513:(CDNs) exchange Internet traffic between their networks (autonomous systems). These are often groups of local ISPs that band together to exchange data by splitting the costs of a local networking hub, avoiding the higher costs (and bandwidth charges) of a Transit AS. IXP ASNs are usually transparent. By having presence in an IXP, ASes shorten the transit path to other participating ASes, thereby reducing
169:(RIRs). The appropriate RIR then assigns ASNs to entities within its designated area from the block assigned by IANA. Entities wishing to receive an ASN must complete the application process of their RIR, LIR or upstream service provider and be approved before being assigned an ASN. Current IANA ASN assignments to RIRs can be found on the IANA website. RIRs, as part of
477:: An AS that maintains connections to more than one other AS. This allows the AS to remain connected to the Internet in the event of a complete failure of one of their connections. However, unlike a transit AS, this type of AS would not allow traffic from one AS to pass through on its way to another AS.
148:
The first and last ASNs of the original 16-bit integers (0 and 65,535) and the last ASN of the 32-bit numbers (4,294,967,295) are reserved and should not be used by operators; AS0 is used by all five RIRs to invalidate unallocated space. ASNs 64,496 to 64,511 of the original 16-bit range and 65,536
550:
AS-SETs are often used to simplify management of published routing policies. A routing policy is published in the IRR using "import" and "export" (or the newer "mp-import" and "mp-export") attributes, which each contain the source or destination AS number and the AS number imported or exported.
144:
are exactly the old 16-bit AS numbers. The special 16-bit ASN 23456 ("AS_TRANS") was assigned by IANA as a placeholder for 32-bit ASN values for the case when 32-bit-ASN capable routers ("new BGP speakers") send BGP messages to routers with older BGP software ("old BGP speakers") which do not
152:
The number of unique autonomous networks in the routing system of the
Internet exceeded 5,000 in 1999, 30,000 in late 2008, 35,000 in mid-2010, 42,000 in late 2012, 54,000 in mid-2016 and 60,000 in early 2018. The number of allocated ASNs exceeded 100,000 as of March 2021.
530:
Autonomous systems can be included in one or more AS-SETs, for example AS-SET of RIPE NCC "AS-12655" has AS1, AS2 and AS3 as its members, but AS1 is also included in other sets in ARIN (AS-INCAPSULA) and APNIC (AS-IMCL). Another AS-SET sources can be RADB, LEVEL3
104:(ISP) or a very large organization with independent connections to multiple networks, that adhered to a single and clearly defined routing policy. In March 1996, the newer definition came into use because multiple organizations can run
112:
that connects all those organizations to the
Internet. Even though there may be multiple autonomous systems supported by the ISP, the Internet only sees the routing policy of the ISP. That ISP must have an officially registered ASN.
546:
AS-SET names usually start with "AS-", but can also have a hierarchical name. For example, the administrator of AS 64500 may create an AS-SET called "AS64500:AS-UPSTREAMS", to avoid conflict with other similarly named AS-SETs.
1291:
501:: An AS that acts as a router between two ASes is called a transit. Since not all ASes are directly connected with every other AS, a transit AS carries data traffic between one AS to another AS to which it has links.
72:
prefixes under the control of one or more network operators on behalf of a single administrative entity or domain, that presents a common and clearly defined routing policy to the
Internet. Each AS is assigned an
149:
to 65,551 of the 32-bit range are reserved for use in documentation. ASNs 64,512 to 65,534 of the original 16-bit AS range, and 4,200,000,000 to 4,294,967,294 of the 32-bit range are reserved for
Private Use.
485:: An AS that is connected to only one other AS. This may be an apparent waste of an AS number if the network's routing policy is the same as its upstream AS's. However, the stub AS may have
1158:
1409:
97:(IANA). The IANA also maintains a registry of ASNs which are reserved for private use (and should therefore not be announced to the global Internet).
1261:
124:(RIRs). These numbers are written preferably as simple integers, in a notation referred to as "asplain", ranging from 0 to 4,294,967,295 (
162:
117:
94:
551:
Instead of single AS numbers, AS-SETs can be referenced in these attributes, which simplifies management of complex routing policies.
262:
839:
Validation of Route
Origination Using the Resource Certificate Public Key Infrastructure (PKI) and Route Origin Authorizations (ROAs)
1224:
811:
742:
695:
648:
610:
1499:
116:
Until 2007, AS numbers were defined as 16-bit integers, which allowed for a maximum of 65,536 assignments. Since then, the
1083:
170:
30:
1283:
468:
Autonomous systems (AS) can be grouped into four categories, depending on their connectivity and operating policy.
166:
121:
90:
86:
571:
540:
101:
65:
510:
1441:
582:
560:
505:
105:
82:
1253:
1045:
999:
941:
903:
857:
794:
756:
709:
662:
624:
490:
568:β a hotline communications system between the network operations centers of major Autonomous Systems
1479:
539:) and also ARIN has ARIN-NONAUTH source of AS-SETs. AS-SETs are created by network operators in an
174:
1257:
536:
493:. Specific examples include private interconnections in the financial and transportation sectors.
