A review of Autonomous System Numbers: what is it, how to get it, and why it’s important. It highlights the challenges of the 2-byte ASN run-out and adoption of 4-byte ASN, and how Indonesia fare compared to other economies. It then looks at the distribution of ASNs in Indonesia, and more importantly how the ASNs are interconnected locally and internationally. The presentation ends with how ASN usage may change in the future, and what role network operators can play in building a robust Internet by adopting best current practice in deploying and managing ASNs.

1. Issue Date:
Revision:
ASN distribution and
interconnection in
Indonesia
12 June 2015
1.0

2. Overview
Introduction to ASN: What is it, how to
get it, and why is it important?
2-byte and 4-byte ASN
ASNs in Indonesia: Distribution and
Interconnection
AS interconnection: It’s about cost,
resiliency and performance
Looking ahead

3. Introduction to
ASN

4. Routing the Internet
• Every Internet router needs to know the relative location of
every destination address on the Internet
• Location information is distributed across the Internet using
routing architecture
• The Internet is divided into “clouds” of interconnection
called “networks”
– Interior routing protocols (OSPF, IS-IS, etc) maintain the internal
connectedness with a network
– Exterior routing protocols (BGP) maintain a map of how each of these
networks connect to each other
– BGP uses the concept of an Autonomous System Number to
uniquely identify each component network

5. Routing and ASN
• RFC 1930:
– An AS (Autonomous System) is a connected group of one or more IP
prefixes run by one or more network operators that has a SINGLE
and CLEARLY DEFINED routing policy.
– An AS has a globally unique number (sometimes referred to as an
ASN, or Autonomous System Number) associated with it. This
number is used in both the exchange of exterior routing information
(between neighbouring AS’s), and as an identifier of the AS itself.

6. ASN distribution

7. 2-byte and 4-byte ASN
• 2-byte (16 bit ASN)
– Range: 0 – 65535
– Reserved: 0, 65535
– Documentation & Sample Code Use: 64496-64511
– Private Use: 64512 – 65534
– Public Use: 1 – 64495 (‘23456’ is used for 4-byte transition purposes)
• 4-byte (32 bit ASN)
– Range: 0 – 4294967295
– Additional Reserved: 65552 – 131071, 4294967295
– Additional Doc. & Sample Code Use: 65536 – 65551
– Additional Private Use: 4200000000 – 4294967294
– Additional Public Use: 131072 – 4199999999

8. 2-byte ASN status
199 remain at IANA (as of 8 June 2015)
http://www.potaroo.net/tools/asn16/

9. 4-byte ASN deployment
• A few issues due to
old equipment &
network operating
systems
– Better acceptance now
in all regions
• Can not be used in
BGP community
attribute
– BGP community attribute
is a 32-bit value, the
lower 16-bit specifies the
ASN
• Otherwise it WORKS JUST
FINE

10. AS
interconnection

11. The Internet
11
• Networks worldwide
interconnect to form the
Internet. They include ISPs,
Internet Exchange Points,
Universities, Corporate
networks, etc.
• Each dot represents an AS
• There are 47,000+ ASNs
currently active in the
Internet
• Networks worldwide
interconnect to form the
Internet. They include ISPs,
Internet Exchange Points,
Universities, Corporate
networks, etc.
• Each dot represents an AS
• There are 47,000+ ASNs
currently active in the
Internet
peer1.com

12. Network Interconnection
202.178.112.0/24
2400:3E00:DD::/48 202.178.112.0/24
2400:3E00:DD::/48
Multi-homed network
MAY have a need for BGP and public ASN
Single-homed network
No need for public ASN

13. Why multihome with BGP and use a
public ASN?
Good interconnection strategy can lower cost of
operation by directing traffic through the most cost
effective connections wherever possible
Good interconnection strategy can lower cost of
operation by directing traffic through the most cost
effective connections wherever possible
Understanding where your network traffic goes and
when possible shortening the path to your main
customers/suppliers/partners could result in better
overall network experience
Understanding where your network traffic goes and
when possible shortening the path to your main
customers/suppliers/partners could result in better
overall network experience
Looking further than next hop path diversification allows
you to better evaluate interconnection options, which in
turn could result in better network resiliency
Looking further than next hop path diversification allows
you to better evaluate interconnection options, which in
turn could result in better network resiliency
CostCost
PerformancePerformance
ResilienceResilience

