File: rfc2647.txt

package info (click to toggle)
doc-rfc 20181229-2
  • links: PTS, VCS
  • area: non-free
  • in suites: buster
  • size: 570,944 kB
  • sloc: xml: 285,646; sh: 107; python: 90; perl: 42; makefile: 14
file content (1459 lines) | stat: -rw-r--r-- 45,374 bytes parent folder | download | duplicates (5)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459






Network Working Group                                       D. Newman
Request for Comments: 2647                        Data Communications
Category: Informational                                   August 1999


           Benchmarking Terminology for Firewall Performance

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1999).  All Rights Reserved.

Table of Contents

   1. Introduction...................................................2
   2. Existing definitions...........................................2
   3. Term definitions...............................................3
   3.1 Allowed traffic...............................................3
   3.2 Application proxy.............................................3
   3.3 Authentication................................................4
   3.4 Bit forwarding rate...........................................5
   3.5 Circuit proxy.................................................6
   3.6 Concurrent connections........................................6
   3.7 Connection....................................................7
   3.8 Connection establishment......................................9
   3.9 Connection establishment time.................................9
   3.10 Connection maintenance......................................10
   3.11 Conection overhead..........................................11
   3.12 Connection teardown.........................................11
   3.13 Connection teardown time....................................12
   3.14 Data source.................................................12
   3.15 Demilitarized zone..........................................13
   3.16 Firewall....................................................13
   3.17 Goodput.....................................................14
   3.18 Homed.......................................................15
   3.19 Illegal traffic.............................................15
   3.20 Logging.....................................................16
   3.21 Network address translation.................................16
   3.22 Packet filtering............................................17
   3.23 Policy......................................................17
   3.24 Protected network...........................................18
   3.25 Proxy.......................................................19
   3.26 Rejected traffic............................................19



Newman                       Informational                      [Page 1]

RFC 2647            Firewall Performance Terminology         August 1999


   3.27 Rule set....................................................20
   3.28 Security association........................................20
   3.29 Stateful packet filtering...................................21
   3.30 Tri-homed...................................................22
   3.31 Unit of transfer............................................22
   3.32 Unprotected network.........................................23
   3.33 User........................................................23
   4. Security considerations.......................................24
   5. References....................................................25
   6. Acknowledgments...............................................25
   7. Contact Information...........................................25
   8. Full Copyright Statement......................................26

1. Introduction

   This document defines terms used in measuring the performance of
   firewalls. It extends the terminology already used for benchmarking
   routers and switches with definitions specific to firewalls.

   Forwarding rate and connection-oriented measurements are the primary
   metrics used in this document.

   Why do we need firewall performance measurements? First, despite the
   rapid rise in firewall deployment, there is no standard method of
   performance measurement. Second, implementations vary widely, making
   it difficult to do direct performance comparisons. Finally, more and
   more organizations are deploying firewalls on internal networks
   operating at relatively high speeds, while most firewall
   implementations remain optimized for use over relatively low-speed
   wide-area connections. As a result, users are often unsure whether
   the products they buy will stand up to relatively heavy loads.

2. Existing definitions

   This document uses the conceptual framework established in RFCs 1242
   and 2544 (for routers) and RFC 2285 (for switches). The router and
   switch documents contain discussions of several terms relevant to
   benchmarking the performance of firewalls. Readers should consult the
   router and switch documents before making use of this document.

   This document uses the definition format described in RFC 1242,
   Section 2. The sections in each definition are: definition,
   discussion, measurement units (optional), issues (optional), and
   cross-references.







Newman                       Informational                      [Page 2]

RFC 2647            Firewall Performance Terminology         August 1999


3. Term definitions

3.1 Allowed traffic

   Definition:
     Packets forwarded as a result of the rule set of the device under
     test/system under test (DUT/SUT).

   Discussion:
     Firewalls typically are configured to forward only those packets
     explicitly permitted in the rule set. Forwarded packets must be
     included in calculating the bit forwarding rate or maximum bit
     forwarding rate of the DUT/SUT. All other packets must not be
     included in bit forwarding rate calculations.

     This document assumes 1:1 correspondence of allowed traffic offered
     to the DUT/SUT and forwarded by the DUT/SUT. There are cases where
     the DUT/SUT may forward more traffic than it is offered; for
     example, the DUT/SUT may act as a mail exploder or a multicast
     server. Any attempt to benchmark forwarding rates of such traffic
     must include a description of how much traffic the tester expects
     to be forwarded.

