Transcript UDP

ITP 457
Network Security
Networking Technologies II
UDP
Overview
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UDP
IP
NAT
UDP
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UDP – User Datagram Protocol
Also member of TCP/IP
TCP and UDP are cousins
An application developer can choose to
transmit data using either TCP or UDP
Both protocols cannot be used
simultaneously in an application
UDP Characteristics
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Connectionless – the protocol doesn’t know
or remember the state of a connection
Does not have concept of
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Session initiation
Acknowledgement
No error checking – does not retransmit lost
packets nor does it put them in proper order
UDP
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UDP also called: “Unreliable Damn Protocol”
It is inherently unreliable
Unreliability is ok – IF it can buy you SPEED!
Some applications more interested in getting
packets across the network and don’t need
super high reliability.
Good protocol for a large number of
connections
UDP
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Services that use UDP are
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Streaming Video/ Audio
DNS queries
Online Games
Voice-over-IP (VoIP)
DHCP
DNS
SNMP
RIP
UDP header
UDP source port
UDP destination port
Message Length
Checksum
Data
UDP Ports
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UDP – 65,535 ports
Some typical ports:
 53 – DNS (Domain Name Server)
 67 – DHCP (Dynamic Host Control Protocol)
 69 – TFTP (Trivial File Transfer Protocol)
 161 – SNMP (Simple Network Management Protocol)
 514 – Syslog
 6112 – Battle.NET
 14567 – Battlefield 1492
 26000 – Quake Server
 27015 – Halflife Server
For a searchable database of known ports:
 http://www.ports-services.com/
IS UDP less secure than TCP?
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YES!
Absence of three-way handshake implies no
Sequence numbers or no control bits.
Difficult for firewalls and routers to track
where the ends systems are in their
communications
We cannot completely turn off UDP, due to
some of the necessary protocols that use
UDP
Port Scanning Lab!!!