The granular control over Layer 2 in today’s smart switches might surprise net veterans

Smart switches have grown up to look more like the managed side of the family

This vendor-written tech primer has been edited by Network World to eliminate product promotion, but readers should note it will likely favor the submitter’s approach.

In the gap between plug and play unmanaged Ethernet switches and fully managed enterprise switches, vendors added the so called “smart switch,” which offer light management features to unmanaged gigabit Ethernet devices. Today, smart switches targeted at small-to-medium-size business run the gamut in terms of manageability and feature sets. 

The appeal of basic network management features for a small business stems from the need for performance and security. Plug and play and start right away—that’s what every start up wants—then later on, they need basic configurations and features to accommodate growth as needed.

Smart switches offer basic QoS features: prioritizing traffic by class, and segmenting the networked endpoints into a few VLANs, which can help in the first rounds of expansion. Smart switches help with cost of ownership as well, with control over network infrastructure via a graphical user interface (GUI) and hardware priced well below enterprise LAN equipment. This can be valuable to cost-conscious organizations not yet ready to hire a full-time network engineer.

Smart evolution

Over the past few years, the smart switch segment has undergone an arms race with vendors piling on robust features. Whereas once smart switches resembled their unmanaged kin, they’ve since grown up to look more like the managed side of the family.

“Smart switches have definitely grown up into the higher level capabilities,” says Brian Fulmer, a central California IT manager experienced enough to have Novell NetWare on his resume. “The management side of things has changed from the individual device level to the network level; the other big change has been the actual hardware features and capabilities versus the nominal sophistication of the operating system of the switches, and how you touch that.”

If you need to troubleshoot the LAN, a smart switch looks way beyond the ‘unplug-yell-replace’ repair method intrinsic to unmanaged switches. With a smart switch you get port mirroring to view and investigate packet size and throughput, and it can be configured for standard Remote Monitoring (RMON) performance reporting. Broadcast storm event logging are commonplace in smart switches as well.

The granular level of control over Layer 2 in today’s smart switches might surprise veteran network professionals. QoS and traffic prioritization, LACP protocol for link aggregation, VLAN subnets in rapid spanning tree configuration with up to three MST instances--a smart switch will do that for you. “Smart switches are offering more and more speed and greater capabilities for the smaller business network; some vendors even offer stackable switches allowing you to manage multiple switches as a single unit,” confirms Scott Padgett, Newegg’s commercial networking field engineer. “No need to go to a managed switch for a gigabit business network anymore.”

Drawing the line of between smart and managed

Padgett agrees, however, that as much as smart switches have evolved, we should probably draw the line at Layer 3 of the OSI model for anything less than a managed switch. This might offend a few marketers who go as far as introducing new sub-levels of the OSI to describe how close smart switch can get to a full-on router with the packet handling.

“Shopping for switches can be extremely frustrating, because claiming an 802.x standard (or others) on a list of features does not mean a full implementation of that standard,” Fulmer, the veteran IT manager, points out. “That's nothing new in technology; the nice thing about standards is there are so many of them—caveat emptor.” Your mileage will vary when it comes to advanced smart switch capabilities from a cross-vendor standpoint. You have to get pretty deep into the cut sheets to ferret out some of the differences. 

Network manufacturers offer varying tiers of smart management in sub-managed switches. Naming conventions are inconsistent across vendors which creates confusion, but in general, network engineers should identify clear lines of demarcation if you dig into packet management features.

Application level QoS and security

Control over the transmission schedule is elemental for traffic handling features that define the QoS capabilities. A current generation smart switch willprioritize packet routing by drawing on data in DSCP field in the IP header, or the VLAN Priority field in the VLAN tag, to classify packets across Layer 3 of the OSI. A smart switch configuration will prioritize bandwidth for voice packets for VoIP endpoints over data packets for computer endpoints, for instance. In contrast, a fully-managed enterprise switch uses the traffic classifier to classify packets at a finer level, down to the application layer (Layer 4 of the OSI). In a network that has subnets accessing several applications hosted in the datacenter, managed switch configurations prioritize packet traffic to endpoints using applications that are more latency-sensitive.

Additionally, a fully managed switch can be configured to recalculate the checksum in the Time to Live (TTL) IPv4 header of the routed packet for each “hop” between networked devices. This makes sure that packets are not prematurely dropped in complex networks, and allows network architects more freedom to add network segmentation and enhance security.

If your network involves centralized, locally hosted application servers and databases and endpoints on various subnets, it is common practices to have central managed switches directing traffic out to smart switches that handle packets for subnet endpoints. “Core switches in the same room as the servers need to be fully managed and CLI configurable, full stop,” advises Fulmer. “Even a hundred-user network has enough complexity that the visibility and configurability of real managed switches is going to pay off.”

“Beyond the core, smart switches make a lot of sense for cost reasons,” Fulmer adds. “If you don't have servers because your infrastructure and services are all cloud based, which is far more common now than even a few years ago, then you can skip managed switches and do your network services—DNS, DHCP, routing—in your router/firewall/UTM, with LAN connectivity handled by smart switches.  This is in broad terms, obviously.”

Managed core, smart periphery

A managed core/smart periphery is the setup that enterprise systems engineer Dennis Diaz works with at ABC Television Studios in Los Angeles. “Some of those super expensive managed switches have a pretty hefty GUI but most the engineers are used to the CLI for setting the configurations and use that almost exclusively,” Diaz says. “We are so accustomed to the CLI that it’s just faster that way.”

Not every engineer works with the same methodology, but when asked to draw the line between smart switch and managed switch, eventually it circles back to the same question. What do you want to do with your networking?

This strikes at the golden rule of IT purchasing: buy for your needs rather than the features. The larger a network gets, the more useful the flexibility of managed switch becomes. For Diaz at ABC-TV, a GUI comes in handy for making small, usually temporary changes in the network. “I’ll use the smart switch GUI for simple VLAN tagging as needed on a subnet, or I’ll use the CLI to set up the bulk of the network rules and make small tweaks to with the GUI.” The graphical interface has its place.

Everything comes back to needs. Each business network is unique, but the common thread between large networks and their smaller counterparts is performance and security. The best way to address these needs changes at scale. Wise IT managers look a year or two ahead to have the appropriate equipment and personnel in place anticipating growth and network expansion—the fact that smart switches play nicely with managed switches, even across vendor lines, is a huge plus for starting smart and growing from there.     

Kalle is responsible for global strategy, execution and P&L for this emerging business unit, developing networking products for small and medium-sized businesses, broadband service providers, and government channels.