06/18/22 Anue Systems, Inc. www.anuesystems.com 1 v1.0 - 20050426 D ocum entC over Sheet ProjectN um ber PN -3-X X X X (leave blank ifunknow n ornotapplicable) D ocum entTitle TIA -921 enhancem ents Source A nueSystem s C ontact N am e:CharlesW ebb 9111 Jollyville Rd, Suite 100 A ustin, TX 78759: Phone:512-527-0453 x102 Fax: Em ail: cwebb@ anuesystems.com D istribution TR-30.3 ForIncorporation Into TIA Publication x ForInformation Intended Purpose ofD ocum ent (Selectone) O ther(describe)- The docum ent to w hich this cover statem ent is attached is subm itted to a Form ulating G roup or sub-elem entthereofofthe Telecom m unications Industry A ssociation (TIA )in accordance w ith the provisionsofSections6.4.1–6.4.6 inclusive ofthe TIA Engineering M anualdated M arch 2005, allof w hich provisionsare hereby incorporated by reference. A bstract Severalareasforpossible im provem entorclarification ofthe existing TIA -921 and TIA -921-A m odels are presented, including bandw idth lim itation, duplicate testcases, CBR vsV BR sources, and tim e correlation offw d/rev im pairm ents. Telecommunications Industry Association TR-30.3/08-07-012 Arlington, VA July 14 - 15, 2008
v1.0 - 20050426
Jan 13, 2016
Telecommunications Industry AssociationTR-30.3/08-07-012 Arlington, VA July 14 - 15, 2008. v1.0 - 20050426. TIA-921 improvements Chip Webb, CTO – Anue Systems July 2008 - Arlington. www.anuesystems.com. Outline. Areas for future work Bandwidth Limitation Duplicate test cases - PowerPoint PPT Presentation
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04/21/23 Anue Systems, Inc.
www.anuesystems.com
1
v1.0 - 20050426
Document Cover Sheet
Project Number PN-3-XXXX (leave blank if unknown or not applicable)
Document Title TIA-921 enhancements
Source Anue Systems
Contact Name: Charles Webb 9111 Jollyville Rd, Suite 100 Austin, TX 78759:
Phone: 512-527-0453 x102 Fax: Email: [email protected]
Distribution TR-30.3
For Incorporation Into TIA Publication x For Information
Intended Purpose of Document (Select one) Other (describe) -
The document to which this cover statement is attached is submitted to a Formulating Group or sub-element thereof of the Telecommunications Industry Association (TIA) in accordance with the provisions of Sections 6.4.1–6.4.6 inclusive of the TIA Engineering Manual dated March 2005, all of which provisions are hereby incorporated by reference.
Abstract
Several areas for possible improvement or clarification of the existing TIA-921 and TIA-921-A models are presented, including bandwidth limitation, duplicate test cases, CBR vs VBR sources, and time correlation of fwd/rev impairments.
Telecommunications Industry Association TR-30.3/08-07-012Arlington, VA July 14 - 15, 2008
www.anuesystems.com
TIA-921 improvementsChip Webb, CTO – Anue Systems
July 2008 - Arlington
04/21/23 Anue Systems, Inc.
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Outline
Areas for future work Bandwidth Limitation Duplicate test cases Behavior with CBR versus VBR sources Time correlation of forward/reverse model
Conclusions
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Bandwidth limitations
TIA-921 does not require policing or shaping of user data
This is wrong for several reasons: In real-life, a rate-limited link drops packets
when the user bit rate exceeds the link bit rate.
In real life, a rate-limited link drops packet bursts that exceed the available buffer size.
In real life, a rate-limited link smooths out traffic bursts. The amount of that effect will depend on link utilization and the proportion of user traffic that that represents.
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Example: Bandwidth smoothing effect
Egress Queue
Output PktsInput Pkts
p5
time
p4p3p2p1 p6 p7 p8
time
p1 p2 p3 p4 p6 p7 p8
Note: P5 is dropped.
