The Gathering Technical blog

Network design TG17

15 Apr 2017, by from Tech:Net

The Gathering has almost come to an end and it’s about time we posted some details about our network design.
Network Design

Network design

Our network is designed in the traditional three-layered hierarchical model with the core, distribution and access layer where L3 is terminated at our distribution.

Core layer
The core L3 switches consists of 2x Juniper QFX5100 in a virtual chassis, which is Junipers stacking technology. In addition to provide our distribution with uplinks, the core switch also connects our 80Gig backbone ring with our stand and border router.
Between our border router the internet we have an inline Juniper SRX5800 which is capable of pushing 2Tbps worth of firewall throughput(!). This is where we terminate our BGP peering with Telenor and do route redistribution to OSPF, making the SRX our OSPF ASBR.

Distribution Layer
The L3 distribution switches consists of 3x Juniper EX3300 in a virtual chassis per distribution. It connects to the core using 2x 10Gbps singel-mode transceivers patched into our MPO cassettes pulled from the ceiling. The distro redistributes its connected routes into the OSPF area and advertises it to the core.

Access layer
The L2 access switches consists of 144+ Juniper EX2200 with a 3x 1Gbps connection to our distribution. To protect our network at the edge, we run a series of security features collectively called first-hop security. This takes care of a lot of potential issues such as loops, spoofing and ARP-poisoning.

One of the design choices this year was to turn our backbone ring, which traverses the entire arena, into a virtual chassis instead of separate routers. This effectively means that it becomes a distribution switch for our crew network. This makes it easy for us to provision edge/access switches to our sponsors and crew areas. As a result we have for the first time ever provisioned our entire access network. Not a single access switch has been configured manually this year!

Internet capacity

TL;DR – 40Gbps…

At TG16 we suffered several DDoS attacks towards our network and even our website ( In order to be able to handle a potential DDoS attack this year we decided to upgrade our internet capacity from 40Gbps to 40Gbps + 10Gbps, where the newly added 10Gbps-link would be reserved for our production environment. Instead of dedicating a single physical interface, we decided to include the interface in our aggregated interface and rate-limit our participants network to 40Gbps. This way we keep our production network alive when our participants network gets lit up.


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