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Issue
57 - September 2008
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Non-stop
Internet Service and Network Connectivity
By
C Y Kwok
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This article addresses the measures that the Computing Services Centre
(CSC) plans to take to enhance the network infrastructure such
that the Internet will remain accessible to users when all the
IT services provided from inside the Main Computer Room (MCR)
in the Main Campus become unavailable under such condition as
a major disaster.
The Concept
Currently, almost all the critical IT services (central servers, core networking
equipment, core VoIP equipment, Internet links and routers, fibre
cable plant, etc.) are either wholly or partly housed inside the
MCR. When something disastrous happens such as a major fire outbreak
or a total power blackout, inside the MCR, all the critical IT
services will be wiped out altogether, resulting in no Internet,
no email, no e-learning, no IP phones, no wireless LAN, no file
service, no network printing, etc. for all the users. Therefore,
it is required to set up a Secondary Computer Room (SCR), and
from there providing a non-stop network connectivity for accessing
the critical IT services no matter these services are provided
through the MCR, the SCR or even when they are outsourced. To
enable this non-stop network connectivity, it is required to have
the following setup at the SCR:
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a redundant set of network cables and switches along the connection
paths which are originated from users’ switches and terminated
at switches inside SCR
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the necessary network services such as DNS, Active Directory,
LDAP etc.
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other additional servers and storages and
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Internet link.
It is worth mentioning that, even if most of or all the existing
IT services inside the MCR in future will be outsourced (i.e.,
items listed in (iii) residing at the service provider(s)), the
SCR is still required to house the items listed in (i), (ii) and
(iv) in order to provide the required resiliency.
The Implementation
For years, the University has been running short of spaces in the
Main Campus to meet ongoing demands for new classrooms, staff
offices, research labs, wiring closets, etc. Finding a space in
the Main Campus for a SCR is totally out of the question despite
the fact that there is an urgent need. Without a SCR, there is
no way the CSC can provide non-stop Internet services. As a last
resort, the CSC has chosen the Main Equipment Room in the Student
Residence Phase III to be the SCR.
Single-mode fibre cables (2 x 96 cores) were laid between the student hostels
and the Main Campus at the time when the Student Residence Phase
II was under construction. The fibre cables enable the CSC to
extend the campus network to the student hostels without the need
of leasing expensive data circuits from the local carriers. However,
these fibre cables inside the Main Campus are all terminated in
the Main Computer Room. They will be rendered unusable when the
MCR is gone under a disaster. As a solution for providing users
with an alternative connection path to the Internet and Intranet
by-passing the MCR but through SCR, the following will be carried
out:
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Additional core and distribution switches will
be installed at SCR. The core switch there will be connected
to one of the same in the MCR.
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Additional single-mode fibre cables (2 x 96 cores) will be laid between
the SCR and one of the wiring centres on the 5/F of the Academic
Building (a number of communication closets were selected as
wiring centres when the CSC installed its single-mode fibre
cable plant in Year 2002 in preparation for a major network
upgrade) for interconnecting the distribution switches at 5/F
of the Academic Building and the core switch at SCR.
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As fibre cables had already laid from every end-user edge switch
to the corresponding distribution switches at 5/F of the Academic
Building and to the same at MCR. When all the above steps have
been done, with an additional Internet link to be installed
inside the SCR, each user will then have two connection paths
to Internet, one transits through the MCR and one through the
SCR thereby providing users with a non-stop Internet service.
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Replicate an identical set of servers
as those in the MCR for providing services such as DNS, Active
Directory and LDAP.
As such, even when the Internet link or the network inside the MCR
is disrupted under a disaster, the Internet link inside the SCR
will keep the Internet services accessible by our users. With
full redundancy in network cabling, switches, Internet link provided
at both the MCR and the SCR, other critical IT services can also
be made non-stop through additional servers and storage to be
installed at the SCR.
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