Note: The output bit rate for this example is ½ the input bit rate. Theeffect is even more pronounced forlarger ratios (such as T1/GigE).
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Duplicate Test cases
The TIA-921 model is unidirectional The code in the reference model ignores
reverse link bit rates, except for calculating LOOs
Examples: TIA-921: TC10 and TC19 are same (A2B) TIA-921-A: TC49 and TC73 are same (A2B)
Summary: TIA-921: 92 of the 120 have duplicates TIA-921-A: 48 of 96 Lan2Lan cases have dupes.
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TIA-921 Duplicates (A2B) direction
This is Same as This is Same as This is Same as This is Same as This is Same as4 32 27 18 54 68 79 114 115 805 33 28 34 55 69 80 115 116 826 35 29 36 56 42 48 62 81 117 117 8110 19 32 4 57 43 50 64 82 116 118 8311 20 33 5 58 44 83 118 119 11212 21 34 28 59 45 94 120 120 9413 22 46 60 35 6 60 13 22 46 95 121 121 9514 23 47 61 36 29 61 14 23 47 96 123 122 9715 24 49 63 42 48 56 62 62 42 48 56 97 122 123 9616 25 43 50 57 64 63 15 24 49 98 124 124 9817 26 44 58 64 43 50 57 104 106 108 110 125 12618 27 45 59 65 51 105 109 126 12519 10 46 13 22 60 66 52 106 104 108 11020 11 47 14 23 61 67 53 107 11121 12 48 42 56 62 68 54 108 104 106 11022 13 46 60 49 15 24 63 69 55 109 10523 14 47 61 50 43 57 64 70 72 110 104 106 10824 15 49 63 51 65 71 73 111 10725 16 52 66 72 70 112 11926 17 53 67 73 71 114 79
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TIA-921-A Lan2Lan Duplicates (A2B)
This is Same as This is Same as This is Same as49 73 69 93 89 6550 74 70 94 90 6651 75 71 95 91 6752 76 72 96 92 6853 77 73 49 93 6954 78 74 50 94 7055 79 75 51 95 7156 80 76 52 96 7257 81 77 5358 82 78 5459 83 79 5560 84 80 5661 85 81 5762 86 82 5863 87 83 5964 88 84 6065 89 85 6166 90 86 6267 91 87 6368 92 88 64
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Reverse model correspondence
For the reverse model of each rate combination, there exists at least one equivalent forward rate combination.
Examples: TIA-921: TC13 B2A same as A2B in
13,22,46&60 TIA-921-A: TC13 B2A same as A2B in 49&73
Some rate combos are symmetric and are thus their own reverse (e.g. 1,2,3)
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TIA-921 Reverse (B2A)Rev
(B2A)Same as
Fwd (A2B)Rev
(B2A)Same as
Fwd (A2B)Rev
(B2A)Same as
Fwd (A2B)Rev
(B2A)Same as
Fwd (A2B)Rev
(B2A)Same as
Fwd (A2B)Rev
(B2A)Same as
Fwd (A2B)
1 1 25 16 25 49 81 117 73 31 97 53 67 121 95 121 2 2 26 17 26 50 83 118 74 4 32 98 55 69 122 97 122 3 3 27 18 27 51 94 120 75 5 33 99 51 65 123 96 123 4 10 19 28 70 72 52 95 121 76 6 35 100 52 66 124 98 124 5 11 20 29 71 73 53 97 122 77 28 34 101 54 68 125 125 126 6 12 21 30 70 72 54 96 123 78 29 36 102 53 67 126 107 111 7 10 19 31 71 73 55 98 124 79 13 22 46 60 103 55 69 127 107 111 8 11 20 32 74 56 44 58 80 14 23 47 61 104 104 106 108 110 128 1289 12 21 33 75 57 45 59 81 15 24 49 63 105 104 106 108 110 129 12910 4 32 34 77 58 44 58 82 42 48 56 62 106 112 119 130 13011 5 33 35 76 59 45 59 83 43 50 57 64 107 125 126 131 13112 6 35 36 78 60 84 84 13 22 46 60 108 105 109 132 13213 13 22 46 60 37 89 61 85 85 14 23 47 61 109 105 109 133 13314 14 23 47 61 38 90 62 87 86 15 