RE: CreateIpForwardEntry for multicast on Server 2003

From: Steven Schrier (anonymous_at_discussions.microsoft.com)
Date: 04/30/04

  • Next message: Sam Hobbs: "Re: Detecting which networking interface received a UDP multicast packet." 
    Date: Fri, 30 Apr 2004 13:16:06 -0700

    Rhett,

     Thanks for getting back to me.

     I can give a little background. Our company manufactures military type two-way radios that have data transmission capabilities. As a part of the process of extending IP networks over these radios we use an NDIS driver to build the Windows IP stack, and the NT Service component to transfer data between the driver and another socket based application that controls the radio equipment. The NDIS driver appears to the system as an Ethernet interface. When the network driver starts during boot, the network media is reported to NDIS as being in the "media disconnected" state. After the service code has established communications with the driver and the radio control application the driver sets the media state to connected. There could be any period of time between these two events. After the driver state goes to "media connected" the service begin checking the drivers operational state using GetIfEntry(). When the state changes to operational which is a matter of tens of millisecs, the service attempts to populate
     the multicast routing table. The situation I am looking at, is the PC has been running for hours, so any O/S support services should be available. It's the binding of the IP stack components that appears to take upwards of 5 seconds.

     One of our requirements is to allow a standard multicast "chat" applications to communicate between LAN based PCs and RF Networked PCs. As I understand it a multicast router is required to forward the multicast traffic between the RF and LAN networks which are seperate IP subnets. I am also under the impression that only the Server product contains the multicast router / proxy component. If not for this requirement I wouldn't be concerned about this issue with Server 2003.

     I added code to call GetAdaptersInfo(). Just prior to the CreateIpForwardEntry() that fails. The IP_ADAPTER_INFO structure does contain the proper IP Address in the IpAddressList.

     I also noticed some strange (to me) operation when enabling, and disabling the Routing and Remote Access service. When RAS is enabled I have set IGMP Proxy for the LAN subnet, and IGMP Router for the RF subnet.

     When RAS is enabled a call to CreateIpForwardEntry() for a unicast address appears to always return success. However in some cases the route does not appear when the "route print" command is issued. Also any packets to that destination are not routed.

     When RAS is enabled a call to CreateIpForwardEntry() for a multicast address appears to always fail no matter how long I wait. It also fails when the same function is attempted using the "route add" command.

     When RAS is disabled (service stopped) CreateIpForwardEntry() for either unicast or multicast will fail if attempted too soon. The same operation will also fail using the "route add" command if attempted too soon.

     Is the failure in setting multicast routes with RAS running (which I need) a normal server thing ?

     Thanks for the support.

       Steve Schrier

  • Next message: Sam Hobbs: "Re: Detecting which networking interface received a UDP multicast packet."

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