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ITEC 275 Computer Networks – Switching, Routing, and WANs

ITEC 275 Computer Networks – Switching, Routing, and WANs. Week 11 Robert D’Andrea. Some slides provide by Priscilla Oppenheimer and used with permission. Agenda. Learning Activities Industry Tests Build and Test a Prototype Write and Implement a Test Plan

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ITEC 275 Computer Networks – Switching, Routing, and WANs

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  1. ITEC 275 Computer Networks – Switching, Routing, and WANs Week 11 Robert D’Andrea Some slides provide by Priscilla Oppenheimer and used with permission

  2. Agenda • Learning Activities • Industry Tests • Build and Test a Prototype • Write and Implement a Test Plan • Tools for Testing a Network Design • Multicasting • QoS • Queuing and Traffic Shaping

  3. Reasons to Test • Verify that the design meets key business and technical goals • Validate LAN and WAN technology and device selections • Verify that a service provider provides the agreed-up service • Identify bottlenecks or connectivity problems • Determine optimization techniques that will be necessary

  4. Reasons to Test • Proving that your network design is better than a competing design • Passing an “acceptance test” that gives you approval to go forward with the network implementation • Convincing mangers and coworkers that your design is effective • Identifying any risks that might impede implementation and planning for contingencies • Determine how much additional testing might be required. Will the new system be deployed as a pilot and undergo additional testing before being implemented

  5. Testing Your Network Design • Use industry testing services • Build and test a prototype system • Use third-party and Cisco tools

  6. Respected Independent Test Labs • The Interoperability Lab at the University of New Hampshire (IOL) • ICSA Labs • Miercom Labs • AppLabs • The Tolly Group • Penetration Testing test your network and applications before the bad guys do.

  7. Simple verses Complex Network Designs • Simple network designs can rely on test results from vendors, independent labs, or trade journals to prove to your customer that your design will perform as intended. • Complex network designs require more considerations. • Testing should be implemented in-house • Testing will require more that component testing. There will be a need for unit, integration, and system testing.

  8. Scope of a Prototype System • It’s not generally practical to implement a full-scale system. • A prototype should verify important capabilities and functions that might not perform adequately. • Risky functions include complex, intricate functions and functions that were influenced by the need to make tradeoffs with other network components.

  9. Live Production Network • Perform initial testing during off-hours to minimize issues with user community, performance, and existing traffic flow • Perform final testing during normal hours and benchmark the performance • Perform final testing at various times to exercise network during typical loads and benchmark the performance

  10. Components of a Test Plan • Test objectives and acceptance criteria • The types of tests that will be run • Network equipment and other resources required • Testing scripts • The timeline and milestones for the testing project

  11. Components of a Test Plan • Test objectives and acceptance criteria Objectives and acceptance should be based on a customer’s business and technical goals Acceptance of test results are acceptable by both the customer and the tester. • Measure response time • Measure applications throughput • Measure the amount of time it takes to hear a dial tone using Voice over IP • Establish a baseline measurement of CRC errors

  12. Test Objectives and Acceptance Criteria • Specific and concrete • Based on business and technical goals • Clear criteria for declaring that a test passed or failed • Avoid biases and preconceived notions about outcomes • If appropriate, reference a baseline

  13. Types of Tests • Application response-time tests with terminal • Throughput tests (I/O) • Availability tests (failure test) • Regression tests (does the network perform similarly after changes were implemented)

  14. Resources Needed for Testing Test plan should include a network topology drawing for tester to be able to reference. A list of switches, routers, bridges, firewalls, servers, telephone equipment, and wireless access points. A list of documented version numbers for hardware and software. • Scheduled time in a lab either at your site or the customer’s site • Power, air conditioning, rack space, and other physical resources • Help from co-workers or customer staff • Help from users to test applications • Network addresses and names

  15. Example Test Script Workstations Server 1 Firewall Network A Network B Protocol Analyzer Protocol Analyzer

  16. Example Test Script (continued) • Test objective. Assess the firewall’s capability to block Application ABC traffic, during both light and moderately heavy load conditions. • Acceptance criterion. The firewall should block the TCP SYN request from every workstation on Network A that attempts to set up an Application ABC session with Server 1 on Network B. The firewall should send each workstation a TCP RST (reset) packet.

  17. Example Test Script (continued) • Start capturing network traffic on the protocol analyzer on Network A. • Start capturing network traffic on the protocol analyzer on Network B. • Run Application ABC on a workstation located on Network A and access Server 1 on Network B. • Stop capturing network traffic on the protocol analyzers.

