Cisco ACI- Spine-Leaf Architecture

Today I am going to talk about the Cisco ACI architecture which is new Technology Architecture from Cisco side in Data Center space.

New Technology in data-center comes into picture in the form of spine-leaf topology where we can have the east west traffic to be propagate in the equidistance.

Spine-Leaf Architecture:
Spine-Leaf topologies are based at the near community structure. The time period originates from Charles Clos at Bell Laboratories, who posted a paper in 1953 describing a mathematical theory of a multi pathing, non-blockading, more than one-level community topology wherein to replace smartphone calls.

Spine-leaf is typically deployed as two layers: spines (like an aggregation layer), and leaves (like an get right of entry to layer). spine-leaf topologies provide excessive-bandwidth, low-latency, non-blocking server-to-server connectivity.

Fig 1.1- Cisco Spine-Leaf Architecture

Leaf (aggregation) switches are what offer devices get entry  to the material (the network of spine and Leaf switches) and are generally deployed on the top of the rack. typically, gadgets connect with the Leaf switches. gadgets may include servers, Layer four - 7 services (firewalls and cargo balancers), and WAN or net routers.

Leaf switches do not connect with different leaf switches (until jogging vPC in standalone NX-OS mode). however, each leaf should hook up with each spine in a full mesh. some ports on the leaf can be used for cease devices (commonly 10 Gigabits), and some ports might be used for the spine connections (commonly forty Gigabits).

Fig 1.2 Stages of the Leaf-Spine Network( Networks-baseline)
Fig 1.2 Stages of the Leaf-Spine Network( Networks-baseline)

Spine Topology:-
Spine (aggregation) switches are used to hook up with all Leaf switches, and are typically deployed at the stop or middle of the row. spine switches do not connect with different backbone switches. Spines function backbone interconnects for Leaf switches. typically, spines best connect with leaves, but when integrating a Cisco Nexus 9000 transfer into an current surroundings it's miles perfectly applicable to connect other switches, services, or devices to the spines.

All devices connected to the cloth are an same range of hops away from one another. This gives you predictable latency and high bandwidth among servers. The diagram in determine 6 indicates a easy two-tier design.

Fig 1.3 Design in Data-center ( Networks-Baseline )
Fig 1.3 Design in Data-center ( Networks-Baseline )

How we achieve this:-
With Leaf-spine configurations, all gadgets are exactly the equal quantity of segments away and comprise a predictable and consistent quantity of put off or latency for touring statistics. this is possible because of the brand new topology design that has best two layers, the Leaf layer and backbone layer.

The Leaf layer includes access switches that connect with devices like servers, firewalls, load balancers, and side routers. The backbone layer which is called as spine (made of switches that perform routing) is the spine of the network, where each Leaf switch is interconnected with each and each backbone transfer.

Fig 1.4 Layer 3 Spine-Leaf Fabric
Fig 1.4 Layer 3 Spine-Leaf Fabric

To allow for the predictable distance between devices on this -layered design, dynamic Layer three routing is used to interconnect the layers. Dynamic routing allows the exceptional direction to be determined and altered primarily based on responses to community trade. 

This type of network is for records center architectures with a focal point on “East-West” network site visitors. “East-West” visitors carries information designed to travel within the statistics middle itself and now not outdoor to a one-of-a-kind site or network.  

This new method is a method to the intrinsic barriers of Spanning Tree with the capacity to utilize different networking protocols and methodologies to obtain a dynamic community.
Fig 1.5 Core Fabric ( Networks-Baseline)
Fig 1.5 Core Fabric ( Networks-Baseline)

 Rest of the Story:-
With Leaf-spine, the network makes use of Layer three routing. All routes are configured in an active country via using identical-value Multipath (ECMP). This lets in all connections to be applied on the equal time while still last solid and averting loops within the network.

With traditional Layer 2 switching protocols like Spanning Tree on three-tiered networks, it ought to be configured on all devices efficaciously and all the assumptions that Spanning Tree Protocol (STP) is predicated on need to be taken into account (one of the smooth errors to make when configuring STP is with mislabeling device priorities that could lead to an inefficient route setup). 

The removal of STP between the get entry to and Aggregation layers in lieu of Layer three routing consequences in a miles greater strong surroundings.

Every other gain is the convenience of adding additional hardware and capability. when oversubscription of links occurs (which means that more visitors is generated than may be aggregated onto the lively link at one time), the capacity to make bigger potential is simple. an additional spine switch may be added and uplinks can be prolonged to each Leaf transfer, ensuing inside the addition of interlayer bandwidth and reduction of the oversubscription.

Whilst device port potential turns into an issue, a new Leaf switch may be added by way of connecting it to each spine and adding the community configuration to the switch. the convenience of growth optimizes the IT department’s procedure of scaling the community with out dealing with or disrupting the Layer 2 switching protocols.

Leaf-Spine Worries:
The alternative principal drawback comes from the use of Layer three routing. This eliminates the spanning of VLANs (digital LAN) throughout a network. 

VLANs in a Leaf-spine network are localized to each person Leaf switch; any VLAN segments which are left on a Leaf switch are not reachable through the alternative Leaf's. this could create troubles with a scenario inclusive of guest virtual system mobility inside a statistics middle.

Leaf-Spine Cases:
web scale packages where server area within the network is static could benefit from the implementation of Leaf-backbone. the use of Layer 3 routing among layers of the structure does no longer avoid net scale programs because they do not require server mobility. 

The removal of Spanning Tree Protocol (STP) results in a greater stable and dependable community overall performance of East-West traffic flows. Scalability of the structure is likewise improved.

Organization packages leveraging cellular digital machines (e.g. vMotion) create an trouble while a server wishes to be supportable anywhere inside the records middle.  the use of Layer three routing and shortage of VLANs extending among Leaf's breaks this requirement.

To paintings round this trouble, an answer such as software program defined Networking (SDN) may be employed, which creates a virtual Layer 2 above/on pinnacle of the Leaf-backbone network.  This lets in servers to transport around in the environment with impunity at no detriment to “East-West” overall performance, scalability, and stability attributes of a Leaf-backbone community topology.