1175:
1200:
1152:
1037:
895:
1027:
989:
931:
885:
847:
784:
746:
718:
699:
671:
652:
614:
543:(IRR), like other route objects, and can be included in other AS-SETs and even form cycles.
518:
497:
268:
1107:
604:
514:
532:
1493:
1361:
815:
481:
1133:
579:β a freely available web-based database of networks that are interested in peering
606:
Guidelines for creation, selection, and registration of an
Autonomous System (AS)
1048:
1017:
1002:
983:
944:
921:
906:
875:
860:
837:
797:
774:
759:
736:
722:
712:
689:
675:
665:
642:
627:
473:
455:
438:
395:
391:
374:
357:
353:
336:
306:
276:
272:
125:
1287:
128:
0xFFFF FFFF). Or, alternatively, in the form called "asdot+" which looks like
1041:
899:
206:
100:
Originally, the definition required control by a single entity, typically an
1451:
1385:
576:
224:
958:
1469:
1313:
812:"Using AS 23456: How BGP Uses Conversion or Truncation For Compatibility"
565:
193:
1337:
1460:
Robtex: Various kinds of research of IP numbers, Domain names, ASN, etc
486:
215:
202:
93:(RIRs), which in turn receive blocks of ASNs for reassignment from the
69:
1474:
1063:
1032:
994:
936:
890:
852:
789:
751:
704:
657:
619:
220:
188:
197:
184:
1225:"Policy prop-132 (AS0 for unallocated space) deployed in service"
1084:"World - Autonomous System Number statistics - Sorted by number"
1023:
927:
881:
843:
780:
211:
1484:
985:
Autonomous System (AS) Number
Reservation for Documentation Use
1464:
776:
BGP Support for Four-Octet
Autonomous System (AS) Number Space
489:
with other autonomous systems that is not reflected in public
109:
1454:
509:(IX or IXP): A physical infrastructure through which ISPs or
1465:
astraceroute, an AS traceroute utility (part of netsniff-ng)
1459:
1432:
920:
W. Kumari; R. Bush; H. Schiller; K. Patel (August 2015).
85:(BGP) routing. Autonomous System Numbers are assigned to
1438:
738:
1254:"Understanding Autonomous Systems: Routing and Peering"
34:
1485:
Lookin'STAT Graph: number of
Autonomous systems online
1410:"Descriptions of Primary Objects - RIPE Database Docs"
89:(LIRs) and end-user organizations by their respective
1446:
235:
A complete table of available 16-bit and 32-bit ASN:
1134:"Autonomous System (AS) Number Assignment Policies"
735:Huston, Geoff; Michaelson, George (December 2008).
1019:Autonomous System (AS) Reservation for Private Use
877:Reservation of Last Autonomous System (AS) Numbers
387:Reserved for use in documentation and sample code
332:Reserved for use in documentation and sample code
1247:
1245:
180:There are other sources for more specific data:
120:has begun to also assign 32-bit AS numbers to
1201:"Revocation of Internet Resources allocation"
8:
1157:: CS1 maint: numeric names: authors list (
1062:Bates, Tony; Smith, Philip; Huston, Geoff.
603:Hawkinson, John; Bates, Tony (March 1996).
18:
836:G. Huston; G. Michaelson (February 2012).
691:BGP Support for Four-octet AS Number Space
207:https://ftp.afrinic.net/pub/stats/afrinic/
1480:Partial List of Autonomous system numbers
1284:"Glossary: Internet exchange point (IXP)"
1031:
993:
935:
889:
851:
788:
750:
703:
656:
618:
173:, can revoke AS numbers as part of their
237:
225:https://ftp.lacnic.net/pub/stats/lacnic/
140:are 16-bit numbers. Numbers of the form
24:This is an accepted version of this page
1170:
1168:
1088:Regional Internet Registries Statistics
688:Vohra, Quaizar; Chen, Enke (May 2007).
641:Rekhter, Yakov; Li, Tony (March 1995).
595:
20:
1150:
161:AS numbers are assigned in blocks by
7:
1435:β Internet Measurements and Analysis
1252:Krzyzanowski, Paul (21 March 2016).
216:https://ftp.arin.net/pub/stats/arin/
773:Q. Vohra; E. Chen (December 2012).
644:A Border Gateway Protocol 4 (BGP-4)
163:Internet Assigned Numbers Authority
95:Internet Assigned Numbers Authority
1294:from the original on 30 March 2022
1260:, Department of Computer Science.
874:J. Haas; J. Mitchell (July 2014).
189:https://ftp.apnic.net/stats/apnic/
49:
1264:from the original on 3 March 2022
1176:"Autonomous System (AS) Numbers"
1138:RIPE Network Coordination Centre
1132:Mar 2017, Publication date: 14.
302:Reserved for AS Pool Transition
198:https://ftp.ripe.net/ripe/stats/
145:understand the new 32-bit ASNs.
923:Codification of AS 0 Processing
265:unallocated space invalidation
108:using private AS numbers to an
64:) is a collection of connected
1475:CIDR and ASN assignment report
1447:Hurricane Electric BGP Toolkit
1:
814:. 2008-07-21. Archived from
167:regional Internet registries
122:regional Internet registries
91:Regional Internet Registries
982:G. Huston (December 2008).
