Белая книга для Cisco Cisco Prime Virtual Network Analysis Module (vNAM) 6.1
2-3
Cisco Virtualized Multiservice Data Center (VMDC) Virtual Services Architecture (VSA) 1.0
Design Guide
Chapter 2 VMDC VSA 1.0 Design Overview
Terminology
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Static network designs make assumptions about traffic patterns and the locations of servers and
services. If, as often happens over time, those assumptions become incorrect, complex redesign can
be necessary. A fabric switching system based on FabricPath can be easily expanded as needed with
additional access nodes in a plug and play manner, with minimal operational impact.
services. If, as often happens over time, those assumptions become incorrect, complex redesign can
be necessary. A fabric switching system based on FabricPath can be easily expanded as needed with
additional access nodes in a plug and play manner, with minimal operational impact.
•
Switches that do not support FabricPath can still be attached to the FabricPath fabric in a redundant
way without resorting to STP.
way without resorting to STP.
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FabricPath L2 troubleshooting tools provide parity with those currently available in the IP
community for non-fabric path environments. For example, the Ping and Traceroute features now
offered at L2 with FabricPath can measure latency and test a particular path’s among the multiple
equal-cost paths to a destination within the fabric.
community for non-fabric path environments. For example, the Ping and Traceroute features now
offered at L2 with FabricPath can measure latency and test a particular path’s among the multiple
equal-cost paths to a destination within the fabric.
Reliability Based on Proven Technology
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Although FabricPath offers a plug-and-play user interface, its control protocol is built on top of the
powerful IS-IS routing protocol, an industry standard that provides fast convergence and is proven
to scale in the largest service provider (SP) environments.
powerful IS-IS routing protocol, an industry standard that provides fast convergence and is proven
to scale in the largest service provider (SP) environments.
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Loop prevention and mitigation is available in the data plane, helping ensure safe forwarding
unmatched by any transparent bridging technology. FabricPath frames include a time-to-live (TTL)
field similar to the one used in IP, and an applied reverse-path forwarding (RPF) check.
unmatched by any transparent bridging technology. FabricPath frames include a time-to-live (TTL)
field similar to the one used in IP, and an applied reverse-path forwarding (RPF) check.
Efficiency and High Performance
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With FabricPath, equal-cost multipath (ECMP) protocols used in the data plane can enable the
network to find optimal paths among all the available links between any two devices.
First-generation hardware supporting FabricPath can perform 16-way ECMP, which, when
combined with 16-port 10 gigabits per second (Gbps) port-channels, represents bandwidth of up to
2.56 terabits per second (Tbps) between switches.
network to find optimal paths among all the available links between any two devices.
First-generation hardware supporting FabricPath can perform 16-way ECMP, which, when
combined with 16-port 10 gigabits per second (Gbps) port-channels, represents bandwidth of up to
2.56 terabits per second (Tbps) between switches.
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With FabricPath, frames are forwarded along the shortest path to their destination, reducing the
latency of the exchanges between end stations compared to a STP based solution.
latency of the exchanges between end stations compared to a STP based solution.
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FabricPath needs to learn at the edge of the fabric only a subset of the MAC addresses present in the
network, enabling massive scalability of the switched domain.
network, enabling massive scalability of the switched domain.
Terminology
FabricPath comprises two types of nodes: spine nodes and leaf nodes. A spine node is one that connects
to other switches in the fabric and a leaf node is one that connects to servers. These terms are useful in
greenfield scenarios but may be vague for migration situations, where one has built a hierarchical
topology and is accustomed to using traditional terminology to describe functional roles.
to other switches in the fabric and a leaf node is one that connects to servers. These terms are useful in
greenfield scenarios but may be vague for migration situations, where one has built a hierarchical
topology and is accustomed to using traditional terminology to describe functional roles.
In this document, we expand our set of terms to correlate fabric path nodes and functional roles to
hierarchical network terminology:
hierarchical network terminology:
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Aggregation-Edge—A FabricPath node that sits at the “edge” of the fabric, corresponding to an
aggregation node in a hierarchical topology.
aggregation node in a hierarchical topology.
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Access-Edge—A FabricPath node that sits at the edge of the fabric, corresponding to an access node
in a hierarchical topology.
in a hierarchical topology.
These nodes may perform L2 and/or L3 functions. At times, we also refer to an L3 spine or a L3 edge
node to clarify the location of Layer 2/Layer 3 boundaries and distinguish between nodes that are
performing Layer 3 functions versus L2-only functions.
node to clarify the location of Layer 2/Layer 3 boundaries and distinguish between nodes that are
performing Layer 3 functions versus L2-only functions.