  18. Example Test Script (continued) • Display data on Network A’s protocol analyzer and verify that the analyzer captured a TCP SYN packet from the workstation. Verify that the network layer destination address is Server 1 on Network B, and the destination port is port 1234 (the port number for Application ABC). Verify that the firewall responded to the workstation with a TCP RST packet.

  19. Example Test Script (continued) • Display data on Network B’s protocol analyzer and verify that the analyzer did not capture any Application-ABC traffic from the workstation. • Log the results of the test in the project log file. • Save the protocol-analyzer trace files to the project trace-file directory. • Gradually increase the workload on the firewall, by increasing the number of workstations on Network A one at a time, until 50 workstations are running Application ABC and attempting to reach Server 1. Repeat steps 1 through 8 after each workstation is added to the test.

  20. Example Test Script (continued) Host A sends a TCP SYNchronize packet to Host B Host B receives A's SYN Host B sends a SYNchronize-ACKnowledgement Host A receives B's SYN-ACK Host A sends ACKnowledge Host B receives ACK. TCP socket connection is ESTABLISHED. - See more at: http://www.inetdaemon.com/tutorials/internet/tcp/3-way_handshake.shtml#sthash.R92nBBrG.dpuf

  21. Tools for Testing a Network Design • Network-management and monitoring tools. These monitoring tools are used to alert network management to problems and report significant network problems. • Traffic generation tools • Modeling and simulation tools • QoS and service-level management tools • Protocol analyzer • http://www.topdownbook.com/tools.html

  22. Protocol Analyzer Tool • A protocol analyzer is used to analyze traffic behavior, errors, utilization, efficiency, and rates of broadcast and multicast packets. A protocol analyzer can be a computer program or a piece of computer hardware that can intercept and log traffic passing over a digital network or part of a network. As data streams flow across the network, the sniffer captures each packet and, if needed, decodes the packet's raw data, showing the values of various fields in the packet, and analyzes its content according to the appropriate RFC or other specifications.

  23. Simulation Tool • A simulation tool enables you to develop a model of a network, estimate the performance of the network and compare alternatives for implementing the network. iTrinegy Network Emulator (INE) products enable you to realistically recreate a wide variety of network conditions like latency, jitter, packet loss/error/reordering and bandwidth restrictions so that you can simulate environments such as Wide Area Networks (WANs), Wireless LANs, GPRS, 3G, IP over Radio / Radio over IP(RoIP), Satellite or MPLS networks.

  24. Reasons to Optimize • Meet key business and technical goals • Use bandwidth efficiently • Control delay and jitter • Reduce serialization delay • Support preferential service for essential applications • Meet Quality of Service (QoS) requirements

  25. IP Multicast

  26. IP Multicast Applications that take advantage of multicast include video conferencing, corporate communications, distance learning, and distribution of software, stock quotes, and news.

  27. IP Multicast Helps Optimize Bandwidth Usage • With IP multicast, you can send a high-volume multimedia stream just once instead of once for each user • Requires support for • Multicast addressing • Multicast registration (IGMP) • Multicast routing protocols

  28. IP Multicast Helps Optimize Bandwidth Usage To support IP multicasting, the Internet authorities have reserved the multicast address range of 01-00-5E-00-00-00 to 01-00-5E-7F-FF-FF for Ethernet and Fiber Distributed Data Interface (FDDI) media access control (MAC) addresses. 

  29. IP Multicast Helps Optimize Bandwidth Usage To map an IP multicast address to a MAC-layer multicast address, the low order 23 bits of the IP multicast address are mapped directly to the low order 23 bits in the MAC-layer multicast address. Because the first 4 bits of an IP multicast address are fixed according to the class D convention, there are 5 bits in the IP multicast address that do not map to the MAC-layer multicast address. 

  30. IP Multicast Addressing • Uses Class D multicast destination address • 224.0.0.0 to 239.255.255.255 • Converted to a MAC-layer multicast destination address • The low-order 23 bits of the Class D address become the low-order 23 bits of the MAC-layer address • The top 9 bits of the Class D address are not used • The top 25 bits of the MAC-layer address are 0x01:00:5E followed by a binary 0

  31. Internet Group Management Protocol (IGMP) • Allows a host to join a multicast group • Host transmits a membership-report message to inform routers on the segment that traffic for a group should be multicast to the host’s segment • IGMPv2 has support for a router more quickly learning that the last host on a segment has left a group

  32. Multicast Routing Protocols • Becoming obsolete • Multicast OSPF (MOSPF) • Distance Vector Multicast Routing Protocol (DVMRP) • Still used • Protocol Independent Multicast (PIM) • Dense-Mode PIM • Sparse-Mode PIM

  33. Multicast Routing Protocols What is PIM? Protocol-Independent Multicast (PIM) is a family of multicast routing protocol for Internet Protocol (IP) networks that provide one-to-many and many-to-many distribution of data over a LAN,WAN or the Internet. It is termed protocol-independent because PIM does not include its own topology discovery mechanism, but instead uses routing information supplied by other routing protocols.

