217:, placing each data packet into one of a limited number of traffic classes. Each router on the network is then configured to differentiate traffic based on its class. Each traffic class can be managed differently, ensuring preferential treatment for higher-priority traffic on the network. The premise of Diffserv is that complicated functions such as packet classification and policing can be carried out at the edge of the network by edge routers. Since no classification and policing is required in the core routers, functionality there can then be kept simple. Core routers simply apply PHB treatment to packets based on their markings. PHB treatment is achieved by core routers using a combination of scheduling policy and queue management policy.
237:
classifiers may honor any DiffServ markings in received packets or may elect to ignore or override those markings. For tight control over volumes and type of traffic in a given class, a network operator may choose not to honor markings at the ingress to the DiffServ domain. Traffic in each class may be further conditioned by subjecting the traffic to
1113:(SLA). By marking the packets, the sender indicates that it wants the packets to be treated as a specific service, but there is no guarantee this happens. It is up to all the service providers and their routers in the path to ensure that their policies will take care of the packets in an appropriate fashion.
1108:
The details of how individual routers deal with the DS field are configuration specific, therefore it is difficult to predict end-to-end behavior. This is complicated further if a packet crosses two or more DiffServ domains before reaching its destination. From a commercial viewpoint, this means that
746:
The Class
Selector code points are of the binary form 'xxx000'. The first three bits are the IP precedence bits. Each IP precedence value can be mapped into a DiffServ class. IP precedence 0 maps to CS0, IP precedence 1 to CS1, and so on. If a packet is received from a non-DiffServ-aware router that
259:
In theory, a network could have up to 64 different traffic classes using the 64 available DSCP values. The DiffServ RFCs recommend, but do not require, certain encodings. This gives a network operator great flexibility in defining traffic classes. In practice, however, most networks use the following
1125:
in the framework of DiffServ is an agent that has some knowledge of an organization's priorities and policies and allocates bandwidth with respect to those policies. In order to achieve an end-to-end allocation of resources across separate domains, the
Bandwidth Broker managing a domain will have to
236:
Network traffic entering a DiffServ domain is subjected to classification and conditioning. A traffic classifier may inspect many different parameters in incoming packets, such as source address, destination address or traffic type and assign individual packets to a specific traffic class. Traffic
738:
byte of the IPv4 header to mark priority traffic. The TOS octet and IP precedence were not widely used. The IETF agreed to reuse the TOS octet as the DS field for DiffServ networks, later splitting it into the DS field and ECN field. In order to maintain backward compatibility with network devices
227:
While DiffServ does recommend a standardized set of traffic classes, the DiffServ architecture does not incorporate predetermined judgments of what types of traffic should be given priority treatment. DiffServ simply provides a framework to allow classification and differentiated treatment. The
102:
Modern data networks carry many different types of services, including voice, video, streaming music, web pages and email. Many of the proposed QoS mechanisms that allowed these services to co-exist were both complex and failed to scale to meet the demands of the
294:
A default forwarding (DF) PHB is the only required behavior. Essentially, any traffic that does not meet the requirements of any of the other defined classes uses DF. Typically, DF has best-effort forwarding characteristics. The recommended DSCP for DF is 0.
1100:
Under DiffServ, all the policing and classifying are done at the boundaries between DiffServ domains. This means that in the core of the
Internet, routers are unhindered by the complexities of collecting payment or enforcing agreements. That is, in contrast to
383:. Assured forwarding allows the operator to provide assurance of delivery as long as the traffic does not exceed some subscribed rate. Traffic that exceeds the subscription rate faces a higher probability of being dropped if congestion occurs.
1109:
it is impossible to sell different classes of end-to-end connectivity to end users, as one provider's Gold packet may be another's Bronze. DiffServ or any other IP-based QoS marking does not ensure the quality of the service or a specified
386:
The AF behavior group defines four separate AF classes with all traffic within one class having the same priority. Within each class, packets are given a drop precedence (high, medium or low, where higher precedence means
311:. The EF PHB has the characteristics of low delay, low loss and low jitter. These characteristics are suitable for voice, video and other realtime services. EF traffic is often given
315:
above all other traffic classes. Because an overload of EF traffic will cause queuing delays and affect the jitter and delay tolerances within the class,
347:. The Voice Admit PHB has identical characteristics to the Expedited Forwarding PHB. However, Voice Admit traffic is also admitted by the network using a
475:
classes, the traffic in the higher class is given priority. Rather than using strict priority queuing, more balanced queue servicing algorithms such as
570:
20:
202:(PHBs), which define the packet-forwarding properties associated with a class of traffic. Different PHBs may be defined to offer, for example,
1150:. Note that the DS field of 8 bits (the bottom two unused) in was later split into the current 6-bit DS field and a separate 2-bit ECN field.
