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Designing and Selecting a Cisco AS5350 or AS5400 Universal Gateway

Overview
When you design an AS5350 or AS5400 series gateway, you have several decisions to make. First, make sure you know all the details of your application, including type of traffic, codecs, number of required concurrent sessions needed, and type and number of trunk lines. Decide if you want a gateway from the AS5350 line or the AS5400 line and the particular model. Then choose trunk cards and DSP cards to match your application.

Step-By-Step Gateway Design

Choose your chassis. The AS5400 is a 2U gateway with 7 expansion slots, while the AS5350 is a 1U gateway with 3 expansion slots. Aside from that, the two lines are functionally equivalent. There are three AS5400 models - the AS5400 base unit (250MHZ processor), AS5400HPX (397MHZ processor) and AS5400XM (750 MHZ processor plus ethernet ports have been upgraded to gigabit). The AS5350 line includes the base AS5350 (250MHZ CPU) and the AS5350XM (750 MHZ CPU and gigabit ethernet). The slots on all these models can be provisioned with trunk cards, and one of two types of DSP cards, either the high-density packet voice/fax digital signal processor (PVDM2-64) cards, or the universal DFC cards (at present you cannot mix PVDM2 and DFC cards in a chassis). Generally, all these cards (discussed in more detail below) can be installed in any model. However, PVDM2 cards can only be installed in AS5350XM and AS5400XM chassis. Also, if you are planning a 'soft switch' IP-to-IP or transcoding type of gateway, you'll need to choose the AS5350XM or AS5400XM. For basic H323 or SIP traffic, the basis AS5350 and AS5400 will be fine up to 8PRIs, and for basic origination/termination via H323, the base AS5400 will work well up to 16PRIs. For SIP or more complex codecs, we recommend you use the HPX or XM above 8PRIs, and the XM is generally preferred above 400 ports for SIP. Also note - as mentioned above - that the newer PVDM2 hardware requires the XM chassis.

Decide if you need AC or DC power. Is non-redundant or a redundant power needed? (All AS5400 gateways have dual/redundant power, while nonredundant power is standard in AS5350s, although the redundant option is available).

What trunk signaling is used? For example, signaling protocols include T1 or E1 Primary Rate Interface (PRI), channel associated signaling (CAS), and E1/R2 (make sure the gateway supports the country-specific signaling you need - click here for a checklist provided by Cisco. What trunk types will you use and how many (T1/E1/CT3)?

---The trunk card options are 2CT1, 2CE1, 4CT1, 4CE1, 8CT1, 8CE1, CT3, and CT3A (Certain XM chassis configurations require the newer CT3a trunk card - that is, CT3 card version 07 of above - for DS3 circuits). These can be used in any model of AS5350 or AS5400. If you are designing an IP-to-IP gateway, you may not need any trunk cards at all.

---Is any special cable/connector needed to connect the trunks? For example, DB15, RJ-45 (or RJ-48C), BNC, or other cables may be needed to connect the E1/T1 trunks to the gateway. Normally ordinary patch cables will be fine.

• Your choice of DSP modules will depend on the types of traffic and codecs that will be used. G711, G729? H323 or SS7? Is Signaling System 7 (SS7) required? If so, then you should explore using the Cisco PGW 2200 Softswitch, or other gateways such as the Cantata IMG1010 that integrate SS7 support. You will need to use the Integrated Signaling Link Terminal (SLT) feature to integrate these gateways into an SS7 network.

–--The maximum number of calls supported on one chassis depends on the application. In general, the AS5350/AS5400 line is designed to handle a maximum of up to 672 sessions (648 using the DFC hardware). Using the high-density packet voice/fax feature card (PVDM2 hardware), the Cisco AS5350 supports up to 8 PRIs, while the AS5350XM supports up to 16PRIs or CT3 (672) G.711 voice or fax calls, while the AS5400 and AS5400HPX support up to 16PRIs or CT3, and the AS5400XM supports up to 20PRIs or CT3.

–--Choose the DSP module type, and the right combination of cards to support your needs. There are two types of DSPs: the traditional DFC card (either the NP108 or NP60), or the AS5X-FC carrier card(s) populated with PVDM2-64 modules. The principal differences are that the DFC cards support a fixed number of voice/data sessions regardless of traffic type, whereas the PVMD2 hardware offers higher densities and some additional CODEC and feature support, but resource consumption is variable and depends on the type of traffic (higher complexity traffic uses more of a PVDM2's 64 resources - tables below provide more details) .  Although Cisco advises using the PVDM2 hardware for voice and DFC hardware for dialup, in fact they are interchangeable except for the distinctions drawn here. Details of these two types of DSP cards follows. Your final choice may depend more on relative economics - and since these hardware options are so similar in what they do, that's ok.

(1)  PVDM2 Hardware: These high density packet voice/fax feature modules are installed on a special carrier card (AS5X-FC); 1 to 6 DSP modules (AS5X-PVDM2-64) can be installed on each carrier card, providing from 64 to 384 voice, data, and fax ports per card, based on the codecs used. (PVDM2 modules use up more resources with higher complexity codecs). They can only be installed in XM chassis. The PVDM2 has the advantages of supporting higher densities (number of total ports) and some additional codecs (such as G728) as described below. Each PVDM2-64 card supports 64 G711 sessions, 32 medium complexity, and 24 high complexity. As a rule of thumb, to calculate the number of PVDM2-64s you need, do this calculation: multiply the total number of low complexity ports by 1, the number of medium complexity ports by 2, and the number of high complexity ports by 2.67. Sum these products, and divide the sum by 64, and the result is the number of PVDM2-64s you need.

(2) Universal voice/data DFC hardware: These cards include the NP108 or DL108 (108 universal ports) and NP60 or DL60 (60 universal ports). Sometimes they are referred to as 'dial' or 'vufc' cards, but once again, they are all functionally equivalent - the only important difference is that some cards are 60 port and some are 108 port. They support 60 or 108 voice and data ports, irrespective of  the codec used (whereas the PVDM2 consumes DSP resources based on CODEC complexity).

• Make sure you have enough DRAM and Flash to support your IOS and configuration. Higher densities and more complex IOS versions require more.

IP-to-IP Configurations: The AS5350XM and AS5400XM can also be used as IP-to-IP gateways, typically as transcoding gateways. In IP-to-IP gateways (sometimes referred to as softswitches), voice, video, or other traffic comes in via an ethernet port, is processed and passed out again via an ethernet port. Transcoding gateways (sometimes called session border controller types of gateways) are particular types of IP-to-IP gateways that convert the traffic from one CODEC to another - for example G711 to G729. Pure transcoding gateways don't need PRI trunk cards, because all the traffic is handled via ethernet. Special IOS versions and configurations are required to support these applications. If the unit will be used as an IP-to-IP Gateway, that is as a session border controller (SBC) which facilitate direct IP connectivity between independent VoIP and video networks, then the gateway should be configured as a Cisco Multiservice IP-to-IP Gateway.

Click here to access our Cisco AS5350 series product catalog.

Click here to access our Cisco AS5400 series product catalog.