Transcript BGP AS Number Exhaustion Geoff Huston Research activity supported by APNIC March 2003 The Problem    The 16 bit AS number field in BGP has 64,510 available.

BGP AS Number Exhaustion
Geoff Huston
Research activity
supported by APNIC
March 2003
The Problem



The 16 bit AS number field in BGP has
64,510 available values to use in the
Internet’s public routing space
Some 30,000 AS numbers have already
been assigned by the RIRs
This BGP protocol field will be
exhausted at some point in the future
The Solution

Use a 32 bit field for this value


draft-ietf-idr-as4bytes-06.txt describes how
This is proposed for publication as an
experimental RFC
The Issue

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
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 2 – 3 years to undertake this smoothly
So we’d like to know when we have 3 years to
go before we run out of AS numbers
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
The BGP Routing Table
Announced AS’s
BGP Table - AS Count
16000
14000
12000
10000
BGP Table
8000
6000
4000
2000
0
Sep-96
Sep-97
Sep-98
Sep-99
Sep-00
Sep-01
Sep-02
Sep-03
The BGP Routing Table
Growth Projections
60000
50000
40000
Exp Projection
Linear Projection
RIR Assignments
30000
20000
10000
May 2013
Feb 2008
Jan-14
Jan-12
Jan-10
Jan-08
Jan-06
Jan-04
Jan-02
Jan-00
Jan-98
Jan-96
Jan-94
Jan-92
Jan-90
0
IANA AS block Allocations
IANA AS Allocations
35000
30000
25000
20000
IANA AS Allocations
15000
10000
5000
0
Jan-90
Jan-91
Jan-92
Jan-93
Jan-94
Jan-95
Jan-96
Jan-97
Jan-98
Jan-99
Jan-00
Jan-01
Jan-02
Jan-03
From the IANA AS number Registry
IANA AS Allocation Projection
60000
50000
40000
IANA Allocations
Exp Projection
Linear Projection
30000
20000
10000
Nov 2010
May 2007
Jan-12
Jan-10
Jan-08
Jan-06
Jan-04
Jan-02
Jan-00
Jan-98
Jan-96
Jan-94
Jan-92
Jan-90
0
RIR Assignments
RIR Assignments
25000
20000
15000
RIR Assignments
10000
5000
0
Jan-90
Jan-91
Jan-92
Jan-93
Jan-94
Jan-95
Jan-96
Jan-97
Jan-98
Jan-99
Jan-00
Jan-01
Jan-02
Jan-03
From the RIR stats reports
RIR Projection
60000
50000
40000
Exp Projection
Linear Projection
RIR Assignments
30000
20000
10000
May 2013
Feb 2008
Jan-14
Jan-12
Jan-10
Jan-08
Jan-06
Jan-04
Jan-02
Jan-00
Jan-98
Jan-96
Jan-94
Jan-92
Jan-90
0
Combining these views
60000
50000
IANA
IANA EXP
IANA Linear
RIR
RIR Exp
RIR Linear
BGP
BGP exp 02
BGP Linear 02
40000
30000
20000
10000
14
13
12
11
10
09
08
07
06
05
04
03
02
01
00
99
98
97
96
95
94
93
92
91
90
0
Combined View + differences
35000
30000
25000
IANA
RIR Assigned
BGP Announced
NOT assigned
NOT Announced
20000
15000
10000
5000
0
Jan-90
Jan-91
Jan-92
Jan-93
Jan-94
Jan-95
Jan-96
Jan-97
Jan-98
Jan-99
Jan-00
Jan-01
Jan-02
Jan-03
Observations


RIRs operate with an allocation buffer
of around 5,000 numbers
10,000 AS numbers (40% 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 2 byte AS
number pool exhaustion predictions
Announced and Unannounced ASs
16000
14000
12000
10000
Announced
Unannounced
8000
6000
4000
2000
Oct-02
Oct-01
Oct-00
Oct-99
Oct-98
Oct-97
Oct-96
0
Unannounced : Announced AS’s
Ratio Unann:Ann
2.25
2
1.75
1.5
1.25
Ratio Unann:Ann
1
0.75
0.5
0.25
0
Oct-96
Oct-97
Oct-98
Oct-99
Oct-00
Oct-01
Oct-02
Oct-03
Oct-04
Oct-05
Trend:
unannounced : announced ratio
Ratio Unann:Ann
2.25
2
1.75
1.5
1.25
Ratio Unann:Ann
1
0.75
0.5
0.25
0
Oct-96
Oct-97
Oct-98
Oct-99
Oct-00
Oct-01
Oct-02
Oct-03
Oct-04
Oct-05
Jan-03
Sep-02
May-02
Jan-02
Sep-01
May-01
Jan-01
Sep-00
May-00
Jan-00
Sep-99
May-99
Jan-99
Sep-98
May-98
Jan-98
Sep-97
May-97
Jan-97
Sep-96
May-96
Jan-96
Sep-95
May-95
Jan-95
Sep-94
May-94
Jan-94
Sep-93
May-93
Jan-93
Sep-92
May-92
Jan-92
Sep-91
May-91
Jan-91
Sep-90
May-90
Jan-90
Announced / Unannounced
Distribution by Date
600
500
400
300
UnAnnounced
BGP Announced
200
100
0
Distribution by AS Number Range
100%
90%
80%
70%
60%
Unassigned
NOT Announced
Announced
50%
40%
30%
20%
10%
0%
1
11
21
31
41
51
61
71
81
91
101 111 121 131 141 151 161 171 181 191 201 211 221 231 241 251 261 271 281
Observations

Low AS number ranges have the highest
unannounced / announced ratios


Reclamation of unused AS numbers in the low
number ranges is likely to be a useful exercise
Recent assignments show a 60%
announcement utilization ratio for AS
numbers


LIR staging point factors
Inadequate incentives to return if no immediate
requirement for deployment
Forecast
1 – AS recovery in effect - 2011
70000
60000
50000
IANA
RIR
BGP Projection
BGP
Unassigned
Unrouted
40000
30000
20000
10000
0
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
Forecast
2 – No significant recovery – 2009
70000
60000
50000
IANA
RIR
BGP Projection
BGP
Unassigned
Unrouted
40000
30000
20000
10000
0
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
Current AS Forecast

The available AS number pool will exhaust in
the timeframe of 2009-2011 if current AS
use trends continue
2009


no significant reclamation in old AS number space
No coordinated effort to increase utilization density of
AS numbers
2011

reclamation and increased deployment efficiency