 ack = 101 ctl = syn,ack)

Established(seq = 101 ack = 301 ctl = ack)

Host A Host B

1

2

3

SYN Received

TCP Three-Way TCP Three-Way Handshake/Open ConnectionHandshake/Open Connection

• Window Size = 1

Sender Receiver

Send 1 Receive 1

Receive ACK 2 Send ACK 2

Send 2Receive 2

Receive ACK 3Send ACK 3

Send 3Receive 3

Receive ACK 4 Send ACK 4

TCP Simple TCP Simple AcknowledgmentAcknowledgment

TCP Sequence and TCP Sequence and Acknowledgment Acknowledgment

NumbersNumbersSource

PortDestination

Port …Sequence Acknowledgment

1028 23

Source Dest.

1111

Seq.

2

Ack.

1028 23

Source Dest.

1010

Seq.

1

Ack.

102823

Source Dest.

1111

Seq.

1

Ack.

.

I just got number10, now I need number 11.

I justsent number10

Window Size = 3Send 2

TCP WindowingTCP WindowingSender Window Size = 3

Send 1


ACK 3Window Size = 2

Packet 3 IsDropped



ACK 5Window Size = 2

ReceiverWindow Size = 3

UDP (User Datagram UDP (User Datagram Protocol)Protocol)

• A connectionless and unacknowledged protocol.• UDP is also responsible for transmitting messages.• But no checking for segment delivery is provided. • UDP depends on upper layer protocol for reliability.• TCP and UDP uses Port no. to listen to a particular

services.

• No sequence or acknowledgment fields

UDP Segment UDP Segment FormatFormat

Source Port (16) Destination Port (16)

Length (16)

Data (if Any)

1Bit 0 Bit 15 Bit 16 Bit 31

Checksum (16)

8Bytes

UDP Segment UDP Segment FormatFormat

• Source port – Number of the calling port

• Destination Port – Number of the called port

• Length – Number of bytes, including header and data

• Checksum – Calculated checksum of the header and data fields

• Data – Upper layer protocol data

Application Layer Application Layer OverviewOverview

*Used by the Router

Application

Transport

Internet

Data-Link

Physical

File Transfer- TFTP*- FTP*- NFS

E-Mail- SMTP

Remote Login- Telnet*- rlogin*

Network Management- SNMP*

Name Management- DNS*

TelnetTelnet• Telnet is used for Terminal Emulation. • It allows a user sitting on a remote machine to access the resources of another machine.

• It allows you to transfer files from one machine to another.

• It also allows access to both directories and files.

• It uses TCP for data transfer and hence slow but reliable.

Network File System Network File System (NFS)(NFS)

• It is jewel of protocols specializing in file sharing.• It allows two different types of file systems to interoperate.• This is striped down version of FTP.• It has no directory browsing abilities.• It can only send and receive files.

• It uses UDP for data transfer and hence faster but not reliable.

LPD (Line Printer LPD (Line Printer Daemon)Daemon)

• The Line Printer Protocol is designed for Printer sharing.

• The LPD along with the LPR (Line Printer Program) allows print jobs to spooled and sent to the network’s printers using TCP/IP.

X Window• X-windows defines a protocol for the

writing of graphical user interface-based client/Server application.

Simple Network Simple Network Management ProtocolManagement Protocol• SNMP enable a central management of

Network.• Using SNMP an administrator can watch the

entire network.• SNMP works with TCP/IP.• IT uses UDP for transportation of the data.

DNS (Domain Name DNS (Domain Name Service)Service)

• DNS resolves FQDNs with IP address.• DNS allows you to use a domain name to

specify and IP address.• It maintains a database for IP address and

Hostnames.• On every query it checks this database and

resolves the IP.

– Unique addressing allows communication between end stations.

– Path choice is based on destination address.• Location is represented by an address

Introduction to TCP/IP Introduction to TCP/IP AddressesAddresses

172.18.0.2

172.18.0.1

172.17.0.2172.17.0.1

172.16.0.2

172.16.0.1

SA DAHDR DATA

10.13.0.0 192.168.1.010.13.0.1 192.168.1.1

IPv4 AddressingIPv4 Addressing

• 32-bit addresses• Commonly expressed in dotted

decimal format (e.g., 192.168.10.12)• Each “dotted decimal” is commonly

called an octet (8 bits)

IP AddressingIP Addressing

255 255 255 255

DottedDecimal

Maximum

Network Host

32 bits


255 255 255 255

DottedDecimal

Maximum

Network Host

128 64 32 16 8 4 2 1

11111111 11111111 11111111 11111111Binary

32 bits

1 8 9 16 17 24 25 32

128 64 32 16 8 4 2 1

128 64 32 16 8 4 2 1

128 64 32 16 8 4 2 1


255 255 255 255

DottedDecimal

Maximum

Network Host

128 64 32 16 8 4 2 1

11111111 11111111 11111111 11111111

10101100 00010000 01111010 11001100

Binary

32 bits

172 16 122 204ExampleDecimalExampleBinary

1 8 9 16 17 24 25 32

128 64 32 16 8 4 2 1

128 64 32 16 8 4 2 1

128 64 32 16 8 4 2 1

•Class A:

•Class B:

•Class C:

