【文章內容簡介】 ? Determine the authorization and authentication requirements for corporate branch offices, mobile users, and telemuters ? Identify any requirements for authenticating routes received from access routers or other routers ? Identify any requirements for host security such as physical security of hosts, user accounts, dated software, access rights on data, etc. 33 Presentation_ID 169。 1999, Cisco Systems, Inc. Identifying Manageability Requirements ? Isolate any requirements for fault management ? Isolate any requirements for accounting management ? Isolate any requirements for configuration management ? Isolate any requirements for performance management ? Isolate any requirements for security management 34 Presentation_ID 169。 1999, Cisco Systems, Inc. Extracting Application Requirements ? Document the names and types of new applications ? Document the names and types of new protocols ? Document the number of users who will use new applications and protocols ? Diagram the flow of information when new applications are introduced ? Diagram the flow of information of existing applications ? Identify peak hours of usage of new applications 35 Presentation_ID 169。 1999, Cisco Systems, Inc. Characterizing New Network Traffic ? Characterize traffic load ? Characterize traffic behavior ? Use tools such as the NETSYS Enterprise/Solver Performance Tools ? Use other tools that we discussed earlier, such as CiscoWorks, etc. 36 Presentation_ID 169。 1999, Cisco Systems, Inc. Identifying Performance Requirements ? Response time ? Accuracy ? Availability ? Maximum work utilization ? Throughput ? Efficiency ? Latency 37 Presentation_ID 169。 1999, Cisco Systems, Inc. Create a Customer Needs Specification Document ? Record the customer39。s requirements, business constraints, and the characteristics of the existing work 38 Presentation_ID 169。 1999, Cisco Systems, Inc. Characterizing Network Traffic ? One of the most difficult aspects of extracting a customer39。s requirements is to gain an understanding of how the customer39。s protocols behave. ? Characterizing work traffic and protocols requires you to understand broadcast behavior, frame size, windowing and flow control, and error recovery mechanisms. 39 Presentation_ID 169。 1999, Cisco Systems, Inc. Broadcast Behavior ? Desktop protocols such as AppleTalk, NetWare, NetBIOS, and TCP/IP require broadcast and multicast packets to find services and check for uniqueness of addresses and names ? Routing and bridging protocols, also use broadcasts and multicasts to share information about the interwork topology. 40 Presentation_ID 169。 1999, Cisco Systems, Inc. Broadcast Behavior ? Layer 2 switches forward broadcasts and multicasts, which bees a scalability issue as flat switched works bee larger. ? CPU Utilization. The work interface cards in a work station pass broadcasts and relevant multicasts to the CPU of the station. 41 Presentation_ID 169。 1999, Cisco Systems, Inc. Scalability Constraints for (Switched/Bridged) Flat Networks Protocol Maximum Number of Workstations IP 500 IPX 300 AppleTalk 200 NetBios 200 Mixed 200 42 Presentation_ID 169。 1999, Cisco Systems, Inc. Frame Size ? Using a frame size that is the maximum supported for the medium has a positive impact on work performance that is significant. ? Avoid increasing the MTU to larger than the maximum supported for the media traversed by the frames, in order to avoid fragmentation and reassembly of frames. ? Ether : 1500, Serial : 1500, Token Ring : 4464, ATM : 4470, FDDI : 4470, HSSI (HSA) : 4470 43 Presentation_ID 169。 1999, Cisco Systems, Inc. Efficiency Depending on Frame Size D a ta S ize inB y tesF ra me S izein B y tesOv e rh e a d Ma x imu mE fficie n c y1492 1518(ma x imu m)2 .5 % 9 7 .5 %974 1000 3 .8 % 9 6 .2 %474 500 7 .4 % 9 2 .6 %3 8 (n o P A D ) 6 4 b y tes(min imu m)5 0 .0 % 5 0 .0 %1 (p lu s 3 7b y tes o fP A D )6 4 b y tes(min imu m)9 8 .7 % 1 .3 %Source: Breyer and Riley, Switched a