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Re: 20000908: LDM port 388

>To: <address@hidden>
>From: "Dan Vietor" <address@hidden>
>Subject: LDM port 388
>Organization: UCAR/Unidata
>Keywords: 200009082028.e88KSNN04012

Hi Dan,
   
You asked:

> I've been asked if the LDM uses both TCP and UDP ports 388?  I was
> assuming it only used TCP ports but I noticed UDP and TCP ports were
> reserved in the /etc/services file.

As far as I can tell, the only use of UDP port 388 is to provide
support for old LDM version 4 protocol.  There is still some use of
LDM 4 protocols at sites receiving WSI radar data via a satellite
feed:  the host that redistributes the WSI data to a local server uses
LDM 4 protocols.

Here's an answer Glenn gave to this some time ago:

  The ldm version 4 protocol requires UDP for the FEEDME and NOTIFYME.
  The ldm version 5 protocol currently uses only TCP. BUT, when we
  drop support for version 4, we are going to try using UDP for
  transport.  We have some experiments and development planned using
  broadcast and multicast which will depend on udp. (The rational is
  that we are network limited, rather than CPU limited. TCP puts more
  load on the network (and the kernel) and less on the user
  process. By moving the product assembly up into user space, and
  using smallish (No network reassembly) UDP packets, we may get
  better performance.)

Whether we will use UDP in this way in the future is unclear, since
our multicast developments are still on hold.

--Russ