   Unit of measurement:
     not applicable

   Issues:

   See also:
     policy
     rule set

3.2 Application proxy

   Definition:
     A proxy service that is set up and torn down in response to a
     client request, rather than existing on a static basis.

   Discussion:
     Circuit proxies always forward packets containing a given port
     number if that port number is permitted by the rule set.
     Application proxies, in contrast, forward packets only once a
     connection has been established using some known protocol. When the
     connection closes, a firewall using applicaton proxies rejects
     individual packets, even if they contain port numbers allowed by a
     rule set.





Newman                       Informational                      [Page 3]

RFC 2647            Firewall Performance Terminology         August 1999


   Unit of measurement:
     not applicable

   Issues:
     circuit proxy
     rule sets

   See also:
     allowed traffic
     circuit proxy
     proxy
     rejected traffic
     rule set

3.3 Authentication

   Definition:
     The process of verifying that a user requesting a network resource
     is who he, she, or it claims to be, and vice versa.

   Discussion:
     Trust is a critical concept in network security. Any network
     resource (such as a file server or printer) typically requires
     authentication before granting access.

     Authentication takes many forms, including but not limited to IP
     addresses; TCP or UDP port numbers; passwords; external token
     authentication cards; and biometric identification such as
     signature, speech, or retina recognition systems.

     The entity being authenticated might be the client machine (for
     example, by proving that a given IP source address really is that
     address, and not a rogue machine spoofing that address) or a user
     (by proving that the user really is who he, she, or it claims to
     be).  Servers might also authenticate themselves to clients.

     Testers should be aware that in an increasingly mobile society,
     authentication based on machine-specific criteria such as an IP
     address or port number is not equivalent to verifying that a given
     individual is making an access request. At this writing systems
     that verify the identity of users are typically external to the
     firewall, and may introduce additional latency to the overall SUT.

   Unit of measurement:
     not applicable

   Issues:




Newman                       Informational                      [Page 4]

RFC 2647            Firewall Performance Terminology         August 1999


   See also:
     user

3.4 Bit forwarding rate

   Definition:
     The number of bits per second of allowed traffic a DUT/SUT can be
     observed to transmit to the correct destination interface(s) in
     response to a specified offered load.

   Discussion:
     This definition differs substantially from section 3.17 of RFC 1242
     and section 3.6.1 of RFC 2285.

     Unlike both RFCs 1242 and 2285, this definition introduces the
     notion of different classes of traffic: allowed, illegal, and
     rejected (see definitions for each term). For benchmarking
     purposes, it is assumed that bit forwarding rate measurements
     include only allowed traffic.

     Unlike RFC 1242, there is no reference to lost or retransmitted
     data.  Forwarding rate is assumed to be a goodput measurement, in
     that only data successfully forwarded to the destination interface
     is measured.  Bit forwarding rate must be measured in relation to
     the offered load.  Bit forwarding rate may be measured with
     differed load levels, traffic orientation, and traffic
     distribution.

     Unlike RFC 2285, this measurement counts bits per second rather
     than frames per second. Testers interested in frame (or frame-like)
     measurements should use units of transfer.

   Unit of measurement:
     bits per second

   Issues:
     Allowed traffic vs. rejected traffic

   See also:
     allowed traffic
     goodput
     illegal traffic
     rejected traffic
     unit of transfer







Newman                       Informational                      [Page 5]

RFC 2647            Firewall Performance Terminology         August 1999


3.5 Circuit proxy

   Definition:
     A proxy service that statically defines which traffic will be
     forwarded.

   Discussion:
     The key difference between application and circuit proxies is that
     the latter are static and thus will always set up a connection if
     the DUT/SUT's rule set allows it. For example, if a firewall's rule
     set permits ftp connections, a circuit proxy will always forward
     traffic on TCP port 20 (ftp-data) even if no control connection was
     first established on TCP port 21 (ftp-control).

   Unit of measurement:
     not applicable

   Issues:
     application proxy
     rule sets

   See also:
     allowed traffic
     application proxy
     proxy
     rejected traffic
     rule set

3.6 Concurrent connections

   Definition:
     The aggregate number of simultaneous connections between hosts
     across the DUT/SUT, or between hosts and the DUT/SUT.

