R2511-HP MSR Router Series Voice Configuration Guide(V5)

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TLS-SRTP combinations
TLS protects control signaling, and SRTP encrypts and authenticates voice media flows. You can use them
separately or together. As shown in Table 15, ther
e are four combinations of TLS and SRTP.
Table 15 TLS-SRTP combinations
TLS SRTP Descri
p
tion
On On
Signaling packets are secured. Personal information is protected.
Media packets are secured. Call conversations are protected.
Recommended.
Off On
Signaling packets are not secured. Personal information is not protected.
Media packets are secured. Call conversations are protected.
On Off
Signaling packets are secured. Personal information is protected.
Media packets are not secured. Call conversations are not protected.
Off Off
Signaling packets are not secured. Personal information is not protected.
Media packets are not secured. Call conversations are not protected.
Support for basic QSIG call
As shown in Figure 40, the two ISDN networks connected through a SIP network need to communicate
with each other by using QSIG signaling. To support this application, the voice gateways Router A and
B need to translate between QSIG and SIP signaling messages. However, this type of gateways can only
translate basic call signaling rather than a great amount of QSIG signaling related to supplementary
services. To solve this problem, a method of encapsulating original QSIG signaling messages within SIP
messages was introduced to tunnel ISDN signaling over a SIP network. This method is called SIP for
telephones (SIP-T).
Figure 40 Tunneling QSIG signaling messages over a SIP network
The core of the STP-T protocol is to encapsulate and decapsulate ISDN messages. The ingress gateway
encapsulates QSIG signaling messages received from a sender into SIP messages, and sends them to the
egress gateway. Upon receiving SIP messages, the egress gateway extracts the QSIG signaling
messages from the SIP messages and sends them to the receiving end.
Compared with the simple mapping between QSIG signaling and SIP signaling, the SIP-T protocol
enhances the mapping between the two signaling protocols by improving the integrity and abundance
of the ISDN signaling contents. This enables the lossless transmission of ISDN signaling over the SIP
network between two ISDN networks.