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A transaction stateful proxy keeps state about a transaction but only for the duration that the request is pending. For EXAMPLE, a transaction stateful proxy would KEEP state when it receives an INVITE request until it received a 200 OK or a final failure response (e.g., 404 Not FOUND). After that, it would destroy the state information. This allows a proxy to PERFORM useful search services but minimize the amount of state storage required.

A transaction stateful proxy keeps state about a transaction but only for the duration that the request is pending. For example, a transaction stateful proxy would keep state when it receives an INVITE request until it received a 200 OK or a final failure response (e.g., 404 Not Found). After that, it would destroy the state information. This allows a proxy to perform useful search services but minimize the amount of state storage required.

A STATELESS proxy server processes each SIP REQUEST or response only based on the MESSAGE contents. Once the message has been PARSED, processed, and forwarded or responded to, no information about the message is stored—no dialog information is stored. A stateless proxy NEVER retransmits a message, and does not use any SIP timers.A stateless proxy never sends a 100 Trying response.

A stateless proxy server processes each SIP request or response only based on the message contents. Once the message has been parsed, processed, and forwarded or responded to, no information about the message is stored—no dialog information is stored. A stateless proxy never retransmits a message, and does not use any SIP timers.A stateless proxy never sends a 100 Trying response.

A stateful proxy server keeps track of requests and responses received in the past and USES that INFORMATION in processing future requests and responses. For example, a stateful proxy server starts a timer when a request is forwarded. If no response to the request is received within the timer period, the proxy will retransmit the request, RELIEVING the USER agent of this task. A stateful proxy usually sends a 100 Trying response when it RECEIVES an INVITE.

A stateful proxy server keeps track of requests and responses received in the past and uses that information in processing future requests and responses. For example, a stateful proxy server starts a timer when a request is forwarded. If no response to the request is received within the timer period, the proxy will retransmit the request, relieving the user agent of this task. A stateful proxy usually sends a 100 Trying response when it receives an INVITE.

A SIP proxy server sits in the MIDDLE of SIP message exchange, receives messages and forwards them, but it does not set up or terminate sessions. A proxy server typically has access to a DATABASE or a location SERVICE to aid it in processing the request (determining the next hop). Databases could contain SIP registrations, presence information, or any other type of information about where a user is located.

A SIP proxy server sits in the middle of SIP message exchange, receives messages and forwards them, but it does not set up or terminate sessions. A proxy server typically has access to a database or a location service to aid it in processing the request (determining the next hop). Databases could contain SIP registrations, presence information, or any other type of information about where a user is located.

SIP URI is a name that is resolved to an IP address by using SIP proxy SERVER and DNS LOOKUPS at the time of the CALL.

SIP URI is a name that is resolved to an IP address by using SIP proxy server and DNS lookups at the time of the call.

A REQUEST routed using only IP addresses will reach only one end point—only one device. Since communication is typically user-to-user INSTEAD of device-to-device, a more useful addressing scheme would allow a particular user to call another particular user, which would result in the request REACHING the target user regardless of which he is currently using, or if he has multiple devices.SIP URI is a name that is resolved to an IP ADDRESS by using SIP proxy server and DNS lookups at the time of the call.

A request routed using only IP addresses will reach only one end point—only one device. Since communication is typically user-to-user instead of device-to-device, a more useful addressing scheme would allow a particular user to call another particular user, which would result in the request reaching the target user regardless of which he is currently using, or if he has multiple devices.SIP URI is a name that is resolved to an IP address by using SIP proxy server and DNS lookups at the time of the call.

Outside the dialog MEANS that it is not within the context of a dialog. It DOESNT USE the callid, cseq, or route SETS of any existing DIALOGS, and when such a reuqest is set, it has no impact on the state of an existing dialog.

Outside the dialog means that it is not within the context of a dialog. It doesnt use the callid, cseq, or route sets of any existing dialogs, and when such a reuqest is set, it has no impact on the state of an existing dialog.

Dialog represents STATE, which includes sequence NUMBERS, route sets, and URIs. A request sent as part of a dialog means that it includes route HEADERS from the route set of the dialog, and USES the next highest sequence NUMBER in the dialog.

Dialog represents state, which includes sequence numbers, route sets, and URIs. A request sent as part of a dialog means that it includes route headers from the route set of the dialog, and uses the next highest sequence number in the dialog.

A dialog is a sip RELATIONSHIP. A SESSION is a media relationship. Dialog MEAN a "call has already been setup" in the signaling sense, while a session mean the "media has already been setup" in the media sense.

A dialog is a sip relationship. A session is a media relationship. Dialog mean a "call has already been setup" in the signaling sense, while a session mean the "media has already been setup" in the media sense.

No, because BYE MESSAGE is CONSIDERED as a NEW TRANSACTION.

No, because BYE message is considered as a new transaction.

No, branch PARAMETER in Via HEADER FIELD of the ACK would be different than the INVITE message of that session because ACK SENT to acknowledge the 200OK is considered as a seperate transaction.

No, branch parameter in Via header field of the ACK would be different than the INVITE message of that session because ACK sent to acknowledge the 200OK is considered as a seperate transaction.

No, the To and From HEADER FIELDS in SIP are defined to indicate the direction of the request, not the direction of the MESSAGE.

No, the To and From header fields in SIP are defined to indicate the direction of the request, not the direction of the message.