   Discussion:
     The number of concurrent connections a firewall can support is just
     as important a metric for some users as maximum bit forwarding
     rate.

     While "connection" describes only a state and not necessarily the
     transfer of data, concurrency assumes that all existing connections
     are in fact capable of transferring data. If a data cannot be sent
     over a connection, that connection should not be counted toward the
     number of concurrent connections.

     Further, this definition assumes that the ability (or lack thereof)
     to transfer data on a given connection is solely the responsibility
     of the DUT/SUT. For example, a TCP connection that a DUT/SUT has



Newman                       Informational                      [Page 6]

RFC 2647            Firewall Performance Terminology         August 1999


     left in a FIN_WAIT_2 state clearly should not be counted. But
     another connection that has temporarily stopped transferring data
     because some external device has restricted the flow of data is not
     necessarily defunct. The tester should take measures to isolate
     changes in connection state to those effected by the DUT/SUT.

   Unit of measurement:
     Concurrent connections
     Maximum number of concurrent connections

   Issues:

   See also:
     connections
     connection establishment time
     connection overhead

3.7 Connection

   Definition:
     A state in which two hosts, or a host and the DUT/SUT, agree to
     exchange data using a known protocol.

   Discussion:
     A connection is an abstraction describing an agreement between two
     nodes: One agrees to send data and the other agrees to receive it.

     Connections might use TCP, but they don't have to. Other protocols
     such as ATM also might be used, either instead of or in addition to
     TCP connections.

     What constitutes a connection depends on the application. For a
     native ATM application, connections and virtual circuits may be
     synonymous. For TCP/IP applications on ATM networks (where multiple
     TCP connections may ride over a single ATM virtual circuit), the
     number of TCP connections may be the most important consideration.

     Additionally, in some cases firewalls may handle a mixture of
     native TCP and native ATM connections. In this situation, the
     wrappers around user data will differ. The most meaningful metric
     describes what an end-user will see.

     Data connections describe state, not data transfer. The existence
     of a connection does not imply that data travels on that connection
     at any given time, although if data cannot be forwarded on a
     previously established connection that connection should not be
     considered in any aggregrate connection count (see concurrent
     connections).



Newman                       Informational                      [Page 7]

RFC 2647            Firewall Performance Terminology         August 1999


     A firewall's architecture dictates where a connection terminates.
     In the case of application or circuit proxy firewalls, a connection
     terminates at the DUT/SUT. But firewalls using packet filtering or
     stateful packet filtering designs act only as passthrough devices,
     in that they reside between two connection endpoints. Regardless of
     firewall architecture, the number of data connections is still
     relevant, since all firewalls perform some form of connection
     maintenance; at the  very least, all check connection requests
     against their rule sets.

     Further, note that connection is not an atomic unit of measurement
     in that it does not describe the various steps involved in
     connection setup, maintenance, and teardown. Testers may wish to
     take separate measurements of each of these components.

     When benchmarking firewall performance, it's important to identify
     the connection establishment and teardown procedures, as these must
     not be included when measuring steady-state forwarding rates.
     Further, forwarding rates must be measured only after any security
     associations have been established.

     Though it seems paradoxical, connectionless protocols such as UDP
     may also involve connections, at least for the purposes of firewall
     performance measurement. For example, one host may send UDP packets
     to another across a firewall. If the destination host is listening
     on the correct UDP port, it receives the UDP packets. For the
     purposes of firewall performance measurement, this is considered a
     connection.

   Unit of measurement:
     concurrent connections
     connection
     connection establishment time
     maximum number of concurrent connections
     connection teardown time

   Issues:
     application proxy vs. stateful packet filtering
     TCP/IP vs. ATM

     connection-oriented vs. connectionless

   See also:
     data source
     concurrent connections
     connection establishment





Newman                       Informational                      [Page 8]

RFC 2647            Firewall Performance Terminology         August 1999


     connection establishment time
     connection teardown
     connection teardown time

3.8 Connection establishment

   Definition:
     The data exchanged between hosts, or between a host and the
     DUT/SUT, to initiate a connection.

   Discussion:
     Connection-oriented protocols like TCP have a proscribed
     handshaking procedure when launching a connection. When
     benchmarking firewall performance, it is import to identify this
     handshaking procedure so that it is not included in measurements of
     bit forwarding rate or UOTs per second.

