Nat Mapping; Quality Of Service; Local Area Network Design - Linksys SPA9000-NA Installation And Configuration Manual

NAT Mapping

Network Address Translation (NAT) is a function that allows multiple devices to share the same public,
routable, IP address to establish connections over the Internet . NAT is present in many broadband
access devices to translate public and private IP addresses . To enable VoIP to co-exist with NAT, some
form of NAT traversal is required .
Some ITSPs provide NAT traversal, but some do not . If your ITSP does not provide NAT traversal, you
have several options .
NAT mapping with SIP-ALG router
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Use a router such as the WRV200, which has a SIP ALG (Application Layer Gateway) . With a SIP ALG
in the router, you have more choices in selecting an ITSP .
ITSP that supports NAT mapping through a Session Border Controller
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With NAT mapping provided by the ITSP, you have more choices in selecting a router .
NAT mapping with the SPA9000 EXT IP setting
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Configuring NAT mapping in the SPA9000 is recommended only if the ITSP network does not
provide a Session Border Controller functionality . In this case, and if the external (public) IP
address is static, then it is recommended to perform a static (permanent) mapping on SPA9000 .
Instructions are available in the LVS Administration Guide .
Configuring NAT Mapping with STUN
•
Configuring NAT mapping in the SPA9000 is recommended only if the ITSP network does not
provide a Session Border Controller functionality . In this case, and if the external (Public) IP
address is assigned dynamically by the network (and the router uses asymmetric NAT mechanism),
it is possible to use STUN as a mechanism to discover the NAT mapping in SPA9000 . This is
considered a practice of last resort and should be used only if the other methods are unavailable .
For more information, see the LVS Administration Guide .

Quality of Service

Linksys recommends using the LVS with QoS-capable networking equipment that can prioritize
the VoIP application traffic . QoS features are available on many Linksys data networking switches
(such as the SLM224P) and routers (such as WRV200) . A QoS-enabled router prioritizes the packets
going upstream to the Internet Service Provider . QoS can be enforced using either DSCP IP TOS
(recommended for its simplified setup) or 802 .1 Q/p VLAN ID and priority setting .
Instructions for the SLM224P are provided in this guide .

Local Area Network Design

Use the following guidelines to manage the LAN setup for the LVS .
Ensure that all LVS components are located in the same local area network subnet .
•
Although all LVS components support static IP addressing, we recommend the use of a DHCP
•
server, as a means to easily add IP telephones to the system . Ensure that the DHCP server
can assign up to enough IP addresses to serve the LVS phones and the existing networked
components such as PCs, servers, and so on .
If using DHCP, use a long lease time . LVS components may reboot on the event of an IP address
•
change because of lease time expiration .
Use stable DNS server addresses for URL name resolution . Your Internet Service Provider can
•
provide the primary and secondary DNS server IP addresses .
Linksys Voice System Installation and Configuration Guide
Preparation
Quality of Service
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