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 ? AS2AS1 NetA

Terminology – Cont. Inbound decision I want to receive inbound traffic for NetB via SA1 link only AS2AS1 NetB 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 Backup Set local pref = Set local pref = 100 Gateway of last resort is

Setting Default Routers – Cont. AS1 AS2 Primary Backup Set local pref = Set local pref = 100 Gateway of last resort is

Setting Default Routers – Cont. Statically Set Defaults –IP of next-hop gateway Example : IP –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 Static Incoming 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

C2C2 C3C5C4 NAP (X,Y)(Z,W) W: 200 Z: 200 Rest : 250 Y: 200 X: 200 Rest : 300 C5: 300 C4: 300 Rest : 250 C3: 300 C2: 300 Rest : 200 Metrics Preference Default-1 Primary Default-2 Backup 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 ISP Customer

Scenario 2 – Cont. Balancing between two routers sharing multiple paths RTA NetX RTB BGP Session Link2 Link1

DestinationNext Hop NetX (best) NetX RTA’s BGP Table RTA NetX RTB BGP Session Link2 Link1

DestinationNext Hop NetX /24Link1 RTA’s Routing Table RTA NetX RTB BGP Session Link2 Link1

DestinationNext Hop NetX RTA’s BGP Table BGP Session RTA NetX RTB Link2 Link

DestinationNext Hop NetX /24Link /24Link2 RTA’s Routing Table BGP Session RTA NetX RTB Link2 Link

Scenario 3 : Multihoming to Different Providers Default only, Primary and Backup NAP /16 Pref= /16 Pref= /16

Scenario 3 – Cont. Default, Primary and Backup plus partial routing

NAP Customer IBGP Default-1 primary Default-2 backup Partial Routes

Scenario 3 – Cont. Default, Primary and Backup plus full and partial routing

NAP Customer IBGP Primary Backup Partial Routes

Scenario 3 – Cont. Customer Inbound Traffic

NAP /24 – /24 – /24 – /24 – /24 Customer IBGP AS100 AS200 AS300

Scenario 4 : Customers of the Same Provider with Private Link Private link used as pure backup NAPAS1AS3AS2 Pref=200 Pref=100 Backup

Scenario 4 – Cont. Private link used as primary link NAP AS1 AS3 AS2 Pref=300 Pref=200 AS3 Routes Updates that do not contain AS3 Pref=100

Scenario 5 : Customers of Different Providers with a Private Link NAP ISP1 ISP2 AS2AS1

Community Approach ISP routes - 60 Customer transit routes - 40 Customer local routes ISP1 ISP2 AS1 AS2 AS

PatternCommunityLocal Pref. Customer local routesNone100 Customer transit routes400:4040 ISP routes400:6060 ISP routes - 60 Customer transit routes - 40 Customer local routes AS1 AS2 AS ISP2ISP1

AS Path Manipulation AS2’s routes via ISP2 AS_Path: AS2’s routes via AS1 AS_Path: ISP1ISP2 AS1 AS2 AS400