Transcript ASN Consumption

AS Consumption Patterns
Geoff Huston
APNIC
May 2005
1
AS Numbers
• The 16 bit AS number field in BGP has
64,510 available values to use in the
Internet’s public routing space
• Some 38,000 AS numbers have already
been assigned by the RIRs
• This number space will be exhausted at
some point in the future
2
32 Bit AS Numbers
• Use a 32 bit field for this value
• draft-ietf-idr-as4bytes-09.txt describes how
• This is proposed for publication as an
Experimental RFC
Has been in this state for some years. Unclear whether it
has stalled or just moving very slowly through the IETF
standards process.
3
The Issue – Transition Planning
• At some point we will need to start testing
various transition plans and vendor
implementations, set up a new AS
number registry, and commence
deployment of these extended length
protocol objects in BGP
4
When?
• Before we run completely out of 16 bit AS
numbers
• Need to allow a lead time for testing,
deployment of 4-byte AS BGP
implementations and development of
appropriate transition arrangements
• Allow some 3-4 years to undertake this
smoothly
• So we’d like to know when we have 4 years
to go before we run out of AS numbers
5
When?
• A number of views can be used to make
forward projections:
• The growth of the number of announced AS’s
in the BGP routing table
• The rate at which AS number blocks are
passed from IANA to the RIRs
• The rate at which RIRs undertake
assignments of As’s to LIRs and end users
6
The BGP Routing Table: Announced AS’s
Advertised AS count
25,000
20,000
Count
15,000
10,000
5,000
Date
7
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
0
The BGP Routing Table: Growth Projections
AS Projections from BGP data
65,536
57,344
49,152
AS Count
40,960
32,768
24,576
16,384
8,192
July 2014
Sept 2025
Date
Advertised
8
Exp Projection
Linear Projection
2026
2024
2022
2020
2018
2016
2014
2012
2010
2008
2006
2004
2002
2000
1998
1996
0
IANA AS block allocations to RIRs
IANA Allocations
40,000
35,000
30,000
Count
25,000
20,000
15,000
10,000
5,000
2006
2004
2002
2000
1998
1996
1994
1992
0
Date
9
From the IANA AS number Registry
IANA AS Allocation Projection
IANA Allocation Projections
65,536
57,344
49,152
40,960
32,768
24,576
16,384
8,192
July 2014
June 2011
IANA Allocations
10
Exp Projection
Linear Projection
2016
2014
2012
2010
2008
2006
2004
2002
2000
1998
1996
1994
1992
0
RIR Assignments
RIR Assignments
35,000
30,000
25,000
Count
20,000
There are some inconsistencies in the data
15,000
10,000
5,000
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
0
Date
11
From the RIR stats reports
RIR Allocation Projection
RIR Data Projections
65,536
57,344
49,152
Count
40,960
32,768
24,576
16,384
8,192
Aug 2014
Sept 2010
Date
Assignments
12
Exp-Projection
Linear Projection
2014
2012
2010
2008
2006
2004
2002
2000
1998
1996
1994
1992
0
13
Date
2026
2025
2024
2023
2022
2021
2020
2019
2018
2017
2016
2015
2014
2013
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
Count
Combining these views
AS Projections
65,536
57,344
49,152
40,960
32,768
24,576
16,384
8,192
0
Combined View + Differences
AS Status
40,000
35,000
30,000
Count
25,000
20,000
15,000
10,000
5,000
Date
IANA
14
RIR
BGP
RIR Pool
UnAdvertised
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
0
Observations
• RIRs operate with an allocation buffer of
an average of 5,000 numbers
• 12,348 AS numbers (39% of the
assigned AS numbers) are not
announced in the BGP table.
• Is this the result of old AS assignments
falling into disuse?
• Or recent AS assignments being hoarded?
