Fast vs. Gigabit Ethernet for SurveillanceBy Ethan Ace, Published Mar 13, 2012, 08:00pm EDT
This guide is intended to help users decide when to use 100 Mbps Fast Ethernet vs 1 Gbps Ethernet in surveillance deployements. It covers:
- The basics of Ethernet, Fast vs. Gigabit
- Power over Ethernet support
- Cost differences
- When to use Fast Ethernet
- When to use Gigabit Ethernet
- 10 Gigabit Ethernet
- The future of Ethernet in surveillance
Ethernet, in the context of most networks, consists of two separate standards:
- Fast Ethernet: Fast Ethernet is the most commonly used standard, capable of 100 Mbps speeds. It is also commonly referred to simply as "Ethernet" or "10/100", though this are technically misnomers, which refer also to the older, original 10 Mbps standard, as well. Fast Ethernet is the basis of most networks, surveillance and otherwise, and is found in the majority of switches, PCs, and surveillance equipment on the market today.
- Gigabit Ethernet: Gigabit Ethernet (GbE) is capable of 10x the speed of Fast Ethernet, up to 1000 Mbps, or 1 Gbps. It has historically been used for switch-to-switch connections between network closets, or connecting servers to the network, due to the larger amount of traffic in these scenarios. It has seen limited use in connecting desktop PCs in most environments, simply because these additional speeds are unnecessary for most users.
These two terms actually consist of multiple different standards for copper and fiber Ethernet. Users selecting fiber equipment should be careful, however, as there is much more variation in fiber standards, which differ by distance, topology, and cable type.
Power over Ethernet
Power over Ethernet is supported on both Fast and Gigabit Ethernet. Previous iterations of the PoE and GbE standards were incompatible, but today, PoE-capable gigabit switches are available. These are largely unnecessary in surveillance, as most equipment does not require gigabit speeds nor is it equipped with gigabit connections. Gigabit PoE is more often used for wireless equipment, as speeds are often higher than 100 Mbps.
Moving from Fast Ethernet to gigabit is a moderate cost increase. For example, 8-port Cisco 300 series switches, with PoE, compare as follows:
$100 across the total cost of a system is not a significant increase, but budget-conscious users should be aware using GbE only when necessary.
When to Use Fast Ethernet
Fast Ethernet (100 Mb/sec) is used for connections to field devices, such as cameras, encoders, and I/O modules. Rarely do these devices support gigabit speeds. However, gigabit switches feature 10/100/1000 Mbps auto-sensing ports, meaning that the switch port will negotiate down to 100 Mbps speeds if a Fast Ethernet device is connected. Despite rapid increases in resolution in the past few years, camera streams are simply not large enough to warrant the use of Gigabit Ethernet for the bulk of the network.
When to Use Gigabit Ethernet
Though its use in connecting between camera and switch is unnecessary, Gigabit Ethernet does have three key uses in surveillance systems:
- Connecting Switches: When connecting switches to each other, whether in the same rack, or between multiple wiring closets, gigabit speeds are often preferred, if not required. For example, assume a switch handling twenty 4 Mbps streams, a total of 80 Mbps, is to be connected to another switch at the head end. This total required throughput is beyond what a Fast Ethernet link is likely to provide, requiring a gigabit uplink instead.
- Connecting Servers: When connecting servers to a surveillance network, gigabit speeds may be required. Similar to the above switch example, a 10/100 link may be unable to handle throughput required by a server. This is more common in larger systems, as small systems may be well below Fast Ethernet's usable bandwidth.
- Storage Networks: When using network-based storage, Gigabit Ethernet should be used. In enterprise-level systems, when connecting servers to SAN equipment, gigabit networks are typically preferred, using a dedicated network. At these levels, likely at least 30-40 cameras, Fast Ethernet simply cannot manage the throughput required between server and SAN. Even in small systems using NAS storage, the bandwidth consumed by camera streaming, one or more viewing clients, and potentially retrieving archived video may be more than a 100 Mbps link can sustain.
10 Gigabit Ethernet (10GbE)
The only likely use for 10GbE in surveillance is for storage interconnects, in cases where throughput is higher than a gigabit network can support. Beyond this, its added bandwidth and cost are unneeded. For the most part, 10 Gigabit Ethernet is used in data center interconnects and in internet routing, where huge amounts of traffic are being passed. 10GbE has a maximum distance of 30m on Cat 6, requiring Cat 6A for full 100m distance. On multimode fiber it may run up to 400m, and up to 10km on singlemode.
Future Ethernet Needs
We expect that Fast Ethernet will remain standard on cameras for years to come. With even today's highest-resolution cameras well-supported by Fast Ethernet, it will take dramatic increases in resolution at full frame rates to make gigabit necessary. Additionally, we expect compression will continue to improve, lessening the impact of resolution increases, at least somewhat. For these reasons, GbE will most likely remain relegated to backbone and storage connections, instead of everyday use.
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