1867:
228:
standard traffic classes (discussed below) serve to simplify interoperability between different networks and different vendors' equipment.
1914:
1890:
391:
dropping). The combination of classes and drop precedence yields twelve separate DSCP encodings from AF11 through AF43 (see table).
320:
242:
213:
Rather than differentiating network traffic based on the requirements of an individual flow, DiffServ operates on the principle of
253:
1804:
1738:
1941:
1126:
communicate with its adjacent peers, which allows end-to-end services to be constructed out of purely bilateral agreements.
471:
Some measure of priority and proportional fairness is defined between traffic in different classes. Should congestion occur
1926:
1781:
252:
The per-hop behavior is determined by the DS and ECN fields in the IP header. The DS field contains the 6-bit DSCP value.
1920:
90:) in the IP header for packet classification purposes. The DS field, together with the ECN field, replaces the outdated
1951:
1946:
677:
1618:
A DiffServ domain is composed of a group of interconnected DiffServ nodes that use the same service policy and PHBs.
747:
used IP precedence markings, the DiffServ router can still understand the encoding as a Class
Selector code point.
146:
In the DS field, a range of eight values (class selectors) is used for backward compatibility with the former IPv4
1105:, DiffServ requires no advance setup, no reservation, and no time-consuming end-to-end negotiation for each flow.
593:
765:
offers detailed and specific recommendations for the use and configuration of code points. Other RFCs such as
1686:
1636:
1470:
1392:
1110:
487:
a class, the packets with the higher drop precedence are discarded first. To prevent issues associated with
312:
492:
348:
220:
A group of routers that implement common, administratively defined DiffServ policies are referred to as a
214:
1236:— Supplemental information for the new definition of the EF PHB (expedited forwarding per-hop behavior).
480:
1837:
1760:
1706:
1656:
1600:
1551:
1490:
1429:
561:
256:(ECN) occupies the least-significant 2 bits of the IPv4 TOS field and IPv6 traffic class (TC) field.
19:
This article is about communication networks. For the design pattern for business applications, see
159:
60:
39:
architecture that specifies a mechanism for classifying and managing network traffic and providing
36:
632:
163:
40:
1190:— Definition of differentiated services per-domain behaviors and rules for their specification.
1886:
1863:
1752:
316:
44:
1827:
1742:
1696:
1646:
1541:
1480:
1419:
1387:
1370:
1360:
1350:
1333:
1325:
1317:
1309:
1299:
1291:
1283:
1273:
1263:
1255:
1247:
1239:
1229:
1219:
1211:
1201:
1193:
1183:
1173:
1163:
1153:
1135:
1122:
778:
766:
758:
376:
368:
340:
304:
199:
1808:
735:
637:
246:
151:
104:
91:
56:
323:
and other mechanisms may be applied to EF traffic. The recommended DSCP for EF is 101110
1921:
Modeling and
Understanding End-to-End Class of Service Policies in Operational Networks
1476:
Definition of the
Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers
1290:— A differentiated services code point (DSCP) for capacity-admitted traffic. (Updates
750:
Specific recommendations for use of Class
Selector code points are given in RFC 4594.
1935:
1879:
1801:
731:
518:
238:
207:
68:
52:
48:
1907:
476:
1316:— A Lower-Effort Per-Hop Behavior (LE PHB) for Differentiated Services. (Updates
1840:
1821:
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198:
packets as belonging to a specific class. DiffServ-aware routers implement
1357:— Management information base for the differentiated services architecture.
285:
PHBs — which maintain backward compatibility with the IP precedence field.
1860:
Deploying IP and MPLS QoS for
Multiservice Networks: Theory and Practice
1102:
155:
1832:
1747:
1701:
1651:
1606:
1546:
1485:
1424:
1377:— Differentiated services quality of service policy information base.
