Michael Schloh von Bennewitzmichael@schloh.com18. Juni 2002

INTERNET PROTOCOLSAn overview of ten most common Internet protocols, and how to troubleshoot them

An overview of the ten most common Internet protocols

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What Is a Protocol?

A standard procedure for regulating data transmission between computers.

Allows communication between network nodes.

An overview of the ten most common Internet protocols

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Common Attributes

Standard port num Connection(less) Header structure Text, binary data Encrypted data Useful tools

Generic telnet Generic tcpdump Specific OpenPKG

Complete Frame

HTTP data

TCP header/data

IP header/data

Ethernet header/data

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An overview of the ten most common Internet protocols

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General OSI Layout

7 Application

HTTP TLS SMTPNNTP

FTPLDAP

NTPTFTP

DHCP DNS

6 Presentation

5 Session

4 Transport TCP UDP

3 Network IP

2 Data LinkHardware

1 Physical

also

An overview of the ten most common Internet protocols

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FTP File Transfer Protocol

Ports 21 and 20 Control on port 21 Data on port 20

TCP stream based Text data Unencrypted telnet host 21

An overview of the ten most common Internet protocols

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HTTP Hypertext Transfer Protocol

Port 80 TCP stream Text data Unencrypted telnet host 80

OSSP is an acronym for:Onion Soup & Sweet Potato

An overview of the ten most common Internet protocols

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NNTP Network News Transfer Protocol

Port 119 TCP stream Text data Unencrypted telnet host 119

An overview of the ten most common Internet protocols

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LDAP Lightweight Directory Access Protocol

Port 389 TCP stream Binary data Unencrypted ldapsearch host

LDAP Message Fields

controls

messageID

protocolOp

controlType

criticality

controlValueYou can pick your friends,and you can pick your nose.But you can‘t pick yourfriends‘ noses.

An overview of the ten most common Internet protocols

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SMTP Simple Mail Transfer Protocol

Port 25 TCP stream Text data Unencrypted telnet host 25

An overview of the ten most common Internet protocols

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TLS Transport Layer Security

Port 56 TCP stream Binary data Encrypted openssl host

If I can surf the Internetwith my keyboard, thenwhy can‘t I download thebeach with my surfboard?

An overview of the ten most common Internet protocols

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DHCP Dynamic Host Configuration Protocol

Ports 67 and 68 UDP datagram Binary data Unencrypted dhcping -c client \

-s server -h mac

DHCP Packet Fields

bpOpcode bpHtype

bpGiaddrbpCiaddr bpYiaddr bpSiaddr

bpHlen bpHops

bpXid

bpSecs bpFlags

bpChaddr[] bpSname[]

bpFile[] bpOptions[]

An overview of the ten most common Internet protocols

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Example DHCP Session

An overview of the ten most common Internet protocols

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DNS Domain Name System

Port 53 UDP datagram Binary data Unencrypted host dnszone dnstrace dnszone lamers dnszone

PESP is an acronym for:Pickled Eggs & Salted Peanuts

DNS Message Fields

Header

Question

Answer, Authority, Additional

NAME

CLASS

RDLENGTH

...

ID ...

RCODE

QNAME ...

An overview of the ten most common Internet protocols

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NTP Network Time Protocol

Port 123 UDP datagram Binary data Unencrypted ntpdate -q host

NTP Packet Fields

Type Precision

Leap Indicator Status

Reference Clock Id Reference Timestmp

Estimated Error Estimated Drift Rate

Transmit Timestmp

Originate TimestmpReceive Timestmp

An overview of the ten most common Internet protocols

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TFTP Trivial File Transfer Protocol

Port 69 UDP datagram Binary data Unencrypted tftp

TFTP Packet types

RRQ

DATA

ACK

ERROR

Opcode Block no

Block no

Opcode Errorcode

ErrMsg 0

Opcode Block no

Block no

Block no

Opcode Filename

Mode 00

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An overview of the ten most common Internet protocols

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IETF RFC References

FTP (RFC 959) HTTP (RFC 1945) NNTP (RFC 977) LDAP (RFC 1777) SMTP (RFC 2821) TLS (RFC 2246)

DHCP (RFC 2131) DNS (RFC 1101) NTP (RFC 958) TFTP (RFC 1350)

Not all protocols have RFCs, and some like SSHhave Internet drafts or other documentation.

An overview of the ten most common Internet protocols

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Fin