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72 lines
2.1 KiB
Markdown
72 lines
2.1 KiB
Markdown
---
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title: "25-advanced-topics"
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aliases:
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tags:
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- cosc203
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- lecture
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sr-due: 2022-10-25
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sr-interval: 3
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sr-ease: 250
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---
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# Datacenter networks
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- 10's to 100's of thousands of hosts, often closely coupled, in close proximity
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- e-business :(e.g., amazon)
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- content servers: youtube etc
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- search engines, data mining (e.g., google)
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- challenges
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- multiple applications, each server many clients
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- reliability
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- managing/balancing load
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- procesing, networking, data bottlenecks
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network elements
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- server racks, 20-40 server blades: host
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- Top of Rack (TOR) switch
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- Tier 2 switches: connect to ~16 TORS below
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- tier 1 switches connect to ~16 T-2s below
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- border routers: connections outside
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- 
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- multipath communcation
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- rich interconnecitions so many routes
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- increased throughput
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- increased reliability through redundancy
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application-layer routing
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- load balancer: app-layer routing
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- recieves external client requests
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- directs workload within data center
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- returns results to client (data center internals are hidden)
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- 
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protocols
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- similar to TCP/IP protocols
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- link layer
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- RoCE: remote DMA (RDMA) over converged internet
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- direct memory access
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- communcation between memory of different computers
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- transport layer
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- ECN (explicit congestion notification) used in transport layer congestion control
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- experimentation with hop-by-hop (backpressure) congestion
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- routing management
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- SDN widely used
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- place related servers, as close as possible together
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# Software Defined networks
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- separate control plane and data plane
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- monollithic router contains switching hardware, runs proprietary implementation of internet standard protocols in proprietary router
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- different "middleboxes" for different network layer functions:
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- firewalls, load balancers, NAT boxes
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logically centralized control plane
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- easier network management: avoid router misconfigs, greater flexibility of traggic flows
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- table based forwarding allows "programming" routers
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- compute tables centrally and distribute
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- open implementation of control plane
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