Usually the RECEIVED parameter can be found in Via header field of the RESPONSE message. This parameter CONTAINS the literal IP address that the request was received from, which typically is the same address that the URI in the Via RESOLVES using DNS.

Usually the received parameter can be found in Via header field of the response message. This parameter contains the literal IP address that the request was received from, which typically is the same address that the URI in the Via resolves using DNS.

CONTACT header field contains the device-URI where the originator of REQUEST or response can be DIRECTLY reached. Usually contains IP address of the device which generated the request or response.

Contact header field contains the device-URI where the originator of request or response can be directly reached. Usually contains IP address of the device which generated the request or response.

VIA, Max-Forwards, To, From, Call-ID and CSeq are the MINIMUM REQUIRED HEADER FIELDS.

Via, Max-Forwards, To, From, Call-ID and CSeq are the minimum required header fields.

CSeq or Command SEQUENCE contains a NUMBER FOLLOWED by METHOD name.This number is incremented for each new request sent.

CSeq or Command Sequence contains a number followed by method name.This number is incremented for each new request sent.

The combination of the local tag (contained in the From header FIELD), remote tag (contained in the To header field), and the Call-ID UNIQUELY IDENTIFIES the established session, known as a “DIALOG.” This dialog IDENTIFIER is used by both parties to identify this call because they could have multiple calls set up between them. Subsequent requests within the established session will use this dialog identifier.

The combination of the local tag (contained in the From header field), remote tag (contained in the To header field), and the Call-ID uniquely identifies the established session, known as a “dialog.” This dialog identifier is used by both parties to identify this call because they could have multiple calls set up between them. Subsequent requests within the established session will use this dialog identifier.

The CALL-ID HEADER FIELD is an identifier used to keep track of a particular SIP session. The originator of the request creates a locally UNIQUE string, then usually adds an “@” and its host name to make it globally unique. In addition to the Call-ID, each party in the session also contributes a random identifier, unique for each call. These identifiers, called tags, are included in the To and From header FIELDS as the session is established. The user agent that generates the initial INVITE to establish the session generates the unique Call-ID and From tag. In the response to the INVITE, the user agent answering the request will generate the To tag. The combination of the local tag (contained in the From header field), remote tag (contained in the To header field), and the Call-ID uniquely identifies the established session, known as a “dialog.” This dialog identifier is used by both parties to identify this call because they could have multiple calls set up between them. Subsequent requests within the established session will use this dialog identifier.

The Call-ID header field is an identifier used to keep track of a particular SIP session. The originator of the request creates a locally unique string, then usually adds an “@” and its host name to make it globally unique. In addition to the Call-ID, each party in the session also contributes a random identifier, unique for each call. These identifiers, called tags, are included in the To and From header fields as the session is established. The user agent that generates the initial INVITE to establish the session generates the unique Call-ID and From tag. In the response to the INVITE, the user agent answering the request will generate the To tag. The combination of the local tag (contained in the From header field), remote tag (contained in the To header field), and the Call-ID uniquely identifies the established session, known as a “dialog.” This dialog identifier is used by both parties to identify this call because they could have multiple calls set up between them. Subsequent requests within the established session will use this dialog identifier.

When a name LABEL is used, the SIP URI is ENCLOSED in brackets and used for routing the request.The name label could be displayed during alerting, but is not used by the PROTOCOL.

When a name label is used, the SIP URI is enclosed in brackets and used for routing the request.The name label could be displayed during alerting, but is not used by the protocol.

To and From header fields SHOW the ORIGINATOR and destination of the SIP REQUEST.

To and From header fields show the originator and destination of the SIP request.

Max-Forwards HEADER field is used for simple LOOP DETECTION. It is initialized to some large integer and decremented by each SIP SERVER which receives and forwards the request.

Max-Forwards header field is used for simple loop detection. It is initialized to some large integer and decremented by each SIP server which receives and forwards the request.

A "BRANCH" parameter is used in "Via" header field. It is SIGNIFIED as the TRANSACTION identifier used to correlate the REPONSES to the REQUEST.

A "branch" parameter is used in "Via" header field. It is signified as the transaction identifier used to correlate the reponses to the request.

Each SIP device that originates or forwards a SIP message stamps its own address in a "Via" header field, usually written as a HOST name that can be resolved into an IP address using a DNS QUERY. The Via header field CONTAINS the SIP version number (2.0), a “/”, then UDP for UDP transport, a SPACE, then the hostname or address, a COLON, then a port number. And also contain "branch" parameter.

Each SIP device that originates or forwards a SIP message stamps its own address in a "Via" header field, usually written as a host name that can be resolved into an IP address using a DNS query. The Via header field contains the SIP version number (2.0), a “/”, then UDP for UDP transport, a space, then the hostname or address, a colon, then a port number. And also contain "branch" parameter.

The Request-URI is a special FORM of SIP URI and indicates the resource to which the request is being sent, ALSO known as the request target.

The Request-URI is a special form of SIP URI and indicates the resource to which the request is being sent, also known as the request target.

The Session Initiation Protocol (SIP) is a signaling, PRESENCE and instant messaging protocol developed to SET up, MODIFY, and tear down multimedia sessions, request and deliver presence and instant MESSAGES over the Internet. SIP is a text-encoded protocol.

The Session Initiation Protocol (SIP) is a signaling, presence and instant messaging protocol developed to set up, modify, and tear down multimedia sessions, request and deliver presence and instant messages over the Internet. SIP is a text-encoded protocol.