14. Global AS Core

15. Economy level ASN transit map

16. Data source
• Routeviews.org
– RIBs from routers located in various locations (mostly Internet
Exchanges) around the world (US, Japan, Korea, UK, Australia,
Brazil, Singapore, Serbia)
• First week of April 2015 data
• RIBs collected every two hours
– This is a snapshot, not live data
• This visualisation tool is a work in progress
– APNIC values your feedback

17. Explanation
Top view Side view

18. Explanation
Top view Side view
ASNs with more
downstreams
are displayed
closer to the
centre

19. Explanation
Top view Side view
Lowest ASN shown
at the top, followed
by higher ASNs in a
clockwise direction

20. Explanation
Top view Side view
Darker nodes/path
means there are more IP
addresses involved in
that route

21. Explanation
Top view Side view
Maximum observed path length

22. Singapore

23. Malaysia

24. Philippines

25. Thailand

26. Indonesia
530 advertised ASNs

27. 4-byte ASN in Indonesia
4-byte range

28. 4-byte ASN in Indonesia

29. 4-byte ASN in Indonesia

30. Measurements by the Atlas project
RIPE Atlas employs a global
network of probes that
measure Internet
connectivity and
reachability, providing an
unprecedented
understanding of the state of
the Internet in real time
https://atlas.ripe.net/
Need more probes
in Indonesia

31. Domestic/International path

32. Domestic/International path
AS4796
AS59785

33. Domestic/International path
AS4796
AS38158

34. Transit & peering view
• Visibility of private peerings, which can not be seen on the
global routing table

35. Need your help
• More Atlas probes on different ASNs, cities, transit paths,
exchanges, etc.

36. Looking ahead
• As more organisations interconnect with upstreams,
downstreams and peers, the number of advertised ASNs
will continue to grow
• Opportunities to reduce cost, improve resiliency and
performance will be available to those with awareness of
this rich network ecosystem
• New technologies such as SDN and network virtualisation
will drive innovations and change the way networks are
interconnected, so expect to see a more dynamic
ecosystem in the future

37. Things to consider if you operate an
ASN
Routing Security
Registration
Aggregation

38. Routing security
• As more networks interconnect, security and stability risks
such as route hijacking, accidental route leakage and other
issues can escalate
• Register and maintain your ‘route’ and ‘route6’ objects in
the APNIC Whois database
– Ensure the import and export attributes accurately reflect your actual
routing policy
• Create your ROA
– A ROA or Route Origin Authorization is an attestation of a BGP route
announcement. It attests that the origin AS number is authorized to
announce the prefix(es). The attestation can be verified
cryptographically using RPKI

39. ROA
• Create your ROA now in MyAPNIC (or ask IDNIC)
• Benefits
– Verify whether an AS is authorized to announce a specific IP prefix
– Minimize common routing errors
– Prevent most accidental hijacks
• What's contained in a ROA
– The AS number you authorize
– The prefix that is being originated from it
– The most specific prefix (maximum length) that the AS may announce
• Example of what a ROA says in plain language:
– "ISP 4 permits AS 65000 to originate a route for the prefix
192.2.200.0/24"
http://www.apnic.net/roa

40. Registration
• With IPv4 address space nearing exhaustion and transfers
taking place, it’s really important that everyone keeps the
resource registry updated
• Protect your Internet resource registration information
– Keep your APNIC Whois data up to date
• IPv4 range (inetnum)
• IPv6 range (inet6num)
• ASN (autnum)
• Admin contact (admin-c)
• Technical contact (tech-c)
• Incident Response Team contact (irt)
• Help everyone resolve operational issues quickly
– Report invalid contacts

41. Aggregation
• As more routing information entries get added to the global
routing table, it’s important that prefix announcements are
aggregated whenever possible
• The algorithm used in the report (see next slide) proposes
aggregation only when there is a precise match using AS
path so as to preserve traffic transit policies. Aggregation is
also proposed across non-advertised address space
('holes').
http://www.cidr-report.org

43. 43