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signaling protocol that controls the initiation, modification, and termination of interactive multimedia sessions
text-based protocol
peer-to-peer protocol,
Session Initiation Protocol (SIP)
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call routing and session management functions are distributed across all the nodes (including endpoints
and network servers)
Session Initiation Protocol (SIP)
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In June 2002, the IETF published a new SIP RFC
RFC 3261
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provides the capability to discover the location of the end user for the purpose of establishing a session or delivering a SIP request
user location
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enables the determination of the media capabilities of the devices that are involved in the session.
User Capabilities
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willingness of the end user to engage in communication.
User Availability
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enables the establishment of session parameters for the parties who are involved in the session.
session setup
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enables the modification, transfer, and termination of an active session.
session handeling
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is responsible for forwarding SIP requests to the target UAS
provides routing infromation
enforce security policy
proxy
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for reserving network resources
Resource Reservation Protocol (RSVP)
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for gateway selection and load balancing
Telephony Routing over IP (TRIP)
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for hostname-to-IP address resolution
Domain Name System (DNS)
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for preventing eavesdropping, tampering, or message forgery.
Transport Layer Security (TLS)
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to resolve host or domain names into routable IP addresses
used to load-share across multiple servers in a cluster identified by a hostname
DNS
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to describe the parameters of the multimedia session. This information includes session type such as audio, video, or both and parameters such as codecs or ports needed to establish a media stream.
Session Description Protocol (SDP)
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transports real-time data such as audio or video packets to the endpoints that are involved in a session
Realtime Transport Protocol (RTP)
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encryption technology can cause what
delay
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to reserve network resources such as bandwidth prior to establishment of the media session. This ensures that the network resources are in place prior to the called party
RSVP
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to provide privacy and integrity of SIP signaling information over the network
TLS
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protocol to discover the presence and type of Network Address Translation (NAT) between them and the
public Internet.
STUN
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signaling is independent of the type of session being established
SIP
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can send calls to the pstn
sip gateway
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in sip network the telephone picking up the call is the
server
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is typically an e-mail-type address with a format such as one of the following: sip:user@domain:port sip:user@host:port
SIP URI
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identify a user or a resource within a network domain
SIP address
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are messages that are sent from client to server to invoke a SIP operation
SIP Request
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indicates that the recipient user or service is invited to participate in a session
"placing a call"
Invite
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that the UAC has received the final response to an INVITE request.
ACK
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to query a UAS about its capabilities
options
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**request the termination of a previously established session**
bye
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*hang up a call be befor the user picked up *
cancle
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email address be corsponed to an ip address
register
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sent from the server to client
1xx provisional status
numbered from 100 to 699
SIP Response Messages
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establishment of the session
defined as a peer-to-peer
SIP relationship between two or more UAs that persists for the duration of the session
dialog
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uses TCP, Stream Control Transmission Protocol (SCTP) and UDP
SIP transport layer
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the SIP RFC 3261 encrypt the signaling information what 2
TLS IPsec
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my drop out or stay in the call while it take place
SIP proxy server
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proxy sends a message back to the user say that the user has moved
redirect
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starts at the server not the phone
only involved in call set up
can initiate new SIP calls and modify and terminate existing calls.
creation of two distinct dialogs, which enable it to modify one SIP session without affecting the other
session.
act as a third-party call controller (3PCC) and can establish calls between two user agents.
B2BUA(Back-to-back user agent)
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To determine the address of SIP servers that support UDP transport in company.com domain, you need to
query a What ? with the DNS server
query string
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to determine what services are supported in a domain
Naming Authority Pointer (NAPTR)
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the services and protocols that are supported within the domain.
Service Record (SRV)
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registrar and proxy are functions implemented with the
same server
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sip proxies router SIP request to the server and sip resoponces to the
client
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client insists that the server must understnd the SIP extension to process a request
Require header
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indication to the UAS(server) that the UAC(client) understands a certain extension
supported header
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SIP extension that enables a caller to express his preferences about request handling at the intermediate
servers.
Caller and Callee Preferences
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which SIP nodes can request notification from remote peers when monitored events take place
(voice mail messafe changing online status)
SUBSCRIBE and NOTIFY
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is waiting for the end-user input to determine whether to accept a subscription from this subscriber.
Subscription-State value is pending in the NOTIFY request
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near real time mesafes but the person must be willing to engage in the session
Instant Message (IM)
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enables users to publish their availability status and display messages or icons as a form of self-expression
presence
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MESSAGE requests carry the message content in the form of
MIME
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an IETF signaling protocol for multimedia applications involving one or more participants
SIP
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a flexible protocol that supports extensions for new applications and services
SIP
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SIP dialog state is maintained at the
endpoints
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SIP network servers are either stateless or maintain transaction state information for at least
32 sec
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