Computer Services Centre

Indian Institute of Technology Delhi

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IIT Delhi new network backbone

This page gives an overview of the new 10G network backbone architecture at IIT Delhi.


Architecture of the new network


In the current phase, IITD has only upgraded the routers and switches for internet access, and the core and distribution network and has replaced the existing multimode fiber with new single mode fiber. This has made the backbone ready for dual redundant connectivity and 10 Gbps.

The access network, consisting of approximately 250 edge switches and extensive passive UTP cabling in the departments, hostels and blocks, has not been upgraded in the current phase to avoid massive disruption of services and also due to cost considerations. Our network backbone is 10 Gbps ready, and the access switches can now be replaced whenever there is a need to provide 10 Gbps connectivity to specific laboratories and locations.

The new design uses upgraded distribution switches at layer 3. This ensures restriction of broadcast domains to localized academic units and prevents broadcast traffic from all VLANs reaching the core routers.

In what follows we provide a brief description of the active components in the new design.

Internet access routers, firewall and core switches

The infrastructure for internet access, firewall and core switches are given in the figures below. The external routers, firewall and core switches are in redundant active-active cluster configuration. When our new main data centre (DC) and the disaster recovery data centre (DR) are ready, one of each will be located in the main data center and the other one will be located in the active secondary disaster recovery site. This will ensure that the internet connectivity remains unhampered even if one of the two sites goes down. Currently both set of equipments are located in the CSC.

The core switches have been upgraded to 10 Gbps ready Nexus 5596UP's. When the DC and the DR sites are ready the core switches will be upgraded to Nexus 7010's.

It is envisaged that the internet access routers, firewall and core switches are the minimal set of equipment in the CSC datacenter and the disaster recovery site that will never be switched off, even in case of failures elsewhere.


The diagram also shows the additional switches to be installed in the CSC data center and the disaster recovery site to connect the CSC server farms and storage equipment.

Distribution network for the academic area

The logical diagrams for the distribution network in the academic area are shown in the following three figures. There is redundant connectivity from all the distribution switches in the academic areas within IITD to both the internal core routers to ensure fault tolerance.

The entire connectivity is through single-mode fiber (10 Gbps).

All the distribution switches in the academic have been upgraded to 10 Gbps ready layer 3 4507's.




Access network in the academic area

A typical edge connectivity in a departmental location is shown below. This part is largely unchanged from the previous design. The main distribution switches are 10 Gbps ready and the individual laboratories and other departmental locations can be upgraded to 10 Gbps as and when there is a need.


Distribution network for the hostels

The logical diagram for the hostel distribution network is presented in figure below. Each hostel distribution switch (10 Gbps, layer 3) has dual redundant connectivity to a pair of aggregation switches to be located at the DC and the DR site respectively when they are ready. Currently both the aggregation switches are located in CSC. The aggregation switches, in turn, have dual redundant connectivity to the core switches.


Access network in the hostel area


Please refer to the figure above for a typical example (Zanskar) of a hostel access network. This part is also largely unchanged. The distribution switches have been upgraded to [3750X]'s which have dual 10G connectivity directly to the hostel aggregation switches in DC and DR.

Design of the residential network for 1200 homes

IITD has decided to adopt GPON technology for campus residential network using passive splitters (2 x 32 way). The detailed technical specifications of the GPON active equipment are yet to be finalised, but they will broadly include:

  1. An Optical Line Terminal (OLT) equipment with 1200+ terminations to be located at the data centre. The OLT should support a minimum of 400 Gbps backplane, 56 Gbps uplink capacity and at least two redundant switch cards with 8 x 1 GbE + 2 x 10 GbE uplinks.
  2. Voice over IP support over existing analog phones.
  3. 1200+ Optical network terminals (ONT) to be located at user residences, each with at least 4 fast ethernet ports, at least one RJ11 port for telephone.


Design of the passive fiber network and the fiber layout

The passive design consists of three rings of 12 tubes of 12 core fibers, one each for the east campus, the central academic campus and the west campus. Each ring passes through both the primary data centre site (DC) and the secondary disaster recovery site (DR). Currently both ends terminate at the CSC. Finally all fibers (3 x 144) will also terminate both at the primary and the secondary sites. 4/6 cores are be terminated at each active distribution site, out of which two each connect to the primary and the secondary sites respectively.

The physical routing of the three rings along with the details of the connectivity at various locations can be seen by opening IITDNetwork.kmz (N.C.Kalra) using the Google earth application. A more detailed GIS map of the fibre is being prepared.

Last Updated on Thursday, 05 January 2017 21:26