601:
597:
1142:— Definition of the differentiated services field (DS field) in the
1731:
G. Tsirtsis; G. Giaretta; H. Soliman; N. Montavont (January 2011).
1367:— An informal management model for differentiated services routers.
685:
681:
279:(AF) PHB — gives assurance of delivery under prescribed conditions
127:, which was later split to refer to only the top 6 bits with the
1143:
623:
585:
108:
1823:
351:(CAC) procedure. The recommended DSCP for voice admit is 101100
589:
557:
1923:: proposes a practical model for extracting DiffServ policies
1537:
The
Addition of Explicit Congestion Notification (ECN) to IP
1246:— New Terminology and Clarifications for Diffserv. (Updates
182:
mechanism for traffic management. In contrast, IntServ is a
739:
that still use the Precedence field, DiffServ defines the
1927:
Cisco: Implementing Quality of Service Policies with DSCP
1915:
DiffServ-The Scalable End-to-End Quality of Service Model
985:
Using single-rate, three-color marker (such as RFC 2697)
367:
The IETF defines the Assured Forwarding (AF) behavior in
1280:— Configuration Guidelines for DiffServ Service Classes.
47:
networks. DiffServ can, for example, be used to provide
491:, more sophisticated drop selection algorithms such as
303:
The IETF defines Expedited Forwarding (EF) behavior in
1534:
K. Ramakrishnan; S. Floyd; D. Black (September 2001).
1031:
Using two-rate, three-color marker (such as RFC 2698)
939:
Using two-rate, three-color marker (such as RFC 2698)
893:
Using two-rate, three-color marker (such as RFC 2698)
1642:
Configuration Guidelines for DiffServ Service Classes
273:(EF) PHB — dedicated to low-loss, low-latency traffic
143:
field where it occupies the 6 most significant bits.
1782:"Implementing Quality of Service Policies with DSCP"
1200:— Per hop behavior identification codes. (Obsoletes
1602:
S3700HI Ethernet Switches Configuration Guide - QoS
1878:
267:(DF) PHB — which is typically best-effort traffic
16:Networking architecture for prioritizing traffic
1820:K. Nichols; V. Jacobson; L. Zhang (July 1999).
1415:New Terminology and Clarifications for DiffServ
730:Prior to DiffServ, IPv4 networks could use the
1160:— An architecture for differentiated services.
150:field. Today, DiffServ has largely supplanted
1092:sr+bs = single rate with burst size control.
190:mechanism. DiffServ relies on a mechanism to
8:
483:are likely to be used. If congestion occurs
1218:— An expedited forwarding PHB. (Obsoletes
1831:
1746:
1700:
1650:
1630:
1628:
1626:
1545:
1529:
1527:
1484:
1464:
1462:
1460:
1458:
1423:
705:Routing protocols (OSPF, BGP, ISIS, RIP)
571:operations, administration and management
339:The IETF defines Voice Admit behavior in
1881:Differentiated services for the Internet
775:
659:Gaming, low priority video conferencing
629:streaming of live audio and video events
502:
393:
1689:; W. Weiss; J. Wroclawski (June 1999).
1404:
162:(IntServ), as the primary architecture
21:Differentiated service (design pattern)
1858:John Evans; Clarence Filsfils (2007).
1180:— Differentiated services and tunnels.
7:
773:have updated these recommendations.
260:commonly defined per-hop behaviors:
51:to critical network traffic such as
1734:Traffic Selectors for Flow Bindings
1885:. Macmillan Technical Publishing.
395:Assured Forwarding behavior group
76:differentiated services code point
14:
63:to non-critical services such as
254:Explicit Congestion Notification
1739:Internet Engineering Task Force
1170:— Assured forwarding PHB group.
131:in the bottom two bits. In the
1:
170:Traffic management mechanisms
84:differentiated services field
1692:Assured Forwarding PHB Group
1473:; D. Black (December 1998).
1968:
1721:.
1675:.
1590:.
1521:.
1452:.
1412:D. Grossman (April 2002).
232:Classification and marking
18:
1695:. Network Working Group.
1645:. Network Working Group.
1540:. Network Working Group.
1479:. Network Working Group.
