Internet Communications Using SIP : Delivering VoIP and Multimedia Services With Session Initiation Protocol {2Nd Ed.}

DTLS The Datagram TLS(DTLS) [17] transport protocol has been recently standard- ized in the IETF. DTLS adapts the TLS protocol t ...

References [1] “SIP: Session Initiation Protocol” by J. Rosenberg, Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., S ...

[17] “Datagram Transport Layer Security” by E. Rescorla and N. Modadugu. RFC TBD, June 2004. [18] “Session Initiation Protocol ( ...

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173 This chapter will discuss how security devices such as firewalls and network address translators (NATs) can complicate SIP c ...

■■ Modifications to firewalls and NATs so as to make them SIP-aware ■■ NAT and firewall traversal using peer-to-peer (P2P) techn ...

Since SIP was developed, guidelines for protocol design to make them more NAT “friendly” have been developed by the IETF [4]. Un ...

Figure 10.1 Unsuccessful session setup through NAT Of these three problems identified, only this first one has a solution in SIP ...

make the recipient of the successful RTP stream use the received IP address and port number to send RTP, ignoring the IP address ...

Figure 10.2 Unsuccessful call through firewall using UDP Figure 10.3 Unsuccessful call through firewall using TCP If the a UA ou ...

STUN, TURN, and ICE The IETF has standardized three protocols to help assist in NAT traversal. They are Simple Traversal of UDP ...

result, these STUN packets can create bindings in NATs and open pinholes in firewalls, allowing packets to flow in the reverse d ...

Figure 10.4 SIP ALG for firewall traversal The other alternative to an ALG, which proxies both the signaling and media, is to us ...

back to the IP address of the proxy. This Record-Routeheader is forwarded with the request, stored by the UA server, and include ...

For this scenario to work, the UA behind the firewall must have the ALG or firewall proxy set as the default outbound proxy for ...

Summary NAT and firewalls break the SIP signaling and also interfere with the RTP media packet flow between SIP endpoints. The s ...

185 In this chapter, the basic telephony services and features will be discussed as implemented in a SIP-enabled network. First, ...

There are two basic approaches to building these gateways—complete proto- col internetworking and protocol encapsulation. The la ...

Figure 11.1 Gateways, SIP, and PSTN networks To date, neither TRIP nor TGREP has seen any significant deployment or usage by ser ...

in a gateway involves terminating a PCM trunk on the PSTN side and bridg- ing the media with an IP port that sends and receives ...