TÓPICOS AVANÇADOS EM REDES ADVANCED TOPICS IN NETWORKS

Transcription

1 Mestrado em Engenharia de Redes de Comunicações TÓPICOS AVANÇADOS EM REDES ADVANCED TOPICS IN NETWORKS Projecto de Rede / Sistema - Network / System Design 1

2 Hierarchical Network Design 2

3 Hierarchical Network Design The hierarchical network design model allows the design of a modular topology using scalable building blocks to meet evolving needs. The modular design makes the network easy to scale, understand, and troubleshoot by promoting deterministic traffic patterns. The building block components are the Access layer, the Distribution layer, and the Core (backbone) layer. The principal advantages of this model are its hierarchical structure and its modularity. 3

4 Hierarchical Network Design In a hierarchical design, the capacity, features, and functionality of a specific device are optimized for its position in the network and the role that it plays, promoting scalability and stability. The number of flows and their associated bandwidth requirements increase as they traverse points of aggregation and move up the hierarchy from access to distribution to core. Functions are distributed at each layer. A hierarchical design avoids the need for a fully-meshed network in which all network nodes are interconnected. In a hierarchical design, the building blocks of modular networks are easy to replicate, redesign, and expand, avoiding the redesign of the whole network each time a module is added or removed. In a hierarchical design, distinct building blocks can be put in-service and taken out-of-service without impacting the rest of the network. This capability facilitates troubleshooting, problem isolation, and network management. 4

5 Enterprise Hierarchical Network Design 5

6 The Core Layer The Core serves as the Backbone for the network. The Core needs to be fast and extremely resilient because every building block depends on it for connectivity. The core layer should be designed as a high-speed, Layer 3 (L3) switching environment utilizing only hardware-accelerated services. 6

7 The Distribution Layer The Distribution layer aggregates nodes from the access layer, protecting the core from high-density. The Distribution layer creates a fault boundary providing a logical isolation point in the event of a failure originating in the access layer. Load balancing, Quality of Service (QoS), and ease of provisioning are key considerations for the Distribution layer. Typically deployed as a pair of L3 switches for its connectivity to the Core of the network and L2 services for its connectivity to the Access layer. High Availability in the Distribution layer is provided through dual equal-cost paths both to the Core and from the Access layer. 7

8 The Access Layer The Access layer is the first point of entry into the network for edge devices, Network/Services Platforms. The switches in the Access layer are connected to two separate Distribution layer switches for redundancy. A robust Access layer provides High availability (HA) supported by many hardware and software attributes, adequate for Service Delivery. 8

9 Reliability, Maintainability, and Availability 9

10 Non-Stop High Availability The ability for devices to connect and for applications to function is dependent on the availability of the network. Availability is not a new requirement and historically has been the primary service requirement for most designs. The metrics of what availability means and the requirements for how available the network is have changed as a result of the growth in unified communications, high-definition multimedia, and the overall increasing dependence on the network for all business processes. The types of service metrics to use will depend on the design and the types of equipment (network devices) to implement in the network. 10

11 Non-Stop High Availability Availability is traditionally measured using a number of metrics, including the percentage of time the network is available or the number of nines such as five nines of availability: Reliability, in terms of Mean Time Between Failures (MTBF) and mean time between mission-critical failures (MTBCF) Maintainability, in terms of Mean Time to Repair (MTTR) Availability, in terms of MTBF, MTBCF, MTTR Optionally, uptime and downtime (as a percent of total time), error and loss rates at various levels, such as packet error rate, bit error rate (BER), cell loss ratio (CLR), cell misinsertion ratio (CMR), frame and packet loss rates The calculation of availability is based on a function of the Mean Time Between Failures (MTBF) of the components in the network and the Mean Time to Repair (MTTR) or how long it takes to recover from a failure. 11

12 Non-Stop High Availability Reliability is a statistical indicator of the frequency of failure of the network and its components and represents the unscheduled outages of service. Maintainability is a statistical measure of the time to restore the system to fully operational status, once it has experienced a fault. Availability (also known as operational availability) is the relationship between the frequency of mission-critical failure and the time to restore service. 12

13 Non-Stop High Availability Improving availability is achieved by either increasing the MTBF (reducing the probability of something breaking) or decreasing the MTTR (reducing the time to recover from a failure) or both. 13

14 Non-Stop High Availability The calculations for the system MTBF are based on the probability that one switch in a non-redundant (serial) network breaks, or both switches in a redundant (parallel) design break. 14