1345:DiffServ Management RFCs
884:Multimedia conferencing
799:Conditioning at DS edge
754:Configuration guidelines
710:Reserved for future use
523:Examples of application
158:QoS mechanisms, such as
107:. In December 1998, the
1393:Teletraffic engineering
1111:service-level agreement
727:DF= Default Forwarding
504:Class Selector mapping
313:strict priority queuing
29:Differentiated services
1908:DiffServ Working Group
1877:Kalevi Kilkki (1999).
1807:July 29, 2016, at the
1578:. Updated by RFC
1509:. Updated by RFC
1469:K. Nichols; S. Blake;
907:Real-time interactive
647:Real-time interactive
493:random early detection
465:AF43 (DSCP 38) 100110
448:AF42 (DSCP 36) 100100
431:AF41 (DSCP 34) 100010
349:Call Admission Control
215:traffic classification
74:DiffServ uses a 6-bit
1942:Internet architecture
1919:ACM SIGCOMM'09 paper-
1635:J. Babiarz; K. Chan;
1096:Design considerations
1022:High-throughput data
930:Multimedia streaming
481:weighted fair queuing
462:AF33 (DSCP 30) 011110
459:AF23 (DSCP 22) 010110
456:AF13 (DSCP 14) 001110
445:AF32 (DSCP 28) 011100
442:AF22 (DSCP 20) 010100
439:AF12 (DSCP 12) 001100
428:AF31 (DSCP 26) 011010
425:AF21 (DSCP 18) 010010
422:AF11 (DSCP 10) 001010
1717:Updated by RFC
1667:Updated by RFC
299:Expedited Forwarding
271:Expedited Forwarding
166:use to provide QoS.
1913:Cisco Whitepaper —
1862:. Morgan Kaufmann.
1566:. Updates RFC
1562:Obsoletes RFC
1501:Obsoletes RFC
916:Police using sr+bs
786:
505:
396:
160:integrated services
61:best-effort service
37:computer networking
1952:Quality of service
1947:Internet Standards
1769:Proposed Standard.
1715:Proposed Standard.
1560:Proposed Standard.
1499:Proposed Standard.
1008:Police using sr+bs
962:Police using sr+bs
870:Police using sr+bs
847:Police using sr+bs
776:
633:video surveillance
544:Low-priority data
503:
394:
363:Assured Forwarding
290:Default Forwarding
277:Assured Forwarding
265:Default Forwarding
41:quality of service
1869:978-0-12-370549-5
1440:Updates RFC
1090:
1089:
1025:AF11, AF12, AF13
979:AF21, AF22, AF23
976:Low-latency data
933:AF31, AF32, AF33
887:AF41, AF42, AF43
725:
724:
469:
468:
317:admission control
200:per-hop behaviors
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1833:10.17487/RFC2638
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1409:
1388:Class of service
1123:Bandwidth Broker
1117:Bandwidth broker
787:
785:recommendations
693:Network control
608:Broadcast video
506:
495:are often used.
397:
321:traffic policing
243:traffic policers
59:while providing
43:(QoS) on modern
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1639:(August 2006).
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1077:Not applicable
953:Broadcast video
823:See section 3.1
813:Network control
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638:video-on-demand
556:File transfer (
501:
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222:DiffServ domain
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139:is part of the
105:public Internet
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82:) in the 6-bit
57:streaming media
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1802:Filtering DSCP
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1665:Informational.
1655:. STD 67.
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1438:Informational.
