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Network and Infrastructure

Non-stop Internet Service and Network Connectivity

by C Y Kwok

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:

  • a redundant set of network cables and switches along the connection paths which are originated from users’ switches and terminated at switches inside SCR
  • the necessary network services such as DNS, Active Directory, LDAP etc.
  • other additional servers and storages and
  • 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:

  • 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.
  • 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.
  • 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.
  • 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.