Routing20152015
RoutingGeoff Huston
APNIC

Through the Routing Lens

Through the Routing Lens
There are very few ways to assemble a single view of theentire InternetThe lens of routing is one of the ways in which information
relating to the entire reachable Internet is bought together
Even so, its not a perfect lens…

There is no Routing God!
There is no single objective “out of the system” view of theInternet’s Routing environment.
BGP distributes a routing view that is modified as it isdistributed, so every eBGP speaker will see a slightly different
set of prefixes, and each view is relative to a given location
So the picture I will be painting here is one that is drawn fromthe perspective of AS131072. This is a stub AS at edge of
the Internet, and this is an eBGP view.
You may have a similar view from your network.

28 Years of Routing the Internet

This is a view pulled together from each of
the routing peers of Route Views

2011: Address Exhaustion

2009: The GFC hits the Internet

2005: Broadband to the Masses
2001: The Great Internet Boom and Bust
1994: Introduction of CIDR

28 Years of Routing the Internet

This is a view pulled together from each ofthe routing peers of Route Views

2011: Address Exhaustion

2009: The GFC hits the Internet

2005: Broadband to the Masses
2001: The Great Internet Boom and Bust
1994: Introduction of CIDR

2015, as seen at Route Views

2015, as seen at Route Views

Average growth rateRouting Indicators for IPv4
Routing prefixes – growing bysome 47,000 prefixes per year

AS Numbers– growing by some
3,100 prefixes per year

Routing Indicators for IPv4
More Specifics are still taking up
one half of the routing table

But the average size of arouting advertisement is gettingsmaller

Routing Indicators for IPv4
Address Exhaustion is now
visible in the extent ofadvertised address space

The “shape” of inter-ASinterconnection appears to berelatively steady, as the Average
AS Path length has been steadythrough the year

What happened in 2015 in V4?
• From the look of the growth plots, its business as usual,despite the increasing pressure on IPv4 address availability• The number of entries in the default-free zone is now
heading to 600,000• The pace of growth of the routing table is still relatively
constant at ~50,000 new entries per year
– IPv4 address exhaustion is not changing this!

How can the IPv4 network continue
to grow when we are running outof IPv4 addresses?
We are now recycling old addresses back into the routingsystem
Some of these addresses are transferred in ways that arerecorded in the registry system, while others are being“leased” without any clear registration entry that describes
the lessee

Address “Age”
Address “age” in 20102% of all new addresses announced in 2010
were >= 20 years ‘old’ (legacy)
80% of all new addresses announced in 2010
were allocated or assigned within the past 12months

IPv4 Address Reuse
Address “age” in 2015

33 % of all new addresses announced
in 2015 were >= 20 years ‘old’(legacy)

20 % of all new addresses announced in 2015
were allocated or assigned within the past 12months

IPv4 in 2015 – Growth isSteady• Overall IPv4 Internet growth in terms of BGP is at a rate ofsome ~47,000 entries p.a.
• But we’ve run out of the unallocated address pools
everywhere except Afrinic• So what’s driving this post-exhaustion growth?
– Transfers?
– Last /8 policies in RIPE and APNIC?
– Leasing and address recovery?

IPv4: Advertised vsUnadvertised Addresses

IPv4: Unadvertised Addresses

IPv4: Unadvertised Addresses

This is not!

This is expected!

IPv4: Unadvertised Addresses

IPv4:Assigned vs RecoveredIPv4 in 2015
Approximately 4 /8s were assigned and advertised in 2015
– 2.3 /8s were assigned by ARIN
– 1 /8 assigned by AfriNIC

Up to 3 /8s were ‘recovered’ from the unallocated addresspool and advertised during 2015
–But 2/8s of addresses were withdrawn in the last two months ofthe year

The Route Views view of IPv6

World IPv6 Day
IANA IPv4 Exhaustion

2015 for IPv6, as seen at
Route Views

Routing Indicators for IPv6
Routing prefixes – growing bysome 6,000 prefixes per year

AS Numbers– growing by some
1,600 prefixes per year (which ishalf the V4 growth)Routing Indicators for IPv6
More Specifics now take up one
third of the routing table

