會談邊界控制器

會談邊界控制器（Session Border Controller, SBC），一種NAT穿透的方式。SBC可確保VoIP 安全，又可提供媒體代理伺服器的套件。

SBC架構於IMS網路之上，可作為IMS網路的SIP和RTSP的 Proxy Server，所有的SIP與RTSP訊息都會透過SBC來處理，SBC更具備NAT穿透的功能。

功能
SBCs 會維持整個會議狀態並提供以下功能:

• 网络安全 – 保護網路以及其他裝置:

:* Malicious 攻擊, 像是分散式阻斷服務攻擊 (DoS) 或是分散式 DoS
:* Toll fraud via rogue media streams
:* 拓樸隱藏（Topology hiding）
:* Malformed packet protection
:* 訊號加密 (經由 TLS 以及 IPSec) 以及媒體 (SRTP)

• 連結 – 允許不同網域之間的溝通:

:* NAT 穿透
:* SIP 正規化 via SIP message and header manipulation
:* IPv4 轉 IPv6
:* VPN 連結
:* 協定轉換, 如 SIP, SIP-I, H.323

• 服务质量 – QoS 的政策是網路狀態的優先取捨問題. 其功能如下:

:* Traffic policing
:* Resource allocation
:* Rate limiting
:* Call admission control
:* TOS/DSCP bit setting

• Regulatory – many times the SBC is expected to provide support for regulatory requirements such as:

:* emergency calls prioritization and
:* lawful interception

• Media services – many of the new generation of SBCs also provide built-in digital signal processors (DSPs) to enable them to offer border-based media control and services such as:

:* DTMF 中繼與互連
:* 媒體轉碼
:* Tones 與 announcements
:* 數據與內網傳真
:* 支援音訊與影訊

• 統計與傳單資訊 – since all sessions that pass through the edge of the network pass through the SBC, it is a natural point to gather statistics and usage based information on these sessions.

參考書目
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• Sonus Networks [https://web.archive.org/web/20120123221159/http://sonusnet.com/content/whitepaper-details/The-Performance-Reality-of-Session-Border-Controllers-/16.aspx WhitePaper] — Performance reality of Session Border Controllers
• Acme Packet [http://www.acmepacket.com/images/whitepaper_SBC.pdf White Paper] — defines the need for session border controllers for interactive IP services
• AudioCodes [https://web.archive.org/web/20111227125901/http://www.audiocodes.com/e-sbc White Paper] — on Enterprise Session Border Controllers.

參見

• IP多媒體子系統
• LTE
• UMTS