Subject: Comments on an
Article.
Author: <withheld>
Date: 5/4/99 10:33 AM
Mr. Gillin, I have
enjoyed reading the articles in Computer World and have found them to be good sources of
information. Though not deeply technical, they often contain insight that is useful to me
in attempting to understand what is coming next by providing good information on corporate
mergers and new product offerings.
The page at the link
below contains an article on the impact of the Year 2000 date change on older local area
network (LAN) and wide area network (WAN) equipment. I am bringing this to your attention
because the information in the article is wildly misleading.
http://www.computerworld.com/home/print.nsf/CWFlash/990503gear
The basic premise is that
routers, switches, and hubs will stop passing traffic if they are unable to determine the
proper date or the date is substantially inaccurate. I've provided a brief description of
how these devices function in an effort to show why these devices are not functionally
impacted by the date. The exceptions for when time and date may impact the function of
some of these devices are listed after the descriptions. The three types of devices are
Hubs, Switches, and Routers.
Hub - A is hub multi-port
LAN device that transmits all packets (a unit of network traffic) it receives in one port
out all of the other ports. At no time does the time or date play a role in its operation.
Managed hubs use the date and time to log events. Since this is a monitoring only
function, an incorrect date would only cause the log to report the incorrect date in the
log. This will have no impact on the operation of LAN traffic.
Switch - A switch is like
a hub except that it learns which ports other network devices reside on. When it receives
a packet and does not know which port the destination network address resides on, it sends
it out all of its ports. If it knows which port the destination address resides on, it
sends the packet out that port only. Again no attention is paid to the time or date.
Nearly all switches are managed and are subject to incorrect dates in the logs and this
will have no impact on the operation of LAN traffic.
Routers - Routers are
devices that connect LANs and WANS to each other. While hubs and switches are usually only
concerned with the address assigned to the networking hardware, routers decide which port
to send packets out based on a higher level address, like the TCP/IP or IPX address. As
with hubs and switches, the time and date do not play a role in the forwarding of packets.
All routers are managed devices and use the time and date in logging events.
There are exceptions to
the idea that network devices will not be impacted by the year 2000 date change problem.
The two most clear are when the network device is used as a time source and when a remote
access device is set to not allow connections at certain times or days.
NTP stands for Network
Time Protocol. Its purpose is to allow access to a trusted time source. If a network
router is used to collect the current time and date and is unable to correctly deal with
the date it receives, then it is likely to pass on the wrong date. Since the date is
typically passed on to servers and then to workstations, this can cause the systems that
are year 2000 compliant to have a wrong date. The solution is to correct the problem with
the router (or perhaps switch) or use another device to provide your link to the trusted
time source.
Many companies limit
remote access to the company's network to certain times of certain days of the week. If
the date is wrong, then the day of the week is likely to be wrong also. This will make for
unpredictable remote access for dial in users. Most companies use a server-based solution
for authentication to remote access users. In these cases, the date and time of the server
is used and the router's date and time are not relevant. There are cases where the router
provides all of the authentication and in these cases, there is likely to be a problem.
