Traffic Engineering

Question 1

Traffic Engineering

Answer 1

Process of re configuring the network the network in response to changing traffic loads to achieve operational goal

Question 2

3 steps of traffic engineering

Answer 2

Measure, Model, Control

Question 3

Traffic Optimization

Answer 3

Input
Network Graph (nodes / links)
Traffic matrix (router to router)

Output
Set of link weights for optimizing routes

Question 4

Objective Function

Answer 4

Traffic optimization goal

Question 5

Interdomain TE goals

Answer 5

Predictability
Limit neighbor influence
Reduce routing change overhead

Question 6

Achieving Interdomain TE goals

Answer 6

Predict -> no globally visible changes
Neighbor Influence -> Consistent adverts
Reduce overhead -> group prefixes

Question 7

Data Center Characteristics

Answer 7

Multi tenancy
Elastic Resources
Flexible service management

Question 8

Data Center Topology

Answer 8

Core Layer (top)
Aggregation Layer (middle)
Access Layer (bottom)

Question 9

Scale Problem

Answer 9

Core layer sees significantly greater amounts of traffic than access layer

Question 10

Pseudo MAC addresses

Answer 10

Allows creation of hierarchical network

Intercept ARP maps MACs to pseudo MACs

Question 11

Valiant Load Balance

Answer 11

Servers randomly select intermediate connection point to spread traffic out across servers in a data center

Question 12

Jellyfish topology

Answer 12

Random Regular Graph

Random: randomly selected from regular graphs
Regular: Each node has same degree
Graph: Switches are nodes

Question 13

Jellyfish Goals

Answer 13

More servers reachable along shorter paths

Question 14

TE what can be measured

Answer 14

Link saturation
Latency
Cost

Question 15

TE implement control

Answer 15

Adjust link weights to change traffic flows

Use SDN to control routes

Question 16

How do pods and pseudo MACs improve scalability

Answer 16

They allow the creation of hierarchy on a flat network

Allows smaller switch tables because only pseudo MACs (pod IDs) need to be stored

Question 17

Jellyfish advantages

Answer 17

Network load balancing

Higher capacity

Shorter paths

incremental expansion

Question 18

Jellyfish disadvantages

Answer 18

Does not handle heterogenous devices well

Potential long calbe runs between devices

Question 19

PortLand Fabric Manager

Answer 19

Fabric Manager responsible for maintaining network configuration soft state

Soft state performs ARP, multicast, fault tolerance

Fabric Manager is a user process running on a dedicated machine

Question 20

Pseudo MAC process

Answer 20

Components
pod, position, port, VM ID

Provides hierarchical structure to decrease switch port tables

Question 21

Jellyfish generation

Answer 21

N = Number of switches
k = number ports per switch
r = number ports used to connect to switches

Random Regular Graph(N,k,r)