Redundancy, Symmetry and Load Balancing

Presented by

Sagi Shporer

Terminology

Redundancy

Symmetry

Load Balancing

Terminology – Cont.

Outbound decision

Which way should the traffic be sent to NetA ?

AS2

AS1NetA

NetA

Terminology – Cont.

Inbound decision

I want to receive inbound traffic for NetB via SA1 link only

AS2

AS1NetB

NetC

Terminology – Cont.

Load Balancing – choosing ISP

ISP2

Customer

ISP1

Setting Default Routers

Gateway of last resort

Dynamic Learned Defaults

Statically Set Defaults

Setting Default Routers – Cont.

AS1 AS2

Primary

Backup2.2.2.2Set local pref = 50

1.1.1.1Set local pref = 100

Gateway of last resort is 1.1.1.1

Setting Default Routers – Cont.

AS1AS2

Primary

Backup2.2.2.2Set local pref = 50

1.1.1.1

Set local pref = 100

Gateway of last resort is 1.1.1.1

Setting Default Routers – Cont.

Statically Set Defaults– IP of next-hop gateway

• Example : IP 201.1.2.3

– A network number• Example : The route to that network number is

learned dynamically

– A specific router interface• Example : Ethernet interface 0

Routing Tables

No Routes

Partial Routes

Full Routes

Specific Scenarios

Single-Homing

Multihoming to a Single Provider

Multihoming to Different Providers

Customers of the Same Provider with Backup Link

Customers of Different Providers with a Backup Link

Scenario 1 : Single-Homing

Customer

Default

ISP

StaticIncoming traffic

Outgoing traffic

Scenario 2 : Multihoming to a Single Provider

Default only, one Primary, one Backup

Provider

Customer

Default-2

Backup

Metric : 100

Default-1

Primary

Mertic : 50

Scenario 2 – Cont.

Default, Primary and Backup plus partial routing

C2

C3

C5

C4NAP

(X,Y) (Z,W)

W: 200Z: 200Rest : 250

Y: 200X: 200Rest : 300

C5: 300C4: 300Rest : 250

C3: 300C2: 300Rest : 200

Metrics

Preference

Default-1Primary

Default-2Backup

Customer

ISP

Scenario 2 – Cont.

Default, Primary and Backup plus full and partial routing– Full route on one link, and no route or partial

route on the other links

Scenario 2 – Cont.

Automatic load balancing

192.213.10.6192.213.10.5192.213.10.4192.213.10.3192.213.10.2192.213.10.1

135

246

ISP

Customer

Scenario 2 – Cont.

Balancing between two routers sharing multiple paths

11.11.11.1 11.11.11.2

10.10.10.1 10.10.10.2RTA

NetX

RTB

BGP Session

BGP Session

Link2

Link1

DestinationNext Hop

NetX10.10.10.2 (best)

NetX11.11.11.2

RTA’s BGP Table

11.11.11.1 11.11.11.2

10.10.10.1 10.10.10.2RTA

NetX

RTB

BGP Session

BGP Session

Link2

Link1

DestinationNext Hop

NetX10.10.10.2

10.10.10.0/24Link1

RTA’s Routing Table

11.11.11.1 11.11.11.2

10.10.10.1 10.10.10.2RTA

NetX

RTB

BGP Session

BGP Session

Link2

Link1

DestinationNext Hop

NetX12.12.12.12

RTA’s BGP Table

BGP Session

11.11.11.1 11.11.11.2

10.10.10.1 10.10.10.2RTA

NetX

RTB

Link2

Link1

9.9.9.9 12.12.12.12

DestinationNext Hop

NetX12.12.12.12

12.12.12.0/24Link1

12.12.12.0/24Link2

RTA’s Routing Table

BGP Session

11.11.11.1 11.11.11.2

10.10.10.1 10.10.10.2RTA

NetX

RTB

Link2

Link1

9.9.9.9 12.12.12.12

Scenario 3 : Multihoming to Different Providers

Default only, Primary and Backup

NAP 192.213.0.0/16

Pref=200192.213.0.0/16

Pref=100192.213.0.0/16

Scenario 3 – Cont.

Default, Primary and Backup plus partial routing

NAP

Customer

IBGP

Default-1primary

Default-2backup

Partial Routes

Scenario 3 – Cont.

Default, Primary and Backup plus full and partial routing

NAP

Customer

IBGP

PrimaryBackup

Partial Routes

Partial Routes

Scenario 3 – Cont.

Customer Inbound Traffic

NAP192.213.1.0/24 – 200 100

192.213.1.0/24 – 300 100 100

192.213.1.0/24 – 100

192.213.1.0/24 – 100 100

192.213.1.0/24

Customer

IBGP

AS100

AS200AS300

Scenario 4 : Customers of the Same Provider with Private Link

Private link used as pure backup

NAPAS1

AS3AS2

Pref=200

Pref=100

Backup

Scenario 4 – Cont.

Private link used as primary link

NAPAS1

AS3AS2

Pref=300

Pref=200AS3 Routes

Updates that do not contain AS3

Pref=100

Scenario 5 : Customers of Different Providers with a Private

Link

NAP

ISP1ISP2

AS2AS1

Community Approach

ISP routes - 60

Customer transit routes - 40

Customer local routes - 100

ISP1 ISP2

AS1 AS2

AS400

40100

60

PatternCommunityLocal Pref.

Customer local routesNone100

Customer transit routes400:4040

ISP routes400:6060

ISP routes - 60

Customer transit routes - 40

Customer local routes - 100

AS1 AS2

AS400

40100

60ISP2ISP1

AS Path Manipulation

AS2’s routes via ISP2 AS_Path: 500 1

AS2’s routes via AS1 AS_Path: 1 1 2

ISP1 ISP2

AS1 AS2

AS400