10 - Traffic Engineering

Question 1

Traffic Engineering

Answer 1

Process of reconfiguring the network in response to changing traffic loads, to achieve some operational goal.

• Peering ratios
• Relieve Congestion
• Balance load

Question 2

“Self-management”

Answer 2

TCP, routing

Question 3

How should routing adapt to traffic?

Answer 3

• Avoid congested links

- Satisfy application requirements such as delay

Question 4

Intradomain TE: Tuning Link Weights

Answer 4

• Routers flood information to learn topology
• Operator configures link weights
• Inversely proportional to capacity
• Proportional to propagation delay
• Network-wide optimization

Question 5

3 Steps of Traffic Engineering

Answer 5

• Measuring the network to figure out the current traffic loads
• forming a model of how configuration affects the underlying paths on the network
• Reconfiguring the network to exert control over how the traffic flows through the network

Measure, Model, Control

Question 6

Intradomain

Answer 6

Within a domain (e.g., ISP, campus, datacenter)

Question 7

Interdomain

Answer 7

between domains

Question 8

Interdomain Traffic Engineering

Answer 8

• Alleviating congestion on edge links
• Using new/upgraded edge links
• Changing end-to-end path

Reconfiguration of BGP

Question 9

Goals of Interdomain TE

Answer 9

1. Predictability
   - > no globally visible changes
2. Limit influence of neighbors
   - > consistent adverts, limit AS path
3. Reduce overload of routing changes
   - > group prefixes

Question 10

How can source router adjust paths?

Answer 10

Alternating b/w forwarding table entries

Question 11

Data Center Networking

Answer 11

Characteristics of a data center
1. Multi-tenancy
  \+ amortization of cost
  - security, resource isolation
2. Elastic resources
3. Flexible service management
--> workload movement, migration
    enabler: virtualization

Question 12

Data Center Networking Challenges

Answer 12

• Traffic load balance
• Support for virtual machine migration
• Power savings
• Provisioning
• Security

Question 13

Data Center TE

Answer 13

• Limited server-to-server capacity
  
  • > links @ “top” of fat tree topology are over-subscribed
• Fragmentation

Question 14

Goals of Valiant Load Balancing in VL2 network

Answer 14

1. Spread traffic (evenly across servers)

2. Traffic load is balanced independently of the destinations of the traffic flows

Question 15

Jellyfish

Answer 15

Goals:

• High throughput -> big data
• Incremental expandability -> easy replacement of servers

Problem: Structure constrains expansion