COMNET III CACI

More documents

Recommendations

Info

The question on what details to incorporate into an ATM simulation is also partly governed by the functions and capabilities of COMNET III. Examining the obtainable results gives an indication what statistics are calculated and hence what details should be included in the model in order to calculate those details. So what results are provided by COMNET III? Basically, three different categories of results are reported: • Utilization statistics • Delay statistics • Error statistics COMNET III provides detailed reports on the utilization of the different network devices. Nodes, links or buffers for example have capacity parameters (in terms of processing speed or link speed), against which utilization percentages can be calculated. These are reported at various levels of details. Similarly, COMNET III provides numeric results about different networking delay, again at various levels of detail. Message, packet, transmission or setup delays are all included in the reports. With regards to the error statistics, COMNET III records the number of dropped cells, link failures, node failures or even individual disk read / write errors should these be in the model. By looking at these reports, a number of modeling principles become apparent. Most importantly, COMNET III does not model the contents of individual messages, cells or even frames. Not that this is impossible! The contents are simply not required to compute the above statistics. To compute the delay statistics, only the length of the messages, cells and frames as well as their respective overhead are needed, not the contents in terms of the individual bit values. Similarly, in order to model the concept of a virtual channel within the network, it is not necessary to actually represent network addresses and set their values in the cell header. An easier approach is to take a global view of the network and assume that the names given to the networking devices are globally known. So the routing algorithm is based on the node names and therefore does not have to set or inspect actual network addresses in the cell header. This is an example of the difference between the simulation approach and the emulation approach. Yet another simplification which can be made in simulation modeling relates to the use of statistical functions. Modeling frame or cells errors again does not have to be explicitly done by a link changing a bit in the frame or cell. A statistical function can be used to determine whether the frame or cell has been subjected to noise and is therefore erred. Again, this means that the cell contents do not have to be explicitly represented in order to model a particular function. These examples illustrate some of the different methods used in simulation modeling which distinguish it from emulation. It is important for you to remember that not every single detailed function in an ATM network has to be modeled and that some functions are replicated by other techniques. After all, the purpose of the simulation is to replicate the functionality of the network operations, not to emulate them. 8
Table 1 gives you an overview of the ATM modeling capabilities of COMNET III. It lists the main concepts as identified in the previous chapters, as well as whether they can be modeled or not. It also provides you with an indication as to which COMNET III concepts are used to model the respective ATM concepts. Please note that this table only provides a rough overview. The details are explained in the rest of this manual. ATM Topic Concept Modeled in COMNET III? Service Classes CBR rt-VBR nrt-VBR ABR UBR YES COMNET III Concepts Session Sources & Transport Protocol / Rate Control Remarks Section in Part 1 3.3 3.4 3.4 3.5 3.6 Section in Appendix A.1 Traffic Contract / Traffic Descriptors QoS Conformance Checking Rules B-ISDN Model PCR SCR MBS MCR CDVT Max CTD Mean CTD CDV CLR CET SECBR CMR CER SECBR CMR Control Plane Traffic User Plane Traffic Mgmt Plane Traffic YES YES NO IMPLIED PARTIAL YES PARTIAL Transport Protocol / Rate Control Simulation Results Transport Protocol / Policing Message Sources, Triggers, Message & Session Sources Message & Session Sources, Buffering Functions Built-into UPC/NPC Functions simulated which are important to compute the available statistics Functions Simulated which are important to compute the available statistics 3.2.2 A.2.1 3.2.2 A.2.2 A.2.2 3.2.2 A.2.3 A.3 A.3 A.3 9
Page 1 and 2: COMNET III Application Notes: Model
Page 3 and 4: Appendices……………………
Page 5 and 6: 2.2 Underlying Assumptions A number
Page 7: only those details which are signif
Page 11 and 12: Network Interfaces Connection Admis
Page 13 and 14: 3.2 Overview of COMNET III’s Mode
Page 15 and 16: To generate ATM traffic, you would
Page 17 and 18: 3.2.3 Other Protocols over ATM The
Page 19 and 20: 3.4 Modeling CBR Services A fundame
Page 21 and 22: UPC/NPC conformance for the CBR tra
Page 23 and 24: 3.5 Modeling VBR Services To model
Page 25 and 26: Figure 5: VBR buffer limit. As illu
Page 27 and 28: The remarks made under the previous
Page 29 and 30: control parameters as well as to ex
Page 31 and 32: In order for the RM cells to indica
Page 33 and 34: 3.7 Modeling UBR Services As descri
Page 35 and 36: For the FM functions, a distinction
Page 37 and 38: Bus Bus 1..n CPU Ports Ports Line C
Page 39 and 40: 4. Example Applications In the firs
Page 41 and 42: The particular QoS parameters of in
Page 43 and 44: CBR AAL1 VBR AAL3/4 ABR AAL3/4 Basi
Page 45 and 46: After running the model under both
Page 47 and 48: 4.2 TCP/IP vs. ATM at the Desktop T
Page 49 and 50: Note that she has decided to reduce
Page 51 and 52: The voice mail traffic is given the
Page 53 and 54: 4.3 Modeling ATM LANE Networks This
Page 55 and 56: The model topology consists of a nu
Page 57 and 58: Connected to the LES is a single CO
Page 59 and 60:
Figure 17 depicts a modified model
Page 61 and 62:
To model this architecture, COMNET
Page 63 and 64:
The OFF command is a global process
Page 65 and 66:
The respective connection utilizati
Page 67 and 68:
A. Perspectives on ATM - Brief Revi
Page 69 and 70:
This integration of the different n
Page 71 and 72:
available, or it will accept to est
Page 73 and 74:
Version 4.0 of the ATM Forum’s tr
Page 75 and 76:
A.3 The B-ISDN Protocol Reference M
Page 77 and 78:
Class A B C D AAL Type AAL1 AAL2 AA
Page 79 and 80:
Higher layer PDU (1-65535 bytes) Co
Page 81 and 82:
Link 1 ATM Switch VCI = 1 Link 2 VP
Page 83 and 84:
FDDI ATM Router ATM Switch Private
Page 85 and 86:
Input Ports Output Ports Figure 30:
Page 87 and 88:
In addition to the internal switchi
Page 89 and 90:
B.1.1 Resource Management Policies
Page 91 and 92:
Finally, the setup request is forwa
Page 93 and 94:
intermediary node, the local CAC fu
Page 95 and 96:
Arrival of a cell at time ta(k) X
Page 97 and 98:
CLP value? 0 1 GCRA using PCR(CLP=0
Page 99 and 100:
B.2.2.3 Available Bit Rate Conforma
Page 101 and 102:
control scheme requires more compli
Page 103 and 104:
B.3 Management Services We will now
Page 105 and 106:
In the second dimension, the OAM ce
Page 107 and 108:
• SECBR = Severely Errored Cell B
Page 109 and 110:
Note that the node detecting the fa
Page 111 and 112:
Glossary and Acronyms: The terms in
Page 113 and 114:
NNI* nrt-VBR OAM cells PCR PDU* PT
show all

COMNET III CACI

Create successful ePaper yourself

Delete template?

Save as template?