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1054:Not applicable
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176:coarse-grained
174:DiffServ is a
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119:fields in the
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69:file transfers
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1685:J. Heinanen;
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1362:
1359:
1356:
1352:
1349:
1348:
1344:
1339:
1335:
1331:
1327:
1323:
1319:
1315:
1311:
1308:
1305:
1301:
1297:
1293:
1289:
1285:
1282:
1279:
1275:
1272:
1269:
1265:
1261:
1257:
1253:
1249:
1245:
1241:
1238:
1235:
1231:
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1225:
1221:
1217:
1213:
1210:
1207:
1203:
1199:
1195:
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1189:
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1179:
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1169:
1165:
1162:
1159:
1155:
1152:
1149:
1145:
1141:
1137:
1134:
1133:
1130:DiffServ RFCs
1129:
1127:
1124:
1116:
1114:
1112:
1106:
1104:
1095:
1093:
1085:
1082:
1079:
1076:
1073:
1070:
1068:Lower-effort
1067:
1066:
1062:
1059:
1056:
1053:
1050:
1047:
1044:
1043:
1040:Yes per DSCP
1039:
1036:
1033:
1030:
1027:
1024:
1021:
1020:
1016:
1013:
1010:
1007:
1004:
1001:
998:
997:
994:Yes per DSCP
993:
990:
987:
984:
981:
978:
975:
974:
970:
967:
964:
961:
958:
955:
952:
951:
948:Yes per DSCP
947:
944:
941:
938:
935:
932:
929:
928:
924:
921:
918:
915:
912:
909:
906:
905:
902:Yes per DSCP
901:
898:
895:
892:
889:
886:
883:
882:
878:
875:
872:
869:
866:
863:
860:
859:
855:
852:
849:
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843:
840:
837:
836:
832:
829:
826:
824:
821:
818:
815:
812:
811:
807:
804:
801:
798:
795:
792:
789:
788:
784:
780:
774:
772:
768:
764:
760:
753:
751:
748:
744:
742:
737:
734:field in the
733:
732:IP precedence
728:
721:
718:
715:
712:
709:
708:
704:
701:
698:
695:
692:
691:
687:
683:
679:
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533:
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519:IP precedence
517:
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511:
508:
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478:
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464:
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278:
275:
272:
269:
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261:
257:
255:
250:
248:
244:
240:
239:rate limiters
231:
229:
225:
223:
218:
216:
211:
209:
205:
201:
197:
193:
189:
185:
181:
177:
169:
167:
165:
161:
157:
153:
149:
148:IP precedence
144:
142:
141:Traffic Class
138:
134:
130:
126:
122:
118:
117:IP precedence
114:
111:replaced the
110:
106:
97:
95:
93:
89:
85:
81:
77:
72:
70:
66:
62:
58:
54:
50:
46:
42:
38:
34:
30:
26:
22:
1880:
1859:
1822:
1815:
1797:
1786:. Retrieved
1775:
1768:
1733:
1726:
1714:
1691:
1680:
1664:
1641:
1617:
1611:, retrieved
1601:
1595:
1559:
1536:
1498:
1475:
1437:
1414:
1407:
1332:, obsoletes
1148:IPv6 headers
1120:
1107:
1099:
1091:
757:
749:
745:
740:
729:
726:
626:broadcast TV
484:
477:fair queuing
472:
470:
402:probability
388:
385:
366:
338:
302:
293:
282:
276:
270:
264:
258:
251:
235:
226:
221:
219:
212:
195:
191:
187:
184:fine-grained
183:
179:
175:
173:
147:
145:
140:
136:
128:
124:
116:
112:
101:
87:
83:
79:
75:
73:
32:
28:
27:
25:
1780:Worldwide.
1609:, p. 7
1028:10, 12, 14
982:18, 20, 22
936:26, 28, 30
890:34, 36, 38
796:DSCP Value
515:DSCP Value
335:Voice Admit
208:low-latency
180:class-based
133:IPv6 header
121:IPv4 header
65:web traffic
49:low-latency
1936:Categories
1788:2010-10-16
1613:2016-10-07
1399:References
793:DSCP Name
664:Signaling
512:DSCP Name
188:flow-based
154:and other
98:Background
1757:2070-1721
1083:Priority
1080:RFC 8622
1034:RFC 2597
988:RFC 2597
942:RFC 2597
919:RFC 2474
896:RFC 2597
861:Signaling
838:Telephony
531:CS0 (DF)
528:Standard
489:tail drop
355:(44 or 2C
327:(46 or 2E
210:service.
129:ECN field
123:with the
1826:. IETF.
1805:Archived
1741:(IETF).
1687:F. Baker
1637:F. Baker
1471:F. Baker
1382:See also
1057:RFC 2474
1045:Standard
1011:RFC 2474
965:RFC 2474
873:RFC 2474
853:Priority
850:RFC 3246
827:RFC 2474
805:Queuing
719:7 (111)
702:6 (110)
673:5 (101)
656:4 (100)
617:3 (011)
582:2 (010)
569:Network
553:1 (001)
537:0 (000)
414:Class 4
204:low-loss
192:classify
137:DS field
125:DS field
92:IPv4 TOS
88:DS field
33:DiffServ
1784:. Cisco
1103:IntServ
688:), NTP
473:between
436:Medium
411:Class 3
408:Class 2
405:Class 1
247:shapers
164:routers
156:layer-3
94:field.
