Specifications
ESI Communications Servers Sales Overview
8
Advanced IP telecommunications capabilities
1
A key advantage of ESI Communications Servers is the robust infrastructure that governs both locally LAN-based IP
telephony and remote IP applications. Each ESI Communications Server complies with major industry standards. This
ensures the best audio quality experience for ESI Communications Server IP users, regardless of their location.
• User Datagram Protocol (UDP)
• Layer 3 QoS support via Differentiated Services (Diffserv)
• Packet compression levels of G.711 (for locally installed IP stations), G.726 (for remotely installed IP stations), and G.729 (for
Esi-Link connectivity)
2
• 802.3 100Base-TX Ethernet interfaces
• Layer 2 Quality of Service (QoS) support through compliance with 802.1p for voice packet prioritization and 802.1q for VLAN
(Layer 2) support
• 802.3af Power over Ethernet
• Dynamic Host Configuration Protocol (DHCP) for IP address conservation within a customer’s LAN
• Session Initiated Protocol (SIP) to support third-party SIP-compliant IP telephones
Benefits of QoS
Networks that are designed to support QoS are best suited for IP deployment since quality of voice is judged by the end-
to-end experience of the user. It is not sufficient for ESI’s IP applications to support QoS if all network components used
in the transport of voice over the customer’s LAN are not properly configured for QoS support.
The benefits of end-to-end QoS in an IP telephony application are many, and when absent, quite noticeable to the user:
• Available bandwidth is optimized by ensuring that voice packets are sent and delivered at a higher priority than “regular” data traffic
on the LAN. This may allow the customer to delay upgrading the speed of transmission of his network. He may be able to defer this
expense until other applications are added or IT changes in the business dictate its necessity.
• The quality of the IP conversation is improved by ensuring that voice packets are delivered and “reassembled” at the other end of
the conversation in order. This eliminates garbled conversation, hollowness, and noticeable gaps in speech.
• Unlike data packets, voice packets cannot be resent if they are dropped. Jitter is reduced for voice packets by QoS. This improves
the likelihood that all voice packets will not be dropped before being delivered at the other end of the IP conversation, as happens
when the amount of jitter of a packet exceeds an acceptable level.
• The latency with which voice packets are delivered is minimized in a network employing QoS. This results in more natural-sounding
speech patterns for both sides of an IP conversation.
Note: Many Internet service providers (ISPs) support QoS only if a service level agreement (SLA) has been obtained.
Capacity constraints
When installed in an ESI Communications Server, an IVC (Intelligent VoIP Card) can be populated with up to 24 48-Key
IP Feature Phone II instruments.
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An ESI Communications Server’s full station capacity can be reached either (a.) with
all extensions installed as IP stations or (b.) when a minimum number of the installed stations are IP instruments (as
shown in the following table).
Config. for full capacity ESI-1000 ESI-600 ESI-200 ESI-100 ESI-50
Card slots used 42 of 42 26 of 28 13 of 14 4 of 4 1 (built-in)
IVCs 29 14 6 3 1 (built-in)
Other cards 13 12 7 1 n/a
IP stations 696 336 144 72 12
Other stations 120 72 48 12 n/a
Note, however, that (except on the ESI-50) the entire system can be configured with only IP stations, by installing only
IVCs. (The quantity of IVCs each system will support varies by system model; see “Facts and figures,” page 2.)
1
Not supported by the ESI-50L.
2
The ESI-50 uses only the G.726 speech compression algorithm and, therefore, can be in an Esi-Link network with only other ESI Communications
Servers set to G.726. ESI’s IVX
®
X-Class and IVX E-Class systems, as well as the original ESI-600 (prior to system software version 16.2.0), use only the
G.729 speech compression algorithm; thus, an ESI-50 cannot be in an Esi-Link network with these systems.
3
Except for the ESI-50. Its main board has a built-in IVC 12 which supports up to 12 IP channels (of which eight can be remote).