•Class D: Multicast

•Class E: Research

IP Address ClassesIP Address ClassesNetwork Host Host Host

Network Network Host Host

Network Network Network Host

8 bits 8 bits 8 bits 8 bits

IP Addressing—Class IP Addressing—Class AA

• 10.222.135.17• Network # 10• Host # 222.135.17• Range of class A network IDs: 1–126• Number of available hosts: 16,777,214

IP Addressing—Class IP Addressing—Class BB

• 128.128.141.245• Network # 128.128• Host # 141.245• Range of class B network IDs:

128.1–191.254• Number of available hosts: 65,534

IP Addressing—Class IP Addressing—Class CC

• 192.150.12.1• Network # 192.150.12• Host # 1• Range of class C network IDs:

192.0.1–223.255.254• Number of available hosts: 254

IP Network Address IP Network Address ClassesClasses

0000000001111111

10111111

1111111111011111

00000000 00000000

11111111

11111111 00000000 00000000

00000000

# Networks

126

16,384

2,097,152

# Hosts

254

65,534

16,777,214

Class

ABC

Class A 35.0.0.0

Class B 128.5.0.0

Class C 132.33.33.0 Network Address Space

Host Address Space

Example

IP Address ClassesIP Address Classes1

Class A:Bits:

0NNNNNNN Host Host Host8 9 16 17 24 25 32

Range (1-126)1

Class B:Bits:

10NNNNNN Network Host Host8 9 16 17 24 25 32

Range (128-191)1

Class C:Bits:

110NNNNN Network Network Host

8 9 16 17 24 25 32

Range (192-223)1

Class D:Bits:

1110MMMM Multicast Group Multicast Group Multicast Group

8 9 16 17 2425 32

Range (224-239)

Private Private AddressesAddresses

• Class A – 10.0.0.0 to 10.255.255.255• Class B – 172.16.0.0 to 172.31.255.255• Class C – 192.168.0.0 to 192.168.255.255

11111111

Determining Available Determining Available Host AddressesHost Addresses

172 16 0 0

10101100 00010000 00000000 0000000016 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

Network Host

00000000 00000001

11111111 11111111 11111111 11111110

...... 00000000 00000011

11111101

123

655346553565536-

...

265534

N

2N-2 = 216-2 = 65534

Subnet MaskSubnet Mask

172 16 0 0

255 255 0 0

255 255 255 0

IPAddress

DefaultSubnet

Mask

8-bitSubnet

Mask

Network Host

Network Host

Network Subnet Host

Also written as “/16” where 16 represents the number of 1s in the mask.

Also written as “/24” where 24 represents the number of 1s in the mask.

11111111 11111111 00000000 00000000

Decimal Equivalents of Bit Decimal Equivalents of Bit PatternsPatterns

1 0 0 0 0 0 0 0 = 128

1 1 0 0 0 0 0 0 = 192

1 1 1 0 0 0 0 0 = 224

1 1 1 1 0 0 0 0 = 240

1 1 1 1 1 0 0 0 = 248

1 1 1 1 1 1 0 0 = 252

1 1 1 1 1 1 1 0 = 254

1 1 1 1 1 1 1 1 = 255

128 64 32 16 8 4 2 1

16

Network Host

172 0 0

10101100

11111111

10101100

00010000

11111111

00010000

00000000

00000000

10100000

00000000

00000000

•Subnets not in use—the default

00000010

Subnet Mask without Subnet Mask without SubnetsSubnets

172.16.2.160

255.255.0.0

NetworkNumber

•Network number extended by eight bits

Subnet Mask with Subnet Mask with SubnetsSubnets

16

Network Host

172.16.2.160

255.255.255.0

172 2 0

10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

00000000

00000000

00000010

Subnet

NetworkNumber

128

192

224

240

248

252

254

255

Subnet Mask with Subnets Subnet Mask with Subnets (cont.)(cont.)

Network Host

172.16.2.160

255.255.255.192

10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

11000000

10000000

00000010

Subnet

•Network number extended by ten bits

16172 2 128NetworkNumber

128

192

224

240

248

252

254

255

128

192

224

240

248

252

254

255

Addressing Summary Addressing Summary ExampleExample

16172 2 160

10101100 00010000 1010000000000010 Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

4

1


10101100

11111111

00010000

11111111 11111111

10100000

11000000

00000010 Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

16172 2 160


10101100

11111111

00010000

11111111 11111111

10100000

11000000

00000010 Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

7

16172 2 160


10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010 Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

16172 2 160


10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010

10111111

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

56

16172 2 160


10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010

10111111

10000001

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

56

16172 2 160


10101100

11111111

00010000

11111111 11111111

10100000

11000000

10000000

00000010

10111111

10000001

10111110

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

56

7

16172 2 160


10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

11000000

10000000

00000010

10101100 00010000 00000010 10111111

10101100 00010000 00000010 10000001

10101100 00010000 00000010 10111110

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

1

2

3

4

56

7

8

16172 2 160


10101100

11111111

10101100

00010000

11111111

00010000

11111111

00000010

10100000

11000000

10000000

00000010

10101100 00010000 00000010 10111111

10101100 00010000 00000010 10000001

10101100 00010000 00000010 10111110

Host

Mask

Subnet

Broadcast

Last

First

172.16.2.160

255.255.255.192

172.16.2.128

172.16.2.191

172.16.2.129

172.16.2.190

1

2

3

4

56

7

89

16172 2 160

qspiders - upper layer-protocols

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