1. Performance Objectives and Performance Components
Chapter 2
Performance Objectives and Performance Components
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

2. From Chapter 1 Step 1: Learning Top-Level Requirements
Many enterprise network designs fail because the executives involved have no clear-cut definition of success, and the objectives begin to vary, then thrash into chaos, during deployment.
As a network architect, your most important job is to articulate the real requirements.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

3. From Chapter 1 Step 2: Application Topology and Naming
First, of course, you need to identify the endpoints, which are users and servers.
Second, as you collect this information, introduce a naming structure to organize what you collect.
Should also collect information on the computer-
hardware type
operating systems
networking software type and version
Knowing the system and networking software gives you insight into latency
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

4. From Chapter 1 Step 3: Addressing, Routing, and Switching
Create a working cloud that interconnects your users and meets their needs.
The backbone provides connectivity among the user endpoints.
Steps 1 and 2, deal with a user-oriented worldview. Inside the network the requirements for efficient and reliable transmission are paramount.
Remember your high-level goal is cost-effectiveness.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

5. From Chapter 1 Step 4: Software
After you have decided on the routing structure and where to use switches to optimize performance, you need to select software functions to enable on the routers and switches.
For routers, a major software decision is the mechanism(s) they will use to find paths.
Addressing heavily interacts with software selection. If you choose to use unregistered addresses at the edge of the network, but use the global Internet for at least some of your connectivity, you need either to tunnel or translate some of those addresses.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

6. From Chapter 1 Step 5: Hardware and Media Speeds and feeds
Speeds of media
May or may not need switching on all interfaces
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

7. From Chapter 1 Step 6: Deployment Avoid doing massive cutovers,
During times that real users are on the network.
In hierarchical networks, it is best to start in one area, then add the core, and then add other areas.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

8. From Chapter 1 Phase 1: Test network capability
Phase 2: Initial trials with live data
Phase 3: Just before full cutover
Reflect workloads close to real environment
Cut back over if necessary
Phase 4: Production-level implementation
Look for problems under a full load.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

9. Chapter 2
Process of defining an internetwork that meets user performance requirements is iterative:
Quantify user performance needs:
Steps 1 & 2:define endpoints to be connected
Trace the path that the end-to-end user flow will take.
Step 3:address, routing and switching design.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

10. Requirements may exceed available budget.
Define internal constituents:
Median and interconnection devices
Requirements may exceed available budget.
Chapter 2 focuses on Step 2-Application Topology and Naming
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

11. 11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

12. Flows Unidirectional Traffic (One direction only)
Flows-unidirectional associations between source and one or more destinations.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

13. 11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

14. 11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

15. Application Response Time
Sum of measurements for a set of one-way transfers.
Non-interactive:one-way transfer.
Throughput and availability
Interactive:become difficult when human perceptual factors become involved.
Have response time
Local processing in the client before first communications sent
Queuing for transmission at the server’s communication interface
Network transfer from the client to the server
Processing in the server
Network transfer from the server to the client
Queuing in the client or gateway used by the client
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

16. Application Response Time
Responsible for true network delay:
Local processing in the client before first communications sent.
Queuing for transmission at the server’s communication interface.
Two unidirectional data relationships, one in each direction, for interactive applications.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

17. Categorizing Flows
Flows give ideas on the workload they will impose in a network.
Basic factors that establish throughput:
Sustainable avg rate
Peak rate
Approximate burst size
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

18. Categorizing Flows RFC 2430 PASTE categorize flows as:
Network control: routing updates, SNMP, etc.
Priority: App traffic sensitive to jitter(sensitivity to delay).
Best effort: Data traffic that can be retransmitted, or one-way voice or video transmission such as radio or tv.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

19. Categorizing Flows Flows can be set up: Implicitly Explicitly
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

20. Performance Values
User-perceived performance depends on the sum of the hop-by-hop unidirectional paths in the network plus host processing delays
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

21. Measuring Workload
ANSI X3.141-statistical considerations in measuring a workload in a network.
User traffic peak minutes after official work time.
Peak load could occur in night with backups, data distribution, database updates.
Busy hour;bimodal distribution. Morning and afternoon.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

22. IETF Benchmarking Methodology Working Group
Vendors specsmanship, smoke and mirrors.
Comparable data from different vendors with which to evaluate these devices.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

23. 11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

24. One way flow consists of some set of relays and outgoing links.
Need to determine whether dynamic routing is sufficient to find the path needed to meet the service requirement, or whether explicit traffic engineering is needed.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

25. Traffic Engineering and Queuing Policies
Traffice Engineering:
Explicitly assigning traffic to paths other than those that would be selected by ordinary dynamic routing.
Queuing Policies
Handling of flows in routers and switches.
If output port is busy, traffic destined for it either is dropped or buffered.
When port becomes available, a scheduler selects the queue from which it sends the next packet
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

