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Cisco SIP IP Phone Administrator Guide
Chapter 1 Product Overview
What Is the Cisco SIP IP Phone?
Supported Protocols
The Cisco SIP IP phone supports the following standard protocols:
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Domain Name System (DNS)—Used in the Internet for translating names of network nodes into
addresses. SIP uses DNS to resolve the host names of endpoints to IP addresses.
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Dynamic Host Control Protocol (DHCP)—Used to dynamically allocate and assign IP addresses.
DHCP allows you to move network devices from one subnet to another without administrative
attention. If using DHCP, you can connect Cisco SIP IP phones to the network and become
operational without having to manually assign an IP address and additional network parameters.
The Cisco SIP IP phone complies with the DHCP specifications documented in RFC 2131. By
default, Cisco SIP IP phones are DHCP-enabled.
•
Internet Control Message Protocol (ICMP)—A network layer Internet protocol that enables hosts to
send error or control messages to other hosts. ICMP also provides other information relevant to IP
packet processing.
The Cisco SIP supports ICMP as it is documented in RFC 792.
•
Internet Protocol (IP)—A network layer protocol that sends datagram packets between nodes on the
Internet. IP also provides features for addressing, type-of-service (ToS) specification, fragmentation
and reassembly, and security.
The Cisco SIP IP phone supports IP as it is defined in RFC 791.
•
Real-Time Transport Protocol (RTP)—Transports real-time data (such as voice data) over data
networks. RTP also has the ability to obtain quality of service (QoS) information.
The Cisco SIP IP phone supports RTP as a media channel.
•
Session Description Protocol (SDP)—An ASCII-based protocol that describes multimedia sessions
and their related scheduling information.
The Cisco SIP IP phone uses SDP for session description.
•
Simple Network Time Protocol (SNTP)—Sychronizes computer clocks on an IP network. The
Cisco SIP IP phones use SNTP for their date and time support.
•
Transmission Control Protocol (TCP)—Provides a reliable byte-stream transfer service between two
endpoints on an internet. The Cisco SIP IP phone supports TCP for Telnet sessions only.
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Trivial File Transfer Protocol (TFTP)—Allows files to be transferred from one computer to another
over a network. The Cisco SIP IP phone uses TFTP to download configuration files and software
updates.
•
User Datagram Protocol (UDP)—A simple protocol that exchanges data packets without
acknowledgments or guaranteed delivery. SIP can use UDP as the underlying transport protocol. If
UDP is used, retransmissions are used to ensure reliability.
The Cisco SIP IP phone supports UDP as it is defined in RFC 768 for SIP signaling.
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Hypertext Transfer Protocol (HTTP)—The phone contains limited support for HTTP 1.1. The
phone uses HTTP to retrieve Cisco CallManager XML files.