  34. PIM (Protocol Independent Multicast) • Dense mode is used when there are many members (employees listen to a company president). PIM is similar to DVMRP. Both use reverse-path forwarding (RPF) mechanism to compute the shortest (reserve) path between a source and all possible recipients of a multicast packet. • Dense PIM does not require the computation of routing tables.

  35. PIM (Protocol Independent Multicast) What is PIM Dense Mode? Dense mode PIM is the older and simpler PIM mode. It works well in small networks where there are a large number of listeners, but is inefficient in larger network.

  36. PIM Dense Mode

  37. PIM Dense Mode

  38. PIM (Protocol Independent Multicast) • Sparse mode utilizes a rendezvous point (RP). A rendezvous point provides a registration service for a multicast group. • Sparse mode PIM relies on IGMP which let a host join a group by sending a membership-report message, and detach from a group by sending a leave message.

  39. PIM (Protocol Independent Multicast) PIM Sparse Mode (PIM-SM) explicitly builds unidirectional shared trees rooted at a rendezvous point (RP) per group, and optionally creates shortest-path trees per source. PIM-SM generally scales fairly well for wide-area usage.

  40. Serialization What is serialization? Serialization is the process of translating data structures or object state into a format that can be stored (for example, in a file or memory buffer, or transmitted across a network connection link) and reconstructed later in the same or another computer environment. When the resulting series of bits is reread according to the serialization format, it can be used to create a semantically identical clone of the original object.

  41. Serialization • Transmission delay or serialization delayIn a network based on packet switching, transmission delay (or store-and-forward delay) is the amount of time required to push all of the packet's bits into the wire. In other words, this is the delay caused by the data-rate of the link.Transmission delay is a function of the packet's length and has nothing to do with the distance between the two nodes. This delay is proportional to the packet's length in bits.

  42. Reducing Serialization Delay • Link-layer fragmentation and interleaving • Breaks up and reassembles frames • Multilink PPP • Frame Relay FRF.12 • Compressed Real Time Protocol • RTP is used for voice and video • Compressed RTP compresses the RTP, UDP, and IP header from 40 bytes to 2 to 4 bytes

  43. A Few Technologies for Meeting QoS Requirements • IETF controlled load service • IETF guaranteed service • IP precedence • IP differentiated services

  44. IP Type of Service Field • The type of service field in the IP header is divided into two subfields • The 3-bit precedence subfield supports eight levels of priority • The 4-bit type of service subfield supports four types of service • Although IP precedence is still used, the type of service subfield was hardly ever used

  45. IP Type of Service Field Type of Service Subfield Bit 0 3 4 5 6 7 D = Delay T = Throughput R = Reliability C = Cost Precedence D T R C 0 0 8 15 24 31 Bit Version Header Length Type of Service Total Length Identification Flags Fragment Offset Time to Live Protocol Header Checksum Source IP Address Destination IP Address Options Padding

  46. IP Differentiated Services (DS) Field • RFC 2474 redefines the type of service field as the Differentiated Services (DS) field • Bits 0 through 5 are the Differentiated Services Codepoint (DSCP) subfield • Has essentially the same goal as the precedence subfield • Influences queuing and packet dropping decisions for IP packets at a router output interface • Bits 6 and 7 are the Explicit Congestion Notification (ECN) subfield

  47. IP Differentiated Services (DS) Field 0 6 Differentiated Services Codepoint Explicit Congestion Notification 0 8 15 24 31 Header Length Version Differentiated Services Total Length

  48. Resource Reservation Protocol (RSVP) • RSVP complements the IP type-of-service, precedence, DSCP, and traffic-class capabilities inherent in an IP header. • RSVP supports mechanisms for hosts to specify QoS requirements for individual traffic flow. • RSVP can be deployed on LANs and enterprise WANs to support multimedia applications or other types of applications with strict QoS requirements.

  49. Resource Reservation Protocol (RSVP) • IP header type-of-service capabilities and RSVP are examples of QoS signaling protocols. • In-band signaling means that bits within the frame header signal to routers how the frame should be handled. • Out-of-band signaling means that hosts send additional frames, beyond data frames, to indicate that a certain QoS is desired for a particular traffic flow.

  50. Classifying LAN Traffic • IEEE 802.1p • Classifies traffic at the data-link layer • Supports eight classes of service • A switch can have a separate queue for each class and service the highest-priority queues first

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