There are three generations. The original Gen. 1 has been discontinued for some time. Either Gen 2 or the new Gen. 3 will handle 20 Mbps as a VoIP ALG and firewall. I would go for the Gen.3 as it has a significant horsepower boost although you might have longer leadtime to get one.
Mbps ratings are for the most part overrated and while figures don't lie, liars do figure. A lab scenario with 100% full MTU packets, no firewall, no crypto, no NAT, no services such as DHCP, QoS, and the like will produce some quite respectable numbers. In the real world every application is different so you can expect less than the sales brochure virtually all the time. Packets per second is often a better metric but those figures can be tweaked as well. Expect fine print with words like "up to" in such literature. Your mileage may vary, etc.
Real-world experience from a long-term Adtran customer (me) says the Gen. 2 units will handle 30 Mbps of mixed Internet, firewall, and VoIP without breaking much of a sweat. We're still waiting for our first Gen. 3 units to put through their paces.
Based on your mention of a PoE switch I would assume that the unit will be doing SIP to voice phones. The TA900 series has been rock solid in this application and is likely your best fit.
Please exercise caution using this or any VoIP technology for an alarm or elevator line. There's nothing from a performance or technical standpoint that would prevent such use, but these are cases where a plain old copper line is often your best choice for emergency reporting circuits. If the UPS powering your VoIP gear catches fire in the middle of the night, you'll want the fire alarm connected to a POTS circuit.
We're currently working with Product Management to provide marketed throughput numbers publicly, but as Jayh said there are several variables to consider when publishing throughput numbers. We must consider simple raw routing throughput with typical IMIX traffic, routing with Firewall & NAT enabled, along with advanced routing (e.g. FW, NAT, Traffic-Shaping, and QOS applied). As such, when we do post numbers publicly, each of these scenarios will be covered for every product.
In the meantime, Jayh is absolutely correct, in that the Ethernet-to-Ethernet throughput of the 2nd Gen TA 900e (with QoS, Traffic-Shaping, FW/NAT with 12.5% of traffic simulated voice traffic) is around 20-30mbps (aggregate throughput). This is true for all TA 900e 2nd Gen units, including the 2nd 900e Single DSP versions. However, the throughput of the new 3rd Gen 900e products is much higher given the newer (higher-end) processor, quadrupled memory, etc. While we still don't have solid (or official marketed throughput numbers) for the 900e 3rd Gen with QOS, Traffic-Shaping enabled, I can tell you the marketed throughput rate of the 3rd Gen with Firewall & NAT enabled is 100mbps. Though (unofficial) , initial testing with the 3rd Gen units has proven 50-60mbps with QOS, Traffic-Shaping, FW and NAT enabled is achievable...
Based on your current application requirements (20mbps throughput w/VQM, 2x10/100 Ethernet ports & 2xFXS), the 2nd Gen Total Access 908e (Single DSP) is our lowest-cost/best-fit solution for this application. As you'll see, the TA 908e Single DSP is MSRP priced at $545 less than the standard TA 908e. For more information, take a look at Part # 4242908L5 and/or select link below:
Thank you for the response! I wasn't aware of the single DSP product. What is the difference between the singe vs dual DSP? What does the second DSP give you?
The DSPs are used when a call enters the unit as RTP packetized voice such over a codec on a SIP (or MGCP) connection and leaves the unit as TDM such as PRI, T1 CAS, FXO, or FXS, or enters as TDM and leaves as RTP.
Each simultaneous call uses one DSP resource, and each DSP has 30 resources although I seem to recall that only about 28 of them can be used for calls, with a couple reserved for generating and/or detecting tones on call setup.
The non-"e" models contain one DSP. This means that a TA924 for example, can run out of DSPs if feeding both a busy T1-PBX and 24 FXS lines.
The "e" models contain two DSPs for a total of roughly 60 resources. So a 924e could run out of DSPs if feeding two busy PBXs and 24 FXS lines.
The 908e-L5 is a special 908e that is equipped with only one DSP. It is very useful for cases where you need the extra T1 or Ethernet ports only available in the "-e" units but you only need 28 or so simultaneous TDM-RTP calls. It is substantially less expensive than the dual-DSP 9XX-e models.
Note that a DSP isn't used for a SIP-to-SIP call such as proxy to IP phones or terminating SIP to an IP PBX via the ALG.
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