The average size of a routing
advertisement is getting smaller

Routing Indicators for IPv6
Advertised Address span is
growing at a linear rate

The “shape” of inter-ASinterconnection appears to besteady, as the Average AS Path
length has been held steadythrough the yearIPv6 in 2015
• Overall IPv6 Internet growth in terms of BGP is steady atsome 6,000 route entries p.a.
This is growth of BGP route objects is 1/7 of the growth rate of theIPv4 network – as compared to the AS growth rate which is 1/2 of theIPv4 AS number growth rate

What to expect

BGP Size Projections
For the Internet this is a time of extreme uncertainty•••

Registry IPv4 address run out
Uncertainty over the impacts of any after-market in IPv4 on the routing table
Uncertainty over IPv6 takeup leads to a mixed response to IPv6 so far, and no clear
indicator of trigger points for change

V4 - Daily Growth Rates

V4 - Daily Growth Rates

V4 - Relative Daily Growth Rates

V4 - Relative Daily Growth Rates
Growth in the V4 network appears tobe constant at a long term average of120 additional routes per day, orsome 45,000 additional routes peryear
Given that the V4 address supply has
run out this implies further reductionsin address size in routes, which inturn implies ever greater reliance onNATs
Its hard to see how and why thissituation will persist at its current

IPv4 BGP Table Size predictions
Jan 2013
2014
2015
2016
2017
2018
2019
2020
2021

441,000
488,000
530,000
586,000
628,000
675,000
722,000
768,000
815,000

2014
PREDICTION

580,000
620,000
670,000
710,000
760,000

2013
PREDICTION

540,000
590,000
640,000
690,000
740,000

These numbers are dubious due to uncertainties introduced by IPv4 address
exhaustion pressures.

IPv6 Table Size

V6 - Daily Growth Rates

V6 - Relative Growth Rates

V6 - GrowthRelativeGrowth Ratesin the V6 network appears to beincreasing, but in relative terms this isslowing down.
Early adopters, who have tended to be theV4 transit providers, have already received
IPv6 allocation and are routing them. The
trailing edge of IPv6 adoption are generallycomposed of stub edge networks in IPv4.
These networks appear not to have madeany visible moves in IPv6 as yet.
If we see a change in this picture the growthtrend will likely be exponential. But its notclear when such a tipping point will occurIPv6 BGP Table Size
predictionsExponential Model

Jan 2014

Linear Model

16,100 entries

2015

21,2002016

27,0002017

38,00030,0002018

51,00035,0002019

70,00040,0002020

94,00044,0002021

127,000

49,000Range of potential outcomesBGP Table Growth• Nothing in these figures suggests that there is cause forurgent alarm -- at present• The overall eBGP growth rates for IPv4 are holding at amodest level, and the IPv6 table, although it is growing at afaster relative rate, is still small in size in absolute terms• As long as we are prepared to live within the technicalconstraints of the current routing paradigm, the Internet’s
use of BGP will continue to be viable for some time yet• Nothing is melting in terms of the size of the routing table asyet

BGP Updates• What about the level of updates in BGP?
• Let’s look at the update load from a single eBGP feed in aDFZ context

Announcements and Withdrawals

Announcements and Withdrawals

Convergence PerformanceUpdates in IPv4 BGP
Nothing in these figures is cause for any great level of concern …
– The number of updates per instability event has been relatively
constant, which for a distance vector routing protocol is weird, andcompletely unanticipated. Distance Vector routing protocols should
get noisier as the population of protocol speakers increases, and theincrease should be multiplicative.
– But this is not happening in the Internet– Which is good, but why is this not happening?
Likely contributors to this outcome are the damping effect ofwidespread use of the MRAI interval by eBGP speakers, and thetopology factor, as seen in the relatively constant V4 AS Path LengthV6 Announcements and Withdrawals

V6 Convergence Performance

V6 Updated prefixes per day

V6 Updates per eventUpdates in IPv6 BGP
IPv6 routing behaviour is diverging from IPv4 behaviour
The instability is greater
Its not the number of unstable prefixes, but the number of updates andelapsed time for the network to re-converge for each instability event
It this were to happen in the V4 network at the same relative scale it would bea major stability problem!
So what is going on and why has this happened?

Updates in IPv6
BGP Route Updates are very unequally distributed across theprefix set – they appear to affect a very small number ofprefixes which stand out well above the averageUpdates in IPv6

The busiest 48 prefixes accounted for 2/3 of all prefix updates

That’s it!