Quiz #3

Question 1

What are four limitations to agility in data centers?

Answer 1

1. Insufficient network capacity for connecting the servers
2. Fragmented server pool (network congestion and hotspots).
3. Network flooding of one service affecting other services
4. IP addresses are statically bound to the servers

Question 2

What are the objectives of VL2? Select all that apply

Answer 2

1. Uniform Capacity (independent of topology, server-server communication limited only by NICs connected to the servers)
2. Performance Isolation for the services (the traffic of one service does not affect other services)
3. Flexible assignment of IP addresses to Ethernet ports to support server mobility commensurate with service requirements

Question 3

What are limitations of conventional data center

networks?

Answer 3

1. Dependence on high-cost proprietary routers (in connecting the data centers resources)
2. Extermely limited server-to-server capacity.
3. Huge variance in available bandwidth between servers depending on their location

Question 4

What are the characteristics of traffic patterns in

data center networks? Select all that apply

Answer 4

1. Traffic patterns are unpredictable

2. Traffic patterns are uncorrelated

Question 5

Why does probabilistic flow distribution work well (enough) for data center networks?

Answer 5

1. Enough capacity in
   the network for individual flows
2. Commodity switch-to-switch links are substantially thicker (~10x) than the maximum thickness of a flow.

Question 6

What is flat IP addressing?

Answer 6

Flat IP architecture provides a way to identify devices using symbolic names, unlike the hierarchical architecture such as that used in “normal” IP addresses.

Question 7

How is flat IP addressing accomplished in Azure VL2

switching fabric?

Answer 7

separate the name and the location & resolution server that does the mapping between name and location.

??? Use a nameserver to resolve the address?

??? Use a central authority outside the data center to issue IP addresses to the apps?

Question 8

What is Valiant Load Balancing for packet routing in a

data center network fabric?

Answer 8

Flow-based random traffic indirection in multipath scenarios.

*This is the solution to get uniform high capacity between servers.

Question 9

What is the meaning of layer-2 semantics in data center

networks?

Answer 9

Packet forwarding in the switches is based on link layer protocol.

*Basically the communication latency and the throughput should be bound by the network interface speeds of the source and destination

Question 10

What is the meaning of performance isolation?

Answer 10

The performance of an application is unaffected by other applications running concurrently with it

Question 11

What does VL2 stands for? where is incorporated?

Answer 11

VL2 stands for Virtual Layer 2 switch. This solution is incorporated in the Azure networking fabric.