1518:
1455:https://www.peeringdb.com/
1016:J. Mitchell (July 2013).
988:. Network Working Group.
572:Internet Routing Registry
541:Internet Routing Registry
511:content delivery networks
434:Reserved for private use
349:Reserved for private use
102:Internet service provider
87:Local Internet Registries
1386:"IDIDB - ΠΠ±ΡΠ΅ΠΊΡΡ AS-SET"
75:autonomous system number
31:latest accepted revision
1314:"AS-12655 - bgp.he.net"
963:irrexplorer.dashcare.nl
583:Routing Assets Database
561:Administrative distance
506:Internet Exchange Point
83:Border Gateway Protocol
53:Internet routing system
428:4200000000β4294967294
1500:Internet architecture
1366:irrexplorer.nlnog.net
1342:irrexplorer.nlnog.net
1108:"How to setup a LIR"
421:Public 32-bit ASNs
175:Internet governance
21:Page version status
1258:Rutgers University
537:Lumen Technologies
491:route-view servers
415:131072β4199999999
27:
461:
460:
66:Internet Protocol
58:autonomous system
1507:
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1033:10.17487/RFC6996
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1007:
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995:10.17487/RFC5398
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937:10.17487/RFC7607
917:
911:
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891:10.17487/RFC7300
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853:10.17487/RFC6483
833:
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790:10.17487/RFC6793
770:
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752:10.17487/RFC5396
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705:10.17487/RFC4893
685:
679:
669:
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658:10.17487/RFC1771
638:
632:
631:
622:
620:10.17487/RFC1930
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519:round-trip delay
238:
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1126:
1116:
1114:
1112:www.afrinic.net
1106:
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1082:
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1068:
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1056:
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1010:
981:
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967:
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919:
918:
914:
873:
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772:
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729:
687:
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613:. sec. 3.
602:
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515:network latency
466:
233:
159:
54:
47:
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45:
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12:
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5:
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1449:
1444:
1436:
1428:
1427:External links
1425:
1422:
1421:
1401:
1377:
1362:"IRR explorer"
1353:
1338:"IRR explorer"
1329:
1305:
1275:
1241:
1216:
1205:www.lacnic.net
1192:
1164:
1124:
1099:
1075:
1054:
1008:
974:
959:"IRR explorer"
950:
912:
866:
828:
803:
765:
727:
717:(obsoleted by
680:
670:(obsoleted by
633:
594:
593:
591:
588:
587:
586:
580:
574:
569:
563:
556:
553:
533:tier 1 network
527:
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517:and improving
502:
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81:), for use in
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48:
28:
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10:
9:
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2:
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1128:
1125:
1113:
1109:
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1100:
1089:
1085:
1079:
1076:
1065:
1064:"CIDR report"
1058:
1055:
1050:
1047:
1044:. BCP 6.
1043:
1039:
1034:
1029:
1025:
1021:
1020:
1012:
1009:
1004:
1001:
996:
991:
987:
986:
978:
975:
964:
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954:
951:
946:
943:
938:
933:
929:
925:
924:
916:
913:
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905:
902:. BCP 6.
901:
897:
892:
887:
883:
879:
878:
870:
867:
862:
859:
854:
849:
845:
841:
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829:
818:on 2016-10-29
817:
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440:
436:
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430:
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402:65552β131071
401:
400:
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366:
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301:
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261:Reserved for
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67:
63:
59:
51:
40:
36:
32:
25:
1413:. Retrieved
1404:
1393:. Retrieved
1390:www.ididb.ru
1389:
1380:
1369:. Retrieved
1365:
1356:
1345:. Retrieved
1341:
1332:
1321:. Retrieved
1317:
1308:
1296:. Retrieved
1278:
1266:. Retrieved
1233:. Retrieved
1231:. 2020-09-02
1228:
1219:
1208:. Retrieved
1204:
1195:
1184:. Retrieved
1182:. 2018-12-07
1179:
1141:. Retrieved
1137:
1127:
1115:. Retrieved
1111:
1102:
1091:. Retrieved
1087:
1078:
1067:. Retrieved
1057:
1018:
1011:
984:
977:
966:. Retrieved
962:
953:
922:
915:
876:
869:
838:
831:
820:. Retrieved
816:the original
806:
775:
768:
737:
730:
690:
683:
643:
636:
605:
598:
549:
545:
529:
504:
496:
480:
472:
467:
381:65536β65551
343:64512β65534
326:64496β64511
319:Public ASNs
313:23457β64495
289:Public ASNs
247:Description
234:
179:
160:
151:
147:
141:
137:
133:
129:
115:
99:
78:
74:
61:
57:
55:
50:
38:
29:This is the
23:
535:now called
445:4294967295
394:, RFC
356:, RFC
275:, RFC
177:abilities.
126:hexadecimal
39:14 May 2024
1415:2023-04-05
1395:2021-10-24
1371:2022-01-30
1347:2022-01-30
1323:2021-10-24
1318:bgp.he.net
1288:CloudFlare
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