HOW CAN I HAVE MULTIPLE LAN-PROFILES IN A CELL WITH ONE CDS SERVER WHEN THE LAN-PROFILE IS SET UP WITH THE CDS?
ITEM: RTA000038142
QUESTION:
Do I have to use a different LAN profile for each TCP/IP subnet for
DTS to work properly under DCE? My TCP/IP mask is 255.255.255.192.
Does this mean that each subnet is considered a separate lan and there-
fore requires a separate lan profile for that lan? How do you determine
which lan-profile to use if a machine is a gateway between the two
lans and you have to specify the lan-profile when you define the cds
for the cell. What if you have only one cell, one cds server and
multiple lans based on the subnet mask? Since the lan-profile is defined
when I set up the cds, I don't see how I can set up multiple lan-
profiles ( one for each lan).Can you please clarify this for me?
Also, is there any reason I wouldn't make all of my machines a DTS
server since there are so few machines on each subnet?
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A: Here are the answers to your questions:
1. Do different lan profiles need to be used for each subnet?
DCE DTS will still work with only one lan profile, but this could
affect the accuracy of the DTS timeservers. When a DTS local server is
configured, information is placed in the lan-profile.
The DTS clerks and DTS servers will look in the lan-profile for local DTS
servers. A global DTS server is placed in the lan-profile and in the
cell-profile. If there are not enough local time servers in the
lan-profile when a time sync is done, DTS will check the cell-profile
for global DTS servers. If a global time server is in a lan-profile,
it is considered a local time server for those DCE systems that refer to
the same lan-profile. The purpose of lan-profiles is to group DTS servers
on the same network together. Network delays affect the inaccuracy value
associated with DTS time.
2. If each net is a separate LAN, do they need separate lan profiles?
If the LANs are all fast (ethernet, token-ring, or fddi) and the have
small delays between them, then it is not as critical to have
different lan profiles. But, if there are routers spread across the
country connected by slower links (x.25, async), then it is better to
have different lan-profiles. Another case would be the same IP subnet
connected by split bridges that may have slow links. In this case, there
is one subnet, but because of the split-bridge, you would want a
different lan-profile on each side of the bridge.
3. If a system is on multiple networks, which lan-profile?
If a system is on multiple networks, base it on either the more accurate
time server (using an external time provider) or the faster network if
the time servers accuracies are comparable.
4. How are extra lan-profiles defined?
When the initial CDS server is defined, it creates /.:/lan-profile.
Other lan-profiles can be created either when additional CDS servers
are configured or when a DCE client is configured. There is an entry
in the SMIT menu for the lan profile to be used or created if needed.
5. Should all DCE systems be DTS Servers?
This will depend on the number of systems and the network.
If there are few DCE systems on each network, with slow links between
the networks, then this is accurate. DTS by default looks for 3 DTS
servers when a time sync is done. It first looks in the lan profile
for local time servers. If enough are not found there, it then checks the
cell profile for global time servers. If the number of required servers
are not found, then the time sync will not occur. There should be at
3 DTS servers accessible to every DCE system.
On the other hand, if there are hundreds of DCE systems in the network,
you don't want all of the configured as DTS servers. This will generate
unnecessary network traffic.
The AIX DCE Administration Guide (SC23-2475-01) has a very good
description of DTS.
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QUESTION:
In answer #1, you said that if the required number of servers could
not be found in the lan-profile, then the machine would go to the cell-
profile and get info. from global-servers until enough servers had been
contacted to meet the minimum server number requirement. Does this mean
that if I had a network that had 10 local lan servers on it and if the
minimum number of servers required parameter was left at its default of
three, then that machine would never check with a global server or a
machine off of the lan in computing its time synch? Is it safe to say
that the way you keep this lan from drifting as a whole away from the
rest of the cell is to ensure that it has at least one courier server?
If so, then what determines how often that courier is contacted by
machines on the lan when they are synching their time?
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QUESTION:
You also mention in answer #5 that all machines should not be set up
to be dts servers because of the increase in network traffic. How is
this an extra burden since all machines check (clerk or server) check
the lan-profile for other machines to poll. If all of the other machines
were servers, I don't see how this would cause any more traffic than
a clerk polling other clerks and servers. Could you please clarify
this misunderstanding for me. Thanks so much˘
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A: If the minimum number of time servers are defined in the lan
profile and no courier time server is defined, then it is possible
for the time to drift. Having a local time server configured as a
courier time server will guarantee that one global time server is
used when the time servers synchronize. If a global time server is
configured in the same lan-profile it is not considered a global
time server. It is a global time server to local time servers defined
in other lan profiles. The best way to keep time is to connect either
a global or a local time server to an external time provider.
Configuring all systems as time servers as opposed to configuring
the minimum plus a a few spare, will ensure better clock inaccuracy.
If there were 20 DCE systems on a network, with all configured as time
servers, then there are many different combinations of time servers that
can be synchronized. This can make the clock adjustment more erratic
and inaccurate as opposed to having 4-5 time servers on a network.
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QUESTION:
So, do I understand you to mean that we want to minimize the number of
servers to cause the same ones to be used each time and therefore keep
the time relatively accurate? I realize that clerks check with other
clerks and servers but that servers only check with servers. Are you
also suggesting that I keep the number of servers low so that if I have
a courier server, it will always be used in the synchronization? I could
see it being possible that if I had a large number of servers on the
lan, the servers could synchronize each other without checking the
courier server on a regular basis. This could cause the servers as a
whole to drift. Is this correct?
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A: It is best to have 3 time servers available plus one or two
more in case one is declared faulty. When clerks synchronize, they
do not check with other clerks, the only look for the minimum number
of time servers. The clerk then adjusts his clock increment based on the
time servers' clocks. The clerk does not use his own time in calculating
the new time. DTS time servers do use their own time value in addition
to other DTS time servers when syncing time. If there is a courier time
server present on a network, all time syncs (both clerks and servers)
will include a global DTS time server. A courier time server will not
allow time to drift between networks.
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This item was created from library item Q651504 CPCQW
Additional search words:
CDS CELL COMMUNICATIO CPCQW DCE FEB94 IX LAN MULTIPLE OZNEW PROFILE
PROFILES RISCDCE RISCSYSTEM SERVER SET SETTING SOFTWARE UP
WWQA: ITEM: RTA000038142 ITEM: RTA000038142
Dated: 01/1995 Category: RISCDCE
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