15 Non-Stop High Availability Redundancy and how redundancy is used in a design also affects the MTTR for the network. The time to restore service or data flows in the network is based on the time it takes for the failed device to be replaced or the time the network takes to recover data flows via a redundant path. The time it takes any operations team to replace a device is usually measured in hours or days rather than in minutes or seconds and the impact on the availability of the network can be significant if the appropriate degree of device redundancy is missing from the design. 15

16 Non-Stop High Availability 16

17 Non-Stop High Availability The second commonly used metric for measuring availability is Defects Per Million (DPM). DPM measures the impact of defects on the service from the end user perspective. It is often a better metric for determining the availability of the network because it better reflects the user experience relative to event effects. DPM is calculated by taking the total affected user minutes for each event, total users affected, and the duration of the event, as compared to the total number of service minutes available during the period in question. 17

18 Non-Stop High Availability The third metric to be considered in the network design for availability is the maximum outage that any application or data stream will experience during a network failure. Five minutes of outage experienced in the middle of a critical event has a significant impact on the carrier business. 18

19 Date Center Architecture 19

20 Data Center Architecture Data Centers are composed of devices that provide the following functions: Ensuring network connectivity, including switches and routers Providing network and server security, including firewalls and Intrusion Detection Systems (IDSs) Enhancing availability and scalability of applications, including load balancers, Secure Socket Layer (SSL) offloaders and caches 20

21 Data Center Architecture Data Center infrastructure design - critical requirements: High Availability - Avoiding a single point of failure and achieving fast and predictable convergence times Scalability - Allowing changes and additions without major changes to the infrastructure, easily adding new services, and providing support for hundreds dual-homed servers Simplicity - Providing predictable traffic paths in steady and failover states, with explicitly defined primary and backup traffic paths Security - Prevent flooding, avoid exchanging protocol information with rogue devices, and prevent unauthorized access to network devices 21

22 Data Center Architecture models The multi-tier model: The multi-tier model is the most common design in the carrier enterprise. It is based on the web, application, and database layered design supporting Service Delivery Architectures and carrier Business and Operations Support solutions. The multi-tier model relies on security and application optimization services to be provided in the network. The server-cluster model: The server cluster model is commonly associated with high-performance computing (HPC), parallel computing, and high-throughput computing (HTC) environments. 22

23 Data Center Multi-Tier model The multi-tier data center model is dominated by HTTP-based applications in a multi-tier approach. The following three tiers are used: Web-servers Application servers Database servers Multi-tier server farms can provide improved resiliency and security. Resiliency is improved because a server can be taken out of service while the same function is still provided by another server belonging to the same application tier. Security is improved because an attacker can compromise a web server without gaining access to the application or database servers. Web and application servers can coexist on a common physical server; the database typically remains separate. 23

24 Data Center Multi-Tier model core Carrier Core Network 24

25 Data Center Server-Cluster model When designing a large enterprise servercluster network, it is critical to consider specific objectives. No two clusters are exactly alike; each has its own specific requirements and must be examined from an application perspective to determine the particular design requirements. Take into account the following technical considerations: Latency, Mesh/partial mesh connectivity, High throughput, Oversubscription ratio, Jumbo frame support, Port density 25

26 Server-Cluster Two-Tier model 26

27 Server-Cluster Three-Tier model 27

28 Examples of Architecture Diagrams 28

29 A 3G CDMA Mobile System prod_white_paper0900aecd8042bd19_ps5940_products_white_paper.html 29

30 A Wireless carrier network 30

31 A Carrier s Core infrastructure (SDC) 31

32 Service Delivery Core (SDC) Access Networks Core Services Platforms OSS/BSS Databases ISP Network Interconnect 32

33 ISP Front-End Network (Web Services) ISP Access Network Carrier Data Center Internet Services AAA Server MIP HA Content Server 33

34 Carrier Transmission Network with SDH 34

35 Carrier Transmission Network with Gigabit Ethernet 35

36 Carrier Transmission Network with SDH/ATM/PDH 36

37 Carrier Transmission Network with IP/MPLS 37

38 TÓPICOS AVANÇADOS EM REDES ADVANCED TOPICS IN NETWORKS 38

39 References and Readings WWW TÓPICOS AVANÇADOS EM REDES ADVANCED TOPICS IN NETWORKS 39