     Testers may also be interested in measurements of connection
     establishment time through or with a given DUT/SUT.

   Unit of measurement:
     not applicable

   See also:
     connection
     connection establishement time
     connection maintenance
     connection teardown

   Issues:
     not applicable

3.9 Connection establishment time

   Definition:
     The length of time needed for two hosts, or a host and the DUT/SUT,
     to agree to set up a connection using a known protocol.

   Discussion:
     Each connection-oriented protocol has its own defined mechanisms
     for setting up a connection. For purposes of benchmarking firewall
     performance, this shall be the interval between receipt of the
     first bit of the first octet of the packet carrying a connection
     establishment request on a DUT/SUT interface until transmission of
     the last bit of the last octet of the last packet of the connection
     setup traffic headed in the opposite direction.





Newman                       Informational                      [Page 9]

RFC 2647            Firewall Performance Terminology         August 1999


     This definition applies only to connection-oriented protocols such
     as TCP. For connectionless protocols such as UDP, the notion of
     connection establishment time is not meaningful.

   Unit of measurement:
     Connection establishment time

   Issues:

   See also:
     concurrent connections
     connection
     connection maintenance

3.10 Connection maintenance

   Definition:
     The data exchanged between hosts, or between a host and the
     DUT/SUT, to ensure a connection is kept alive.

   Discussion:
     Some implementations of TCP and other connection-oriented protocols
     use "keep-alive" data to maintain a connection during periods where
     no user data is exchanged.

     When benchmarking firewall performance, it is useful to identfy
     connection maintenance traffic as distinct from UOTs per second.
     Given that maintenance traffic may be characterized by short bursts
     at periodical intervals, it may not be possible to describe a
     steady-state forwarding rate for maintenance traffic. One possible
     approach is to identify the quantity of maintenance traffic, in
     bytes or bits, over a given interval, and divide through to derive
     a measurement of maintenance traffic forwarding rate.

   Unit of measurement:
     maintenance traffic
     forwarding rate

   See also:
     connection
     connection establishment time
     connection teardown
     connection teardown time

   Issues:
     not applicable





Newman                       Informational                     [Page 10]

RFC 2647            Firewall Performance Terminology         August 1999


3.11 Connection overhead

   Definition:
     The degradation in bit forwarding rate, if any, observed as a
     result of the addition of one connection between two hosts through
     the DUT/SUT, or the addition of one connection from a host to the
     DUT/SUT.

   Discussion:
     The memory cost of connection establishment and maintenance is
     highly implementation-specific. This metric is intended to describe
     that cost in a method visible outside the firewall.

     It may also be desirable to invert this metric to show the
     performance improvement as a result of tearing down one connection.

   Unit of measurement:
     bit forwarding rate

   Issues:

3.12 Connection teardown

   Definition:
     The data exchanged between hosts, or between a host and the
     DUT/SUT, to close a connection.

   Discussion:
     Connection-oriented protocols like TCP follow a stated procedure
     when ending a connection. When benchmarking firewall performance,
     it is important to identify the teardown procedure so that it is
     not included in measurements of bit forwarding rate or UOTs per
     second.

     Testers may also be interested in measurements of connection
     teardown time through or with a given DUT/SUT.

   Unit of measurement:
     not applicable

   See also:
     connection teardown time

   Issues:
     not applicable






Newman                       Informational                     [Page 11]

RFC 2647            Firewall Performance Terminology         August 1999


3.13 Connection teardown time

   Definition:
     The length of time needed for two hosts, or a host and the DUT/SUT,
     to agree to tear down a connection using a known protocol.

   Discussion:
     Each connection-oriented protocol has its own defined mechanisms
     for dropping a connection. For purposes of benchmarking firewall
     performance, this shall be the interval between receipt of the
     first bit of the first octet of the packet carrying a connection
     teardown request on a DUT/SUT interface until transmission of the
     last bit of the last octet of the last packet of the connection
     teardown traffic headed in the opposite direction.

     This definition applies only to connection-oriented protocols such
     as TCP. For connectionless protocols such as UDP, the notion of
     connection teardown time is not meaningful.

   Unit of measurement:
     Connection teardown time

   Issues:

   See also:
     concurrent connections
     connection
     connection maintenance

3.14 Data source

   Definition:
     A host capable of generating traffic to the DUT/SUT.

