sábado, 27 de junho de 2009

๑ What is the purpose of the port # 5002 ?

Ports are like bridges between the physical network and applications/services on the computer. It's a way for the computer to know what type of data is destined to what service. TCP/IP packets contain information for what port that information is sent. There are several of well known ports out there. The Well Known Ports are those from 0 through 1023. For a list of well known and not well known ports and it's associations check here

As you can see this 5002 port is not even in that wikipedia page so it is definitely a not well known port.

Information about this port and it's purpose is almost unvailable, so i tought i would write something about it as best as i can. The port 5002 is associated with the RFE service, so this is where this discussion will lean.

What's the purpose of the RFE service or what's the RFE for?

RFE stands for Radio Free Ethernet and it was projected on early 90's. It's based on a UDP port meaning that the it isn't connection oriented ( errors have to be managed on the application side ) Here's a quick def:

"Radio Free Ethernet (RFE) is a network audio broadcasting system. It consists of programs and tools that allow packets of audio data to be transmitted around a network. The system is best understood by using the analogy of traditional radio broadcasting"


NETWORK IMPLEMENTATION

Radio Free Ethernet can be configured to broadcast data either in UDP Broadcast packets or using IP Multicasting. These techniques differ in subtle but important ways.

UDP Broadcast packets are broadcast only within the local subnetwork. Network gateway routers do not forward these packets to other networks. When a UDP Broadcast packet is issued, every machine on the subnet receives the packet and discards it, unless a program is specifically registered to listen for that particular packet type. Though the overhead of processing such packets is small, it is normally considered unfriendly to issue many UDP Broadcast packets on a network (RFE normally broadcasts approximately eight packets per second, each containing around 1000 bytes). UDP Broadcast is available for the time being only because older versions of the operating system do not support IP Multicast.

IP Multicasting is an improvement over broadcast techniques. By sending network packets to a particular well-known multicast address, only machines that have registered interest in that address will receive the data (packet filtering is usually performed in the network interface hardware). Some experimental IP routers exist that will forward multicast packets to other networks. Such forwarding is only performed when there is a listener on the destination network, and when the packet itself is identified as forwardable.

In order for Radio Free Ethernet to function properly, the following entry should be present in the NIS hosts map:


RadioFreeEthernet 224.0.3.255 # IP Multicast address


For more information check this hard to find link:

http://docs.sun.com/app/docs/doc/805-3178/6j31hi8kq?a=view

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