FIB Aggregation with SMALTA

Zartash UzmiAhsan TariqPaul Francis

draft-uzmi-smalta-00

Introduced at IETF 76 draft-zhang-fibaggregation Level 1-4

SMALTA == Level 5 Better aggregation No extra-routable space Comparable update processing

For community information

FIB Aggregation Work

04/21/23 2FIB Aggregation with SMALTA

RIB

Primary Routes

FIB

Original Table

Aggregated Table

FIB

Normal Operation

With Aggregation

Comparative Summary

04/21/23 FIB Aggregation with SMALTA 3

Extra-routable space

(Whiteholing)

% Original*1

Level 1 N 68%

Level2 N 49%

Level 3 Y -

Level 4 Y -

SMALTA N 39%

SMALTA-ER(future)

Y -

*1 From various RIB snapshots (from routeviews) since 2004

FIB Aggregation: basic idea

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/22

/23

A

Exploit aggregation opportunities over entire Table

Original Table Aggregated Table

A

/22

A

/23/23

AA

/22

ALevel 2SpecificsCombines(beyond L1)

Level 1SpecificsRemoved

Where does SMALTA stand?

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AggregationOpportunities

Updates

Whiteholing

Level 1 Specifics removed Y N

Level2 Specifics combined Y N

Level 3 Specifics combinedover holes

Y Y

Level 4 Y Y

ORTC [1999]

Exploits all: Optimal N N

SMALTA Exploits all (~ORTC)

Y N

RIB snapshot Aggregate FIB: One-shot Algo

BGP updates Aggregated table: Update Algo

One-shot and WITHDRAW

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Original Aggregated (SMALTA)C

B

A

A

C

A

A

A

BWithdraw

Withdraw

C

B A

C

A

B B

With Level 1-4Can’t aggregate

any further!

Deaggregation Opportunities to aggregate more

SMALTA Update

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1. How far aggregated you are after N updates?

2. How many RIB-to-FIB downloads per update?

Each update may result in justONE change in Original Table

RIB-to-FIB downloads: Exactly 1 (No Aggregation) 0/1/more (With Aggregation)

Year #updates*1

SMALTA Level 1

Level 2

2004 1153577 0.56 0.99 0.93

2005 1166839 0.49 0.79 0.77

2006 1718496 0.64 0.99 0.89

2007 1518776 0.54 0.73 0.71

2008 2235465 0.56 0.93 0.80

After applying a full-day update trace:SMALTA loses between 1-6% of fully-aggregated state

(one-shot)Measured for numerous routing tables across different

years!

SMALTA One-Shot (300-400ms)~3-4x more processing than L1 and L2Applied very infrequently

SMALTA Update~ same processing time as L1 and L2Fewer avg. RIB-to-FIB downloads

Remarks

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COMMENTS / QUESTIONS

BACKUP SLIDES

Basic Idea for Updates

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Example 2: Aggregate specifics [having same next hop] – Level2

/23/23

A

AA A

/22

With

dra

wWith

dra

w

One-shot + ANNOUNCE + WITHDRAW

04/21/23 12FIB Aggregation with SMALTA

Original Aggregated(with SMALTA)

C

B

A

A

C

A

BAnnounce(

Q)Announce(

Q)

C

B

A

A

C

A

B QQ What if?

Withdraw

How far aggregated you are after N updates?

How long does it take to incorporate updates?

How many RIB to FIB downloads per update?

Incremental Updates: Analysis

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Can’t aggregate entire table on every update One-shot aggregation

Take current snapshot of RIB and Aggregate On “significant” routing changes (e.g., BGP hard reset) Perform a monolithic download after one-shot

To reflect BGP updates in FIB Incremental updates to aggregated table

Practicalities

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Problem well-understood in GROW draft-zhang-fibaggregation

Status: FIB Aggregation Work

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RIB

Primary Routes

FIB

RoutingUpdates

Original Table [RIB]

Aggregated Table

FIB

RoutingUpdates

Normal Operation With Aggregation

IGP IGP

Year #(entries)Orig. Table

# Level1Aggregati

on

# Level2Aggregatio

n(includes

L1)

# SMALTA(one-shot)

2004 160818 103565 69572 54340

2005 176474 109169 73169 55801

2006 203082 139763 96993 75357

2007 240162 161147 110065 83282

2008 269532 178676 117139 84170

SMALTA One-shot1,2 (no policy)

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1. Tables from a routeviews “collection” router [41-46 peers]2. Policy (for best path): shortest AS path length preferred

Average Size 66% 44% 34% (of original)

SMALTA Update: time consumed

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Year Avg. time perUpdate (Level1)

Avg. time perUpdate (Level2)

Avg. time per Update

(SMALTA)

2004 2.9μs 2.9μs 2.8μs

2005 3.0μs 2.9μs 2.9μs

2006 3.0μs 2.9μs 3.0μs

2007 3.0μs 3.1μs 3.0μs

2008 3.0μs 3.0μs 3.1μs

How long*3 does it take toincorporate an update?

*3 Dependent on Platform and implementation (reported for comparison only)

SMALTA: RIB to FIB Downloads(15-min update trace)

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Year #updates*1

Avg. # RIB toFIB

downloads

Max # RIB toFIB

downloads

Prefix forMax

2004 160818 1.0494 300 /8

2005 176474 1.0962 157 /8

2006 203082 0.966 499 /8

2007 240162 1.3141 376 /11

2008 269532 0.4031 64 /8

*1 From a 15-minute update trace