LAN Digital Audio
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Transcript of LAN Digital Audio
Greg Van DyneDecember 4, 2007
AgendaIntroductionTechnical OverviewProtocols DemonstrationFuture TrendsReferences
IntroductionPort Forwarding
Opening a port in a router or firewall residing in a private network in order to let a party from the outside world contact a user inside. For example, opening ports for VoIP and videoconferencing traffic makes two-way communications easier no matter which side initiates the call. Also called "port mapping," port forwarding can be done by manual configuration or by software.
*definition courtesy of PCWorld.com
What is a port?represents an endpoint or "channel" for network
communicationsOne computer sends data from port of one IP address
to anotherPort numbers can theoretically range from 0 to 65535Only one application can be used at a time on any
given portWhy forward a port?
With routers, firewalls prevent direct comm. between IPs
Ports
A Few Common Ports21 – FTP22 – Secure Shell (SSH)23 – Telnet80 – HTTP110 – POP3 mail3389 – Remote Desktop Protocol (RDP)6112 – Blizzard’s Battle.net gaming service
(Unofficial)*Unofficial – not registered with IANA (Internet Assigned Numbers Authority)
Some Familiar ConceptsTCP – Transfer Control Protocol - 2 computers
directly connect, and remain connected for duration of session *similar to a telephone call
UDP – User Datagram Protocol – sends data and relies on devices in between to deliver properly. Not as reliable *like putting mail in mailbox
NAT – Network Address Translation – determines destinati0on of packets sent to network. This is where port forwarding comes into play.
Static vs. Dynamic IPStatic
Usually ocnfigured within OSEnsures that internal IP never changesPorts can be forwarded once, and will not
require any changes in the futureDynamic
Internal IP fluctuatesCan cause port forwarding not to work
Port TriggeringDynamic port forwarding
Port triggering allows for port to to open only when a certain application is running
Once application stops, access to that port is turned off
Slightly more secure
Things to considerThe need to forward the packets that come to the
router's forwarded port, and the need to rewrite them so that the private machine sees them as originating from the router
Only one networked machine can use a specific forwarded port at one time
Traditional port forwarding allows the entire world access to the port, thus security is reduced
Ports can be changed within registry if unofficial
Reverse Port ForwardingAlso called reverse tunnelingComposed of session server (SS) and session client
(SC)SS connects with session port, SC connects with
session server componentSS tunes in to port that needs forwardedWhen connection is done, it’s forwarded directly to SC
with an accessible destination to that SCUsually needed when a port is behind a router or
firewall but that router or firewall is not configurable with normal port forwarding for one reason or another
ReferencesCadden, C. (2006) “MP3 Player Market to Reach
286 Million Units by 2010.” In-Stat.com. Retrieved Nov. 23, 2007. http://www.instat.com/press.asp?ID=1648&sku=I
N0603155ID.Snell, J. (2004) “How AirTunes Works”
Macworld.com. Retrieved Nov. 23, 2007. http://www.macworld.com/weblogs/editors/archi
ves/000212.php.Wikipedia. (2007) “Digital Living Network
Alliance.” http://en.wikipedia.org/wiki/Digital_Living_Network _Alliance