1889:
1866:
1755:
1607:Huawei
1373:
1363:
1353:
1336:
1328:
1320:
1312:
1302:
1294:
1286:
1276:
1266:
1258:
1250:
1242:
1232:
1222:
1214:
1204:
1196:
1186:
1176:
1166:
1156:
1138:
781:
769:
761:
602:syslog
598:Telnet
573:(OAM)
485:within
379:
371:
343:
307:
1906:IETF
1037:Rate
991:Rate
945:Rate
922:Rate
899:Rate
777:IETF
743:PHB.
686:H.248
682:H.323
453:High
53:voice
35:is a
1910:page
1887:ISBN
1864:ISBN
1841:2638
1764:6088
1753:ISSN
1719:3260
1710:2597
1673:8622
1671:and
1669:5865
1660:4594
1588:8311
1586:and
1584:6040
1580:4301
1574:and
1572:2401
1568:2474
1564:2481
1555:3168
1519:8436
1517:and
1515:3260
1511:3168
1507:1349
1505:and
1503:1455
1494:2474
1450:2597
1448:and
1446:2475
1442:2474
1433:3260
1375:3317
1365:3290
1355:3289
1338:3662
1330:8325
1324:and
1322:4594
1314:8622
1304:4594
1298:and
1296:4542
1288:5865
1278:4594
1268:2597
1262:and
1260:2475
1252:2474
1244:3260
1234:3247
1224:2598
1216:3246
1206:2836
1198:3140
1188:3086
1178:2983
1168:2597
1158:2475
1146:and
1144:IPv4
1140:2474
1086:Yes
1063:Yes
1060:Rate
1017:Yes
1014:Rate
1002:CS2
968:Rate
956:CS3
910:CS4
876:Rate
864:CS5
833:Yes
830:Rate
816:CS6
808:AQM
802:PHB
783:4594
771:8622
763:4594
713:CS7
696:CS6
667:CS5
650:CS4
624:RTSP
611:CS3
594:Ping
586:SNMP
576:CS2
547:CS1
419:Low
400:Drop
389:more
381:3260
375:and
373:2597
345:5865
309:3246
196:mark
194:and
135:the
115:and
109:IETF
80:DSCP
1838:RFC
1828:doi
1761:RFC
1743:doi
1707:RFC
1697:doi
1657:RFC
1647:doi
1576:793
1552:RFC
1542:doi
1491:RFC
1481:doi
1430:RFC
1420:doi
1371:RFC
1361:RFC
1351:RFC
1334:RFC
1326:RFC
1318:RFC
1310:RFC
1300:RFC
1292:RFC
1284:RFC
1274:RFC
1264:RFC
1256:RFC
1248:RFC
1240:RFC
1230:RFC
1220:RFC
1212:RFC
1202:RFC
1194:RFC
1184:RFC
1174:RFC
1164:RFC
1154:RFC
1136:RFC
1071:LE
1048:DF
999:OAM
971:No
925:No
913:32
879:No
856:No
841:EF
779:RFC
767:RFC
759:RFC
736:TOS
716:56
699:48
678:SIP
670:40
653:32
614:24
590:SSH
579:16
562:SMB
558:FTP
479:or
377:RFC
369:RFC
359:).
341:RFC
331:).
305:RFC
245:or
206:or
152:TOS
113:TOS
67:or
55:or
31:or
1938::
1836:.
1759:.
1751:.
1737:.
1705:.
1625:^
1616:,
1605:,
1582:,
1570:,
1550:.
1526:^
1513:,
1489:.
1457:^
1444:,
1428:.
1418:.
1340:.)
1306:.)
1270:.)
1254:,
1226:.)
1121:A
1074:1
1005:16
959:24
867:40
844:46
819:48
684:,
680:,
600:,
596:,
592:,
588:,
564:)
560:,
550:8
534:0
319:,
249:.
241:,
224:.
186:,
178:,
71:.
45:IP
1895:.
1872:.
1843:.
1830::
1791:.
1766:.
1745::
1712:.
1699::
1662:.
1649::
1557:.
1544::
1496:.
1483::
1435:.
1422::
1208:.
1051:0
357:H
353:B
329:H
325:B
86:(
78:(
23:.
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