   Discussion:
     One data source may emulate multiple users or hosts. In addition,
     one data source may offer traffic to multiple network interfaces on
     the DUT/SUT.

     The term "data source" is deliberately independent of any number of
     users. It is useful to think of data sources simply as traffic
     generators, without any correlation to any given number of users.

   Unit of measurement:
     not applicable

   Issues:
     user



Newman                       Informational                     [Page 12]

RFC 2647            Firewall Performance Terminology         August 1999


   See also:
     connection
     user

3.15 Demilitarized zone

   Definition:
     A network segment or segments located between protected and
     unprotected networks.

   Discussion:
     As an extra security measure, networks may be designed such that
     protected and unprotected segments are never directly connected.
     Instead, firewalls (and possibly public resources such as HTTP or
     FTP servers) reside on a so-called DMZ network.

     DMZ networks are sometimes called perimeter networks.

   Unit of measurement:
     not applicable

   Issues:
     Homed

   See also:
     protected network
     unprotected network

3.16 Firewall

   Definition:
     A device or group of devices that enforces an access control policy
     between networks.

   Discussion:
     While there are many different ways to accomplish it, all firewalls
     do the same thing: control access between networks.

     The most common configuration involves a firewall connecting two
     segments (one protected and one unprotected), but this is not the
     only possible configuration. Many firewalls support tri-homing,
     allowing use of a DMZ network. It is possible for a firewall to
     accommodate more than three interfaces, each attached to a
     different network segment.

     The criteria by which access are controlled are not specified here.
     Typically this has been done using network- or transport-layer
     criteria (such as IP subnet or TCP port number), but there is no



Newman                       Informational                     [Page 13]

RFC 2647            Firewall Performance Terminology         August 1999


     reason this must always be so. A growing number of firewalls are
     controlling access at the application layer, using user
     identification as the criterion. And firewalls for ATM networks may
     control access based on data link-layer criteria.

   Unit of measurement:
     not applicable

   Issues:

   See also:
     DMZ
     tri-homed
     user

3.17 Goodput

   Definition:
     The number of bits per unit of time forwarded to the correct
     destination interface of the DUT/SUT, minus any bits lost or
     retransmitted.

   Discussion:
     Firewalls are generally insensitive to packet loss in the network.
     As such, measurements of gross bit forwarding rates are not
     meaningful since (in the case of proxy-based and stateful packet
     filtering firewalls) a receiving endpoint directly attached to a
     DUT/SUT would not receive any data dropped by the DUT/SUT.

     The type of traffic lost or retransmitted is protocol-dependent.
     TCP and ATM, for example, request different types  of
     retransmissions.  Testers must observe retransmitted data for the
     protocol in use, and subtract this quantity from measurements of
     gross bit forwarding rate.

   Unit of measurement:
     bits per second

   Issues:
     allowed vs. rejected traffic

   See also:
     allowed traffic
     bit forwarding rate
     rejected traffic






Newman                       Informational                     [Page 14]

RFC 2647            Firewall Performance Terminology         August 1999


3.18 Homed

   Definition:
     The number of logical interfaces a DUT/SUT contains.

   Discussion:
     Firewalls typically contain at least two logical interfaces. In
     network topologies where a DMZ is used, the firewall usually
     contains at least three interfaces and is said to be tri-homed.
     Additional interfaces would make a firewall quad-homed, quint-
     homed, and so on.

     It is theoretically possible for a firewall to contain one physical
     interface and multiple logical interfaces. This configuration is
     discouraged for testing purposes because of the difficulty in
     verifying that no leakage occurs between protected and unprotected
     segments.

   Unit of measurement:
     not applicable

   Issues:

   See also:
     tri-homed

3.19 Illegal traffic

   Definition:
     Packets specified for rejection in the rule set of the DUT/SUT.

   Discussion:
     A buggy or misconfigured firewall might forward packets even though
     its rule set specifies that these packets be dropped. Illegal
     traffic differs from rejected traffic in that it describes all
     traffic specified for rejection by the rule set, while rejected
     traffic specifies only those packets actually dropped by the
     DUT/SUT.

   Unit of measurement:
     not applicable

   Issues:








Newman                       Informational                     [Page 15]

RFC 2647            Firewall Performance Terminology         August 1999


   See also:
     accepted traffic
     policy
     rejected traffic
     rule set

3.20 Logging

   Definition:
     The recording of user requests made to the firewall.