26. Queuing Policies (cont)
Paths inside routers are governed by queuing policies
Links between routers are described with media specifications such as bandwidth and delay
Basic delays-sum of the link and relay delays in the end-to-end paths
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

27. Flows can be: Point-to-multipoint Point-to-point
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

28. 11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

29. Refining User-Oriented Performance
Edge of network
At the user device there are two basic kinds of application-significant performance
Response time for interactive apps
Throughput for non-interactive apps
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

30. X3.102 Model Technology-independent User oriented
Basis of national and international standards
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

31. X3.102
Three phases
Access: connection setup, other preparation such as flow requests.
User information transfer: actual communication.
Disengagement: process of disconnecting interface and making ready for new connection.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

32. Within each of these phases are:
Successful performance, measured in times.
Misperformance, measured as a probability.
Nonperformance, measured as a probability.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

33. 11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

34. Measurements taken go into a matrix of user-oriented performance parameters.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

35. 11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

36. X3.102 introduces the idea of interface responsibility.
If the source host is ready to transmit data through the network interface, it gives responsibility to the outgoing interface to accept the data.
Measurement of communications takes place while the channel between the source and the destination hosts is responsible for the interface.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

37. X3.102 introduces the idea of interface responsibility(cont)
If the source stops being ready to transmit, or the destination stops being ready to receive, the interface responsibility changes.
Must be a clear aggreement on network performance measurement and the contribution of hosts to user-visible performance, the network provider blames the user for poor performance and vice versa.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

38. Special Medium Considerations
Performance analysis deals with complex topologies by treating them as sets of point-to-point media.
Demand
Media that require real or virtual call setup at Layers 1, 2, or 3 are essentially unicast.
Demand services have different requirements at each end of the spectrum.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

39. Special Medium Considerations
Analog or ISDN low-bandwidth links
Extremely high bandwith virtual circuit services such as ATM.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

40. Special Medium Considerations
Analog or ISDN low-bandwidth
Make sure network management and routing protocols do not trigger unecessary/expensive calls.
Do not use routing protocols with periodic updates;likely to hold the link up indefinitely.
If using RIP and IGRP make sure they don’t propagate over the dial up
Be cautious using any routing protocol over dialup. They use keepalives.
OSPF and RIP(1 or 2) with demand support minimize the costs of calls.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

41. ISDN setup speeds are sufficiently fast that the incoming packets sent by the user, are stored in router RAM buffer until the demand circuit is ready to carry them out of the router.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

42. ATM Even faster setup times.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

43. Multicast Applications
Modern routing protocols such as OSPF and EIGRP use multicasting.(to transmit a message to multiple recipents at the same time).
MBONE
Multicast tunnels running over general IP networks.
Bandwidth intensive.
Two multicast classes:
Multipoint-to-multipoint
Point-to-multipoint
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

44. Host Issues
Many network performance problems are due to host, not network, capacity.
End-to-end
Sliding window designed to optimize throughput
RFC 1323
Traffic Generation
Computer/workstation traffic generated
Oversubscribed media-uanble to carry traffic
High-end Workstations and Servers-
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

45. Host Issues Broadcast and Multicast effects
Processing load placed on hosts
Traffic replication at Ports and Trunks
Best way to avoid broadcast storms is to have protocols that avoid them.
Hosts-CPU loading called broadcast radiation
Host has to process every broadcast and at least examine each multicast.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

46. 11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

47. Availability Fail to be available: Operational costs No connectivity
Too slow
Operational costs
Redundant mechanisms
Personnel
Two paths-share load. If one path fails user notices drop in performance but not failure
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

48. Availability Failure Scope of Downtime Edge Connectivity
WAN link fails
High Availability to General Internet
Endpoint multihoming-apps running on specific servers visible to the internet.
High Availability to Arbitrary Internet server
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

49. Availability High Availability to Selected Partners-extranets
Extranets use tunnels-software construct that carries payload information in a payload protocol over a delivery system.
Appears to end system as point-to-point connection.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

50. Availability VPN IP tunnels can interconnect members of a given VPN.
Performance cannot be controlled because it tunnels through ISP’s.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

51. 11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

52. Backbone
Need to consider what reliability level is needed from the backbone.
Use redundancy where it will help.
Excessive use can increase convergence.
Fault tolerance to be considered at the router and physical levels.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing

53. Service-Level Agreements
Excellent tools for requirements in the design level process.
Involve host application performance as well as the network performance.
Workload estimates:
Application
Overall environment
Consider availability.
Expectations of significant periods of downtime
Terms of mean time between(total) failures and mean time to repair.
11/29/2018
Designing Routing and Switching Architectures. Copyright 1999 Macmillan Technical Publishing