• This pool creates uncertainty in AS number
pool exhaustion predictions
15
UnAdvertised and Advertised ASs
Advertised vs UnAdvertised
25,000
20,000
Count
15,000
10,000
5,000
Date
Advertised
16
UnAdvertised
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
0
UnAdvertised : Advertised AS’s
Unadvertised / Advertised Ratio
2
1.8
1.6
1.4
Ratio
1.2
1
0.8
0.6
0.4
0.2
Date
17
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
0
Trend: UnAdvertised : Advertised Ratio
UnAdvertised / Advertised Ratio Projection
2
1.8
1.6
1.4
Ratio
1.2
1
0.8
0.6
0.4
0.2
Date
18
2012
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
0
UnAdvertised / Advertised Distribution by Date
Unadvertised and Advertised ASes
600
500
Count
400
300
200
100
Allocation Date
Unadv
19
Adv
2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
0
Distribution by AS Number Range
AS Status - April 2005
256
224
192
160
128
96
64
32
ADV
20
UNADV
RIR
61440
57344
53248
IETF
49152
40960
IANA
AS Block (256)
45056
36864
32768
28672
24576
20480
16384
12288
8192
4096
0
0
UnAdvertised / Advertised Relative Proportion by Date
Unadvertised ASs (% of Allocated) by Date
100
90
80
70
Percent
60
50
40
30
20
10
Allocation Date
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2005
2004
2003
2002
2001
2000
1999
1998
1997
1996
1995
1994
1993
1992
0
Observations
• AS numbers age out and disappear
• 5% attrition rate per year
• Old (low) AS number ranges have the highest
unannounced / announced ratios
• Recent assignments take some 4 months to
be advertised
• LIR staging point factors
• Projections of AS number consumption should
include a factor for Unadvertised / Advertised
ratio that has a linear best fit (negative slope)
22
Selecting a Best Fit to the Data
• A Linear growth model will have a
constant first order differential
• An exponential growth model will have a
linear best fit to the log of the data
• The data set for the best fit is to a
smoothed (moving average) time series
of the cumulative sum of RIR AS
allocations
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Linear Model Fit
Allocations
32,000
31,000
30,000
Allocations
29,000
28,000
27,000
26,000
25,000
24,000
23,000
2003
2003.5
2004
2004.5
Date
24
2005
Linear Model Fit
AS Allocations - 1st order differential
18
16
AS's per day
14
12
10
8
6
2005
2004
2003
4
Date
25
Exponential Model Fit
Allocations
32,000
31,000
30,000
Allocations
29,000
28,000
27,000
26,000
25,000
24,000
23,000
2003
2003.5
2004
2004.5
Date
26
2005
Exponential Model Fit
1st Order Differential of Log(Allocations)
7
6
d log(allocations)/dt
5
4
3
2
1
2003
2003.5
2004
2004.5
Date
27
2005
2005.5
Combining Allocation and Advertised AS
Data Projections
AS Comsumption Projections
65536
57344
49152
40960
32768
24576
16384
8192
2026
2024
2022
2020
2018
2016
2014
2012
2010
2008
2006
2004
2002
2000
1998
1996
1994
1992
0
Date
Assigned
28
Advertised
Unadvertised
Linear-Alloc
Linear-Adv
Linear-UnAdv
Exp-Alloc
Exp-Adv
Exp-UnAdv
Current AS Use Projections
• The available AS number pool will exhaust in
the timeframe of 2010 - 2020 if current AS use
trends continue
2010
• No significant reclamation in old AS number space
• No coordinated effort to increase utilization density of AS
numbers
• Increasing consumption trend
• Most likely outcome as a best fit to post 2003 consumption
data
2020
• Extensive reuse of idle / unused AS numbers
• High use rate maintained
• Assuming a continued constant rate of demand
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Planning Considerations (again)
• Need to allow a lead time for testing,
deployment of 4-byte AS BGP implementations
and development and testing of appropriate
transition arrangements
• Allow some 3-4 years to undertake this smoothly
• So we’d like to know when we have around 4
years to go before we run out of AS numbers
• In the most likely consumption projection that
advance planning date looks like being in 2006
• In a more tempered growth environment this
may extend out to 2010
30