ViaHeader (jain-sip-ri 1.2.226 API)

All Superinterfaces:

Cloneable, Header, Parameters, Serializable

All Known Subinterfaces:

ViaHeaderExt

All Known Implementing Classes:

Via
```
public interface ViaHeader
extends Parameters, Header
```
The Via header field indicates the transport used for the transaction and identifies the location where the response is to be sent. A Via header field value is added only after the transport that will be used to reach the next hop has been selected. When the UAC creates a request, it MUST insert a Via into that request. The protocol name and protocol version in the header field MUST be SIP and 2.0, respectively. The Via header field value MUST contain a branch parameter. This parameter is used to identify the transaction created by that request. This parameter is used by both the client and the server.
Branch Parameter:
The branch parameter value MUST be unique across space and time for all requests sent by the User Agent. The exceptions to this rule are CANCEL and ACK for non-2xx responses. A CANCEL request will have the same value of the branch parameter as the request it cancels. An ACK for a non-2xx response will also have the same branch ID as the INVITE whose response it acknowledges.
The uniqueness property of the branch ID parameter, to facilitate its use as a transaction ID, was not part of RFC 2543. The branch ID inserted by an element compliant with this specification MUST always begin with the characters "z9hG4bK". These 7 characters are used as a magic cookie (7 is deemed sufficient to ensure that an older RFC 2543 implementation would not pick such a value), so that servers receiving the request can determine that the branch ID was constructed in the fashion described by this specification (that is, globally unique). Beyond this requirement, the precise format of the branch token is implementation-defined. JSIP defines a convenience function to generate unique branch identifiers at Transaction.getBranchId()
A common way to create the branch value is to compute a cryptographic hash of the To tag, From tag, Call-ID header field, the Request-URI of the request received (before translation), the topmost Via header, and the sequence number from the CSeq header field, in addition to any Proxy-Require and Proxy-Authorization header fields that may be present. The algorithm used to compute the hash is implementation-dependent.
Via Processing Rules
- Generating Requests (UAC): The client originating the Request must insert into the Request a ViaHeader containing its host name or network address and, if not the default port number, the port number at which it wishes to receive Responses. (Note that this port number can differ from the UDP source port number of the Request.) A fully-qualified domain name is recommended.
- Request Forwarding by Proxies: The proxy MUST insert a Via header field value into the copy before the existing Via header field values. This implies that the proxy will compute its own branch parameter, which will be globally unique for that branch, and contain the requisite magic cookie. Note that this implies that the branch parameter will be different for different instances of a spiraled or looped request through a proxy. If a proxy server receives a Request which contains its own address in a ViaHeader, it must respond with a 482 (Loop Detected) Response. A proxy server must not forward a Request to a multicast group which already appears in any of the ViaHeaders. This prevents a malfunctioning proxy server from causing loops. Also, it cannot be guaranteed that a proxy server can always detect that the address returned by a location service refers to a host listed in the ViaHeader list, as a single host may have aliases or several network interfaces.
- Response processing by UAC and proxies:
  - The first ViaHeader should indicate the proxy or client processing this Response. If it does not, discard the Response. Otherwise, remove this ViaHeader.
  - If there is no second ViaHeader, this Response is destined for this client. Otherwise, the processing depends on whether the ViaHeader contains a maddr parameter or is a receiver-tagged field.
  - If the second ViaHeader contains a maddr parameter, send the Response to the multicast address listed there, using the port indicated in "sent-by", or port 5060 if none is present. The Response should be sent using the TTL indicated in the ttl parameter, or with a TTL of 1 if that parameter is not present. For robustness, Responses must be sent to the address indicated in the maddr parameter even if it is not a multicast address.
  - If the second ViaHeader does not contain a maddr parameter and is a receiver-tagged ViaHeader, send the Response to the address in the received parameter, using the port indicated in the port value, or using port 5060 if none is present.
  - If neither of the previous cases apply, send the Response to the address indicated by the host value in the second ViaHeader.
- Sending Responses (UAS):
  - If the first ViaHeader in the Request contains a maddr parameter, send the Response to the multicast address listed there, using the port indicated, or port 5060 if none is present. The Response should be sent using the TTL indicated in the ttl parameter, or with a TTL of 1 if that parameter is not present. For robustness, Responses must be sent to the address indicated in the maddr parameter even if it is not a multicast address.
  - If the address in the first ViaHeader differs from the source address of the packet, send the Response to the actual packet source address, similar to the treatment for receiver-tagged ViaHeaders.
  - If neither of these conditions is true, send the Response to the address contained in the host value. If the Request was sent using TCP, use the existing TCP connection if available.
Via Parameters: A Via header field value contains the transport protocol used to send the message, the client's host name or network address, and possibly the port number at which it wishes to receive responses. Transport protocols defined here are "UDP", "TCP", "TLS", and "SCTP". "TLS" means TLS over TCP. When a request is sent to a SIPS URI, the protocol still indicates "SIP", and the transport protocol is TLS. A Via header field value can also contain parameters such as "maddr", "ttl", "received", and "branch". A proxy sending a Request to a multicast address must add the maddr parameter to its ViaHeader, and should add the ttl parameter. If a server receives a Request which contained an maddr parameter in the topmost ViaHeader, it should send the Response to the multicast address listed in the maddr parameter. The received parameter is added only for receiver-added ViaHeaders.
Two Via header fields are equal if their sent-protocol and sent-by fields (including port) are equal, both have the same set of parameters, and the values of all parameters are equal.
Version:

1.2

Author:

BEA Systems, NIST

Field Summary

Fields
Modifier and Type Field and Description

static String NAME
Name of ViaHeader

Fields
Modifier and Type	Field and Description
`static String`	`NAME` Name of ViaHeader

Method Summary

Methods
Modifier and Type	Method and Description
`boolean`	`equals(Object obj)` Compare this ViaHeader for equality with another.
`String`	`getBranch()` Gets the branch paramater of the ViaHeader.
`String`	`getHost()` Returns the host part of this ViaHeader.
`String`	`getMAddr()` Returns the value of the `maddr` parameter, or null if this is not set.
`int`	`getPort()` Returns the port part of this ViaHeader.
`String`	`getProtocol()` Returns the value of the protocol used.
`String`	`getReceived()` Gets the received paramater of the ViaHeader.
`int`	`getRPort()` Returns the rport part of this ViaHeader.
`String`	`getTransport()` Returns the value of the transport parameter.
`int`	`getTTL()` Returns the value of the ttl parameter, or -1 if this is not set.
`void`	`setBranch(String branch)` Sets the branch parameter of the ViaHeader to the newly supplied branch value.
`void`	`setHost(String host)` Set the host part of this ViaHeader to the newly supplied `host` parameter.
`void`	`setMAddr(String mAddr)` Sets the value of the `maddr` parameter of this ViaHeader.
`void`	`setPort(int port)` Set the port part of this ViaHeader to the newly supplied `port` parameter.
`void`	`setProtocol(String protocol)` Sets the value of the protocol parameter.
`void`	`setReceived(String received)` Sets the received parameter of ViaHeader.
`void`	`setRPort()` Set the rport part of this ViaHeader.
`void`	`setTransport(String transport)` Sets the value of the transport.
`void`	`setTTL(int ttl)` Sets the value of the ttl parameter.

Methods inherited from interface android.javax.sip.header.Parameters
getParameter, getParameterNames, removeParameter, setParameter

Methods inherited from interface android.javax.sip.header.Header
clone, getName, hashCode, toString

- Field Detail
  - NAME
```
static final String NAME
```
    Name of ViaHeader
    
    See Also:
    Constant Field Values
- Method Detail
  - setHost
```
void setHost(String host)
             throws ParseException
```
    Set the host part of this ViaHeader to the newly supplied host parameter.
    
    Parameters:
    host - - the new value of the host of this ViaHeader
    
    Throws:
    
    ParseException - which signals that an error has been reached unexpectedly while parsing the host value.
  - getHost
```
String getHost()
```
    Returns the host part of this ViaHeader.
    
    Returns:
    the string value of the host
  - setPort
```
void setPort(int port)
             throws InvalidArgumentException
```
    Set the port part of this ViaHeader to the newly supplied port parameter.
    
    Parameters:
    port - - the new integer value of the port of this ViaHeader
    
    Throws:
    
    InvalidArgumentException - when the port value is not -1 and <1 or >65535
  - getPort
```
int getPort()
```
    Returns the port part of this ViaHeader.
    
    Returns:
    the integer value of the port, -1 if not present
  - getTransport
```
String getTransport()
```
    Returns the value of the transport parameter.
    
    Returns:
    the string value of the transport paramter of the ViaHeader
  - setTransport
```
void setTransport(String transport)
                  throws ParseException
```
    Sets the value of the transport. This parameter specifies which transport protocol to use for sending requests and responses to this entity. The following values are defined: "udp", "tcp", "sctp", "tls", but other values may be used also.
    
    Parameters:
    transport - - new value for the transport parameter
    
    Throws:
    
    ParseException - which signals that an error has been reached unexpectedly while parsing the transport value.
  - getProtocol
```
String getProtocol()
```
    Returns the value of the protocol used.
    