24 49 63 110 11315 15 24 49 63 39 92 63 86 87 42 48 56 62 111 12716 13 22 46 60 40 91 64 88 88 43 50 57 64 112 104 106 108 110 17 14 23 47 61 41 93 65 99 89 37 113 104 106 108 110 18 15 24 49 63 42 42 48 56 62 66 100 90 38 114 79 114 19 7 43 43 50 57 64 67 102 91 40 115 80 115 20 8 44 42 48 56 62 68 101 92 39 116 82 116 21 9 45 43 50 57 64 69 103 93 41 117 81 117 22 16 25 46 79 114 70 28 34 94 51 65 118 83 118 23 17 26 47 80 115 71 29 36 95 52 66 119 112 119 24 18 27 48 82 116 72 30 96 54 68 120 94 120
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TIA-921-A Reverse (B2A)Rev
(B2A)Same as
Fwd (A2B)Rev
(B2A)Same as
Fwd (A2B)Rev
(B2A)Same as
Fwd (A2B)Rev
(B2A)Same as
Fwd (A2B)1 1 25 7 49 13 73 192 2 26 8 50 14 74 203 3 27 9 51 15 75 214 4 28 10 52 16 76 225 5 29 11 53 17 77 236 6 30 12 54 18 78 247 25 31 31 55 37 79 438 26 32 32 56 38 80 449 27 33 33 57 39 81 4510 28 34 34 58 40 82 4611 29 35 35 59 41 83 4712 30 36 36 60 42 84 4813 49 73 37 55 79 61 61 85 85 67 91 14 50 74 38 56 80 62 62 86 86 68 92 15 51 75 39 57 81 63 63 87 87 69 93 16 52 76 40 58 82 64 64 88 88 70 94 17 53 77 41 59 83 65 65 89 89 71 95 18 54 78 42 60 84 66 66 90 90 72 96 19 49 73 43 55 79 67 61 85 91 67 91 20 50 74 44 56 80 68 62 86 92 68 92 21 51 75 45 57 81 69 63 87 93 69 93 22 52 76 46 58 82 70 64 88 94 70 94 23 53 77 47 59 83 71 65 89 95 71 95 24 54 78 48 60 84 72 66 90 96 72 96
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Model behavior, CBR versus VBR
A fundamental assumption is that the model calculates new impairment values for approximately each packet Thus we used 1ms update rate for 1k pps voice And we used a 50us update rate for DTV
But, if traffic is bursty, and a whole burst of packets arrives during a timeslot which is marked for drop, the entire burst can get clobbered merely by being unlucky.
The model should have a way to handle bursty traffic more correctly.
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Time correlation of fwd/rev For bidirectional emulation using the model,
we must create two instances of the model One for the forward link and one for the reverse.
These two models are not time correlated Therefore congestion in the forward link is
uncorrelated with congestion in the reverse link. Link failure and route flap are also uncorrelated.
I believe that in the real world there will be significant correlation between the two directions.
The model should have a way to mimic this behavior.
This leads to uncontrolled assymetry of delay Certain services may be sensitive to delay
assymetry e.g. Two-way time transfer: NTP, PTP and CESoETH
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Conclusions Bandwidth limiting and smoothing are
important missing components of the existing model and should be added.
The rate combinations contain some redundancy that leads to confusion. Further work is required to determine if there’s a better way to designate the various rate combinations
VBR traffic can be “unlucky” and get zapped. Further works is required to determine how to address this
Forward and reverse models have no time correlation. This should be added to the model.
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