   Discussion:
     Firewalls typically log all requests they handle, both allowed and
     rejected. For many firewall designs, logging requires a significant
     amount of processing overhead, especially when complex rule sets
     are in use.

     The type and amount of data logged varies by implementation.
     Testers may find it desirable to log equivalent data when comparing
     different DUT/SUTs.

     Some systems allow logging to take place on systems other than the
     DUT/SUT.

   Unit of measurement:
     not applicable

   Issues:
     rule sets

   See also:
     allowed traffic
     connection
     rejected traffic

3.21 Network address translation

   Definition:
     A method of mapping one or more private, reserved IP addresses to
     one or more public IP addresses.

   Discussion:
     In the interest of conserving the IPv4 address space, RFC 1918
     proposed the use of certain private (reserved) blocks of IP
     addresses. Connections to public networks are made by use of a
     device that translates one or more RFC 1918 addresses to one or
     more public addresses--a network address translator (NAT).




Newman                       Informational                     [Page 16]

RFC 2647            Firewall Performance Terminology         August 1999


     The use of private addressing also introduces a security benefit in
     that RFC 1918 addresses are not visible to hosts on the public
     Internet.

     Some NAT implementations are computationally intensive, and may
     affect bit forwarding rate.

   Unit of measurement:
     not applicable

   Issues:

   See also:

3.22  Packet filtering

   Definition:
     The process of controlling access by examining packets based on the
     content of packet headers.

   Discussion:
     Packet-filtering devices forward or deny packets based on
     information in each packet's header, such as IP address or TCP port
     number. A packet-filtering firewall uses a rule set to determine
     which traffic should be forwarded and which should be blocked.

   Unit of measurement:
     not applicable

   Issues:
     static vs. stateful packet filtering

   See also:
     application proxy
     circuit proxy
     proxy
     rule set
     stateful packet filtering

3.23 Policy

   Definition:
     A document defining acceptable access to protected, DMZ, and
     unprotected networks.







Newman                       Informational                     [Page 17]

RFC 2647            Firewall Performance Terminology         August 1999


   Discussion:
     Security policies generally do not spell out specific
     configurations for firewalls; rather, they set general guidelines
     for what is and is not acceptable network access.

     The actual mechanism for controlling access is usually the rule set
     implemented in the DUT/SUT.

   Unit of measurement:
     not applicable

   Issues:

   See also:
     rule set

3.24 Protected network

   Definition:
     A network segment or segments to which access is controlled by the
     DUT/SUT.

   Discussion:
     Firewalls are intended to prevent unauthorized access either to or
     from the protected network. Depending on the configuration
     specified by the policy and rule set, the DUT/SUT may allow hosts
     on the protected segment to act as clients for servers on either
     the DMZ or the unprotected network, or both.

     Protected networks are often called "internal networks." That term
     is not used here because firewalls increasingly are deployed within
     an organization, where all segments are by definition internal.

   Unit of measurement:

   not applicable

   Issues:

   See also:
     demilitarized zone (DMZ)
     unprotected network
     policy
     rule set
     unprotected network






Newman                       Informational                     [Page 18]

RFC 2647            Firewall Performance Terminology         August 1999


3.25 Proxy

   Definition:
     A request for a connection made on behalf of a host.

   Discussion:
     Proxy-based firewalls do not allow direct connections between
     hosts.  Instead, two connections are established: one between the
     client host and the DUT/SUT, and another between the DUT/SUT and
     server host.

     As with packet-filtering firewalls, proxy-based devices use a rule
     set to determine which traffic should be forwarded and which should
     be rejected.

     There are two types of proxies: application proxies and circuit
     proxies.

   Unit of measurement:
     not applicable

   Issues:
     application

   See also:
     application proxy
     circuit proxy
     packet filtering
     stateful packet filtering

3.26 Rejected traffic

   Definition:
     Packets dropped as a result of the rule set of the DUT/SUT.

   Discussion:
     For purposes of benchmarking firewall performance, it is expected
     that firewalls will reject all traffic not explicitly permitted in
     the rule set. Dropped packets must not be included in calculating
     the bit forwarding rate or maximum bit forwarding rate of the
     DUT/SUT.

