Jayshree Ullal the former star Cisco Senior Vice President responsible for Cisco's $10 billion in revenue Datacenter Nexus 7000, Catalyst 4500 and 6500 switch product group and services line, has embraced cloud networking as her next gig by joining high-performance switch vendor Arista Networks as its President and Chief Executive Officer.
 "I am delighted to join Arista. |
"The combination of an outstanding team, innovative hardware and software technology and the Cloud Networking vision drew me to this company.
"I look forward to creating a unique focus for our strategic customers, partners and channels," said Ullal.
Obviously excited about her "next gig" as she calls it, Jayshree detailed Arista's Cloud Networking vision in her blog yesterday.
"Cloud networks simply cannot be achieved with today’s monolithic networking software stacks. I am very excited by Arista’s Extensible Operating System (EOS) innovations and its impact on Cloud Networking.
"By separating process and state, EOS can distribute software and configuration information across the entire fabric, enabling seamless consistency across the infrastructure. This in turn enables to provision clouds, add new servers or services, and update images and patches with simplicity and ease, and to automate every step of the provisioning process."
Jayshree adds that there are many attributes that customers need to consider for cloud network fabrics that directly affect the choice of switch and software architecture. Some of the key considerations are below (the text and graphics below are drawn from Jayshree's blog as well as other information found on Arista's Web site):
| 1. Scalability: |
The cloud network must scale to the overall level of throughput required to ensure that it does not become the bottleneck. This means the cloud networking fabric must handle throughputs that will reach trillions of packets in the near future.
Attributes of Cloud Networking:
The cloud network must deliver microsecond latency across the entire network fabric since low latency improves application performance and server utilization.
For latency sensitive applications, 10 Gigabit Ethernet is a major improvement:
The cloud network must provide predictable performance to service a large number of simultaneous applications in the network, including video, voice and web traffic.
EOS: An Extensible Operating System
The key to EOS benefits is its unique multi-process state-sharing architecture that consists of multiple processes interacting with a central shared state repository called Sysdb (system database). This architecture is shown below.
EOS Multi-Process State-Sharing Architecture
EOS derives its benefits from the essential characteristics of the architecture above:
| A. | Each switch function is in a separate address space, including each CLI session, each hardware device driver, and each protocol daemon such as routing protocols, spanning tree, and LACP. |
| B. | Sysdb holds all state, while agents perform all processing. Sysdb is an address space that purely holds state and delivers state updates from one agent to another. For example, when a link goes down, a port driver updates the link state in sysdb, which delivers the update to the SNMP service, which then sends a trap. Agents may contain copies of Sysdb state for efficiency, but all state is recoverable from Sysdb whenever needed. Like a traditional database engine, Sysdb itself is ultra-reliable because it contains no application code. |
| C. | Processing is in user space. Protocol operation, management function, and device management, including hardware device drivers, run in user address spaces, not in the kernel. By keeping the vast majority of processing out of the kernel, system stability is enhanced, and extensibility is simplified, because adding a new user process to Linux is simpler and safer than adding kernel-level code. |
Real-time upgrades and image/patch management in a large cloud-network is a daunting challenge to network administrators. A vastly simpler approach is required to handle networks of this size, which automates provisioning, monitoring, maintenance, upgrading, and troubleshooting.
The EOS multi-process state-sharing architecture is also the key to reducing maintenance windows by allowing more maintenance tasks to be performed during normal switch operation. EOS’ in-service software upgrade (ISSU) capability relies on the ability to restart the patched agent without disrupting switch operation. Packet forwarding is unaffected by the module upgrade process, so there is no user-perceptible downtime. ISSU is illustrated below.
ISSU - EOS’ in-service software upgrade
Cloud networks operate 24x7, so downtime is not an option. This requires a network architecture that offers self-healing and the ability for transparent in-service software updates.
On most switches, any software fault results in a reload, resulting in seconds or even minutes of downtime. Under EOS, any fault is contained within the agent or driver where the fault originated. If the fault causes the agent to crash, then the EOS process manager (ProcMgr) restarts it immediately. If the fault causes the agent to hang or loop, ProcMgr detects the condition and restarts the agent. Thus, faults within EOS are self healing. This process is shown below.
Fault Containment and Self Healing
Related stories:
Ex-Cisco exec drawn to start-up Arista's software architecture
Ex-Cisco exec Ullal lands at data center start-up
Former Cisco rising star to head up data center switching firm
Do you think Jayshree has made the right choice embracing cloud networking as her next gig?
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