英语翻译SIP messages are encoded using HTTP/1.1 message syntax [6],and the content of each message follows sessiondescription protocol (SDP) [7],heavily used in the context of MBONE for distributing information about MBONEsessions.In addition to

英语翻译SIP messages are encoded using HTTP/1.1 message syntax [6],and the content of each message follows sessiondescription protocol (SDP) [7],heavily used in the context of MBONE for distributing information about MBONEsessions.In addition to
英语翻译
SIP messages are encoded using HTTP/1.1 message syntax [6],and the content of each message follows session
description protocol (SDP) [7],heavily used in the context of MBONE for distributing information about MBONE
sessions.
In addition to SIP terminals which represent an IP telephones or Gateways,SIP architecture is based on four different
servers entities:
· Proxy server,which forwards requests to its final destination.Like the Gatekeeper in H.323 model,it
receives requests and sends them to the appropriate destination.In this case the Via field in the
request/response message indicates the intermediate proxies which participate in the request process.This
avoids routing loops as well as permits to force the responses to follow the same route back.Proxy servers
do not need to relay the media except in case of transcoding operations (they only need to relay control
information).
· Redirect Server,which,on the contrary to proxies,does not forward INVITE requests but responds to
clients with a redirection message that informs about the next hop.
Registrar server,that keeps track of the current location of a user by accepting registration request
messages.Registrar server are discovered by using well-known multicast addresses or preconfigured unicast
addresses.
· Call Agent,which is a service that handles incoming and outgoing calls on behalf of a user.It is a mixture of
a proxy,a registrar and a redirect server.A call agent can perform tasks like:
Try to find a user by redirecting the call setup message to the proper location or locations.
Implement call redirection rules such as call forwarding on busy,call forward on no answer,etc.
Implement call filtering with origin/time-dependant rules.
Record unsuccessful call attempts for future reference.
Perform any other call management task on behalf of the user.

英语翻译SIP messages are encoded using HTTP/1.1 message syntax [6],and the content of each message follows sessiondescription protocol (SDP) [7],heavily used in the context of MBONE for distributing information about MBONEsessions.In addition to
经我仔细检查过.相信你应该很满意的~
啜饮消息被使用HTTP / 1.1 消息句法把进行编码 [6],并且每条消息的内容跟随会议
说明协议(SDP) [7],鉴于MBONE 为分配关于MBONE的信息重使用
会议.
除描述一部IP电话或者通道的啜饮终端之外,啜饮建筑基于4 不同
服务器实体：
· 代理服务器,寄请求到它的最后的目的地.象用H.的看门人323 模型,它一样
收到请求并且把它们送到合适的目的地.这样的话通过领域在方面
请求/应答信息表明代理人那些媒体参加那些过程请求.这
避免循环路由和迫使反应向后跟随相同的路线的许可证.代理服务器
不需要转播媒介除transcoding 经营之外(他们只需要转播控制
信息).
· 使服务器,改方向,关于个与代理人,母鹿相反不寄的邀请请求但是对作出反应
有通知大约下一个航程的一条改向消息的客户.
注册员服务器,跟踪为接受登记现行存储单元一个用户请求
消息.注册员服务器通过使用著名的多路传送地址或者preconfigured 单播被发现
地址.
· 叫代理人,这是代表一个用户处理输入和输出电话的一种服务.一混合物
一个代理人,一个注册员和一更改服务器.一位电话代理人能执行任务类似人或物：
试试通过把电话安装消息使到适当的位置或者位置改方向找到一个用户.
执行在忙上的例如电话寄叫改寄规章,在答案不上向前叫,等等
实现打电话给有起源/时间过滤从属人的规章.
不成功的电话以作日后参考试图做的记录.
代表用户进行任何其他电话管理工作.