在SIP中实现RSVP功能

在SIP中实现RSVP的步骤如图3-9所示。 

        图3-9中实线的部分是SIP命令，虚线部分是RSVP消息。首先创建一个RSVP的会话萸 例，如果成功则返回一个非零的数值用于表示建立的会话ID号，创建会话是为了发送RSVP PATH或者是发送RSVP RESVo接下来的流程如下：

(1)主叫部分发送INVITE命令，命令中包含有主叫的会话描述(这里称为Remote SDP )。

(2)被叫部分此时处于OpRing的状态中接收到主叫的INVITE消息以后，根据主叫的 INVITE消息和主叫的SDP,得到主叫的地址和主叫的RSVP端口(主叫的RTP端口)；被叫 发送包含有数据流标识和数据业务流特征的PATH消息到主叫。

(3)在完成了一系列SIP命令和状态的交换(RING, OK过程)以后，主叫方开始准备 发送ACK消息了，主叫在下一个过程(收到ACK消息后，打开RTP通道之前)的时候，已 经保证了所有的主叫到被叫之间的路由器都已经收到了 PATH预留消息。

(4)5和6两个消息是主叫端点向被叫端点发送PATH消息，并且接收对端的RESV消息 的过程。

SIP COMET

只有当所有条件满足时，才会发送COMET。

1.SDP扩展

扩展SDP的BNF描述如下：

qos-attribute="a=qos:" strength-tag SP direction-tag[SP confirmation-tag]；服务质量属性 strength-tag= ("