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

Question 2

Why traffic load? Operator might want to ____

Answer 2

Peer ratios
relieve congestion
balance load

Question 3

Self managing ip networkings

Answer 3

TCP

Routing

Question 4

Self managing ip networkings: Problem

Answer 4

May not run efficiently

Question 5

Intradomain TE: Tuning link weights

Answer 5

intradomain: routers flood information to learn topology

operator can configure the weights on links to help decide the flow of that information through the network to help avoid congestion

Question 6

Traffic Engineering 3 steps

Answer 6

Measuring the network
Forming a model
Reconfiguring the network to assert control

Question 7

Measure

Answer 7

Topology

Traffic

Question 8

Intradomain TE: Optimization

Answer 8

Input: Graph G(R, L)
Output: Set of link weights wl

Question 9

Graph G(R, L) variable meanings

Answer 9

R = routers
L = links

Question 10

cl

Answer 10

capacity of l

Question 11

Traffic matrix Mij

Answer 11

traffic from router i to router j

Question 12

Objective function

Answer 12

Objective: minimize f(ul/cl)

Question 13

Utilization function

Answer 13

ul/cl

traffic on link/capacity

Question 14

Intradomain routing

Answer 14

within a domain (ISPs, campus, datacenter)

Question 15

interdomain routing

Answer 15

between networks

Question 16

interdomain traffic engineering

Answer 16

Using new/upgraded edge links
Alleviating congestion on edge links
cloning end to end path

Question 17

Goals for interdomain traffic engineering

Answer 17

Predictability
Limit influence of neighbors
Reduce overload of routing changes

Question 18

How to be predictable

Answer 18

No globally visible changes

Question 19

How to limit influence of neighbors

Answer 19

consistent adverts, limit AS path

Question 20

How to reduce overhead of routing changes

Answer 20

group prefixes

Question 21

multipath routing

Answer 21

operator can establish multiple paths in advance

Question 22

traffic splitting

Answer 22

change % of traffic sent on path

Question 23

Data center networking Characteristics

Answer 23

multi tenancy
elastic resources
flexible service management

Question 24

DAta center networking challenges

Answer 24

traffic load balance
support for virtual machine migration
power savings
provisioning the network when changes occur
security

Question 25

Data Center topology

Answer 25

1. Each pod has address

2. Each server has a psuedo mac corresponding to pod

Question 26

Data center TE

Answer 26

Limited server to server capacity - links at the top of a fat tree topology are over subscribed
Fragmentation - significant’y lowering utilization

Question 27

Valiant Level Balance goals

Answer 27

1. Spread Traffic

2. Location independence

Question 28

Jellyfsh

Answer 28

Networking data centers randomly

Question 29

Jellyfish Goals

Answer 29

High throughput (Big data)
incremental expandability (easy replacement of servers)

Question 30

Jellyfish problems

Answer 30

Structure constrains expansion

Question 31

Jellyfish topology is called

Answer 31

randomly regular graph

Question 32

randomly regular graph

Answer 32

randomly selected from regular graphs

Question 33

regular graph

Answer 33

each node has the same degree

each switch is a node

Question 34

Constructing a Jellyfish topology

Answer 34

1. Pick a random switch pair where they have a free port to become neighbors
2. join with link.
3. repeat until no further links can be added