Traffic demands have spiked dramatically over the past five years, and gigabit Ethernet isn’t cutting it in enterprise networks anymore. While many companies have started making the transition from 1G to 10G, the next transition is pretty steep.
After 10G, you have a costly choice between 40G and 100G network speeds and most companies just don’t have the resources to make the jump.
Port channel architecture (a general term for Cisco's EtherChannel®) is a stop-gap approach to meeting these bandwidth demands. Infrastructure migration is always the end-goal, but increasing network speeds is a decision that could take years to finalize. Instead, port channel architecture virtually widens the data pipes to help enterprises scale capacity.
In other words, enterprises could have four 1GB links emulating 4GB of bandwidth using this architecture and forgo paying for the next bandwidth tier. To take advantage of this technology, architects must configure their networks to support aggregated and load balanced traffic well-above what the network can normally manage.
Redundancy protocols and inefficiencies make it even more complicated. In this post, I’ll cover the Spanning Tree Protocol (STP) that blocks redundant links, TRILL, and PGaP from Cisco as they pertain to EtherChannel.
Spanning Tree Protocol (STP)
Spanning Tree Protocol, or STP, was created to choose a root bridge and build loop-free paths to that root for all bridges in the network—in other words, STP stops redundant links from eating up a business’ bandwidth.
STP is not ideal for architects searching for ways to increase network speeds quickly. If there’s a faster alternative path, it’s blocked altogether. The result? Your network capacity will never reach its fullest potential. Like anything that’s completely streamlined, STP trades efficiency for predictability.
That’s where TRILL comes in.
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The Transparent Interconnection of Lots of Links (TRILL)
While many companies still rely on STP, the majority of businesses looking to increase their network speeds have moved to TRILL. TRILL is a routing protocol network standard which does away with STP’s streamlined service.
TRILL is a far more efficient use of the network infrastructure because it allows Ethernet frames to take direct paths outside of the main streamline. TRILL can run while also running STP.
TRILL and STP both exist in Layer 2 (the Data Link Layer) which limit their ability to help enterprises expand capacity. For port channel architecture, you need a Layer 3 switch.
Port Aggregation Protocol (PAgP)
Let’s return to the initial problem: an enterprise’s network speeds don’t match up with available network tiers—some are too hefty and others don’t provide enough bandwidth, and there isn’t an option in between.
You wouldn’t use a plane to go from your house to your neighbor’s, but you would when you have larger loads that need to travel long distances.
EtherChannel exists in Layer 3 and is supported by Cisco’s proprietary PAgP. With vendor-agnostic port channel architecture, network managers can take a standard 10G connection and turn it into two or four physical links that are recognized as one virtual pipeline without having to be concerned with the proprietary PGaP. This yields 20G or 40G of bandwidth in both the eastbound and westbound directions—and 40G or 80G of traffic overall. It allows the traffic to flow down one virtual lane despite the fact that there are up to four separate physical links.
EtherChannel supports different packet distribution mode, doing away with TRILL and STP’s rigid standardization processes, and it provides the most flexible solution to enterprise-level bandwidth problems.
Need to know more?
Whether your business needs to make the jump from 1G to 10G, or somewhere between 10G and 40G or 100G, port channel architecture is a safe bet to immediately address bandwidth needs (as long as network managers ensure visibility with proper connectivity).
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