   Unit of measurement:
     not applicable

   Issues:





Newman                       Informational                     [Page 19]

RFC 2647            Firewall Performance Terminology         August 1999


   See also:
     allowed traffic
     illegal traffic
     policy
     rule set

3.27 Rule set

   Definition:
     The collection of access control rules that determines which
     packets the DUT/SUT will forward and which it will reject.

   Discussion:
     Rule sets control access to and from the network interfaces of the

     DUT/SUT. By definition, rule sets do not apply equally to all
     network interfaces; otherwise there would be no need for the
     firewall. For benchmarking purposes, a specific rule set is
     typically applied to each network interface in the DUT/SUT.

     The tester must describe the complete contents of the rule set of
     each DUT/SUT.

     To ensure measurements reflect only traffic forwarded by the
     DUT/SUT, testers are encouraged to include a rule denying all
     access except for those packets allowed by the rule set.

   Unit of measurement:
     not applicable

   Issues:

   See also:
     allowed traffic
     demilitarized zone (DMZ)
     illegal traffic
     policy
     protected network
     rejected traffic
     unprotected network

3.28 Security association

   Definition:
     The set of security information relating to a given network
     connection or set of connections.





Newman                       Informational                     [Page 20]

RFC 2647            Firewall Performance Terminology         August 1999


   Discussion:
     This definition covers the relationship between policy and
     connections. Security associations (SAs) are typically set up
     during connection establishment, and they may be reiterated or
     revoked during a connection.

     For purposes of benchmarking firewall performance, measurements of
     bit forwarding rate or UOTs per second must be taken after all
     security associations have been established.

   Unit of measurement:
     not applicable

   See also:
     connection
     connection establishment
     policy
     rule set

3.29 Stateful packet filtering

   Definition:
     The process of forwarding or rejecting traffic based on the
     contents of a state table maintained by a firewall.

   Discussion:
     Packet filtering and proxy firewalls are essentially static, in
     that they always forward or reject packets based on the contents of
     the rule set.

     In contrast, devices using stateful packet filtering will only
     forward packets if they correspond with state information
     maintained by the device about each connection. For example, a
     stateful packet filtering device will reject a packet on port 20
     (ftp-data) if no connection has been established over the ftp
     control port (usually port 21).

   Unit of measurement:
     not applicable

   Issues:

   See also:
     applicaton proxy
     packet filtering
     proxy





Newman                       Informational                     [Page 21]

RFC 2647            Firewall Performance Terminology         August 1999


3.30 Tri-homed

   Definition:
     A firewall with three network interfaces.

   Discussion:
     Tri-homed firewalls connect three network segments with different
     network addresses. Typically, these would be protected, DMZ, and
     unprotected segments.

     A tri-homed firewall may offer some security advantages over
     firewalls with two interfaces. An attacker on an unprotected
     network may compromise hosts on the DMZ but still not reach any
     hosts on the protected network.

   Unit of measurement:
     not applicable

   Issues:
     Usually the differentiator between one segment and another is its
     IP address. However, firewalls may connect different networks of
     other types, such as ATM or Netware segments.

   See also:
     homed

3.31 Unit of transfer

   Definition:
     A discrete collection of bytes comprising at least one header and
     optional user data.

   Discussion:
     This metric is intended for use in describing steady-state
     forwarding rate of the DUT/SUT.

     The unit of transfer (UOT) definition is deliberately left open to
     interpretation, allowing the broadest possible application.
     Examples of UOTs include TCP segments, IP packets, Ethernet frames,
     and ATM cells.

     While the definition is deliberately broad, its interpretation must
     not be. The tester must describe what type of UOT will be offered
     to the DUT/SUT, and must offer these UOTs at a consistent rate.
     Traffic measurement must begin after all connection establishment
     routines complete and before any connection completion routine
     begins.  Further, measurements must begin after any security
     associations (SAs) are established and before any SA is revoked.



Newman                       Informational                     [Page 22]

RFC 2647            Firewall Performance Terminology         August 1999


     Testers also must compare only like UOTs. It is not appropriate,
     for example, to compare forwarding rates by offering 1,500-byte
     Ethernet UOTs to one DUT/SUT and 53-byte ATM cells to another.

   Unit of measurement:
     Units of transfer
     Units of transfer per second

   Issues:

   See also:
     bit forwarding rate
     connection

3.32 Unprotected network

   Definition:
     A network segment or segments to which access is not controlled by
     the DUT/SUT.