    Returns:
    the string value of the protocol paramter of the ViaHeader
  - setProtocol
```
void setProtocol(String protocol)
                 throws ParseException
```
    Sets the value of the protocol parameter. This parameter specifies which protocol is used, for example "SIP/2.0".
    
    Parameters:
    protocol - - new value for the protocol parameter
    
    Throws:
    
    ParseException - which signals that an error has been reached unexpectedly while parsing the protocol value.
  - getTTL
```
int getTTL()
```
    Returns the value of the ttl parameter, or -1 if this is not set.
    
    Returns:
    the integer value of the ttl parameter
  - setTTL
```
void setTTL(int ttl)
            throws InvalidArgumentException
```
    Sets the value of the ttl parameter. The ttl parameter specifies the time-to-live value when packets are sent using UDP multicast.
    
    Parameters:
    ttl - - new value of the ttl parameter
    
    Throws:
    
    InvalidArgumentException - if supplied value is less than zero or greater than 255, excluding -1 the default not set value.
  - getMAddr
```
String getMAddr()
```
    Returns the value of the maddr parameter, or null if this is not set.
    
    Returns:
    the string value of the maddr parameter
  - setMAddr
```
void setMAddr(String mAddr)
              throws ParseException
```
    Sets the value of the maddr parameter of this ViaHeader. The maddr parameter indicates the server address to be contacted for this user, overriding any address derived from the host field.
    
    Parameters:
    mAddr - new value of the mAddr parameter
    
    Throws:
    
    ParseException - which signals that an error has been reached unexpectedly while parsing the mAddr value.
  - getReceived
```
String getReceived()
```
    Gets the received paramater of the ViaHeader. Returns null if received does not exist.
    
    Returns:
    the string received value of ViaHeader
  - setReceived
```
void setReceived(String received)
                 throws ParseException
```
    Sets the received parameter of ViaHeader.
    
    Parameters:
    received - - the newly supplied received parameter.
    
    Throws:
    
    ParseException - which signals that an error has been reached unexpectedly while parsing the received value.
  - getBranch
```
String getBranch()
```
    Gets the branch paramater of the ViaHeader. Returns null if branch does not exist.
    
    Returns:
    the string branch value of ViaHeader
  - setBranch
```
void setBranch(String branch)
               throws ParseException
```
    Sets the branch parameter of the ViaHeader to the newly supplied branch value. Note that when sending a Request within a transaction, branch id management will be the responsibility of the SipProvider; that is the application should not set this value. This method should only be used by the application when sending Requests outside of a transaction.
    
    Parameters:
    branch - - the new string branch parmameter of the ViaHeader.
    
    Throws:
    
    ParseException - which signals that an error has been reached unexpectedly while parsing the branch value.
  - setRPort
```
void setRPort()
              throws InvalidArgumentException
```
    Set the rport part of this ViaHeader. This method indicates to the remote party that you want it to use rport. It is the applications responsisbility to call this method to inform the implementation to set the value of the rport. This allows a client to request that the server send the response back to the source IP address and port from which the request originated. See RFC3581
    
    Throws:
    
    InvalidArgumentException - if rport value is an illegal integer ( <=0 ).
    Since:
    
    v1.2
  - getRPort
```
int getRPort()
```
    Returns the rport part of this ViaHeader.
    
    Returns:
    the integer value of the rport or -1 if the rport parameter is not set.
    Since:
    
    v1.2
  - equals
```
boolean equals(Object obj)
```
    Compare this ViaHeader for equality with another. This method overrides the equals method in android.javax.sip.Header. This method specifies object equality as outlined by RFC3261. Two Via header fields are equal if their sent-protocol and sent-by fields are equal, both have the same set of parameters, and the values of all parameters are equal. When comparing header fields, field names are always case-insensitive. Unless otherwise stated in the definition of a particular header field, field values, parameter names, and parameter values are case-insensitive. Tokens are always case-insensitive. Unless specified otherwise, values expressed as quoted strings are case-sensitive.
    
    Specified by:
    
    equals in interface Header
    
    Overrides:
    
    equals in class Object
    
    Parameters:
    obj - the object to compare this ViaHeader with.
    
    Returns:
    true if obj is an instance of this class representing the same ViaHeader as this, false otherwise.
    Since:
    
    v1.2

Interface ViaHeader

Field Summary

Method Summary

Methods inherited from interface android.javax.sip.header.Parameters

Methods inherited from interface android.javax.sip.header.Header

Field Detail

NAME

Method Detail

setHost

getHost

setPort

getPort

getTransport

setTransport

getProtocol

setProtocol

getTTL

setTTL

getMAddr

setMAddr

getReceived

setReceived

getBranch

setBranch

setRPort

getRPort

equals