   Discussion:
     Firewalls are deployed between protected and unprotected segments.
     The unprotected network is not protected by the DUT/SUT.

     Note that a DUT/SUT's policy may specify hosts on an unprotected
     network. For example, a user on a protected network may be
     permitted to access an FTP server on an unprotected network. But
     the DUT/SUT cannot control access between hosts on the unprotected
     network.

   Unit of measurement:
     not applicable

   Issues:

   See also:
     demilitarized zone (DMZ)
     policy
     protected network
     rule set

3.33 User

   Definition:
     A person or process requesting access to resources protected by the
     DUT/SUT.





Newman                       Informational                     [Page 23]

RFC 2647            Firewall Performance Terminology         August 1999


   Discussion:
     "User" is a problematic term in the context of firewall performance
     testing, for several reasons. First, a user may in fact be a
     process or processes requesting services through the DUT/SUT.
     Second, different "user" requests may require radically different
     amounts of DUT/SUT resources. Third, traffic profiles vary widely
     from one organization to another, making it difficult to
     characterize the load offered by a typical user.

     For these reasons, testers should not attempt to measure DUT/SUT
     performance in terms of users supported. Instead, testers should
     describe performance in terms of maximum bit forwarding rate and
     maximum number of connections sustained. Further, testers should
     use the term "data source" rather than user to describe traffic
     generator(s).

   Unit of measurement:
     not applicable

   Issues:

   See also:
     data source

4. Security Considerations

   The primary goal of this memo is to describe terms used in
   benchmarking firewall performance. However, readers should be aware
   that there is some overlap between performance and security issues.
   Specifically, the optimal configuration for firewall performance may
   not be the most secure, and vice-versa.

   Further, certain forms of attack may degrade performance. One common
   form of denial-of-service (DoS) attack bombards a firewall with so
   much rejected traffic that it cannot forward allowed traffic. DoS
   attacks do not always involve heavy loads; by definition, DoS
   describes any state in which a firewall is offered rejected traffic
   that prohibits it from forwarding some or all allowed traffic. Even a
   small amount of traffic may significantly degrade firewall
   performance, or stop the firewall altogether. Further, the safeguards
   in firewalls to guard against such attacks may have a significant
   negative impact on performance.

   Since the library of attacks is constantly expanding, no attempt is
   made here to define specific attacks that may affect performance.
   Nonetheless, any reasonable performance benchmark should take into





Newman                       Informational                     [Page 24]

RFC 2647            Firewall Performance Terminology         August 1999


   consideration safeguards against such attacks. Specifically, the same
   safeguards should be in place when comparing performance of different
   firewall implementations.

5. References

   Bradner, S., Ed., "Benchmarking Terminology for Network
           Interconnection Devices", RFC 1242, July 1991.

   Bradner, S. and J. McQuaid, "Benchmarking Methodology for Network
           Interconnect Devices", RFC 2544, March 1999.

   Mandeville, R., "Benchmarking Terminology for LAN Switching Devices",
           RFC 2285, February 1998.

   Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G. and E. Lear,
           "Address Allocation for Private Internets", BCP 5, RFC 1918,
           February 1996.

6. Acknowledgments

   The author wishes to thank the IETF Benchmarking Working Group for
   agreeing to review this document. Several other persons offered
   valuable contributions and critiques during this project: Ted Doty
   (Internet Security Systems), Kevin Dubray (Ironbridge Networks),
   Helen Holzbaur, Dale Lancaster, Robert Mandeville, Brent Melson
   (NSTL), Steve Platt (NSTL), Marcus Ranum (Network Flight Recorder),
   Greg Shannon, Christoph Schuba (Sun Microsystems), Rick Siebenaler,
   and Greg Smith (Check Point Software Technologies).

7. Contact Information

   David Newman
   Data Communications magazine
   3 Park Ave.
   31st Floor
   New York, NY 10016
   USA

   Phone: 212-592-8256
   Fax:   212-592-8265
   EMail: dnewman@data.com









Newman                       Informational                     [Page 25]

RFC 2647            Firewall Performance Terminology         August 1999


8.  Full Copyright Statement

   Copyright (C) The Internet Society (1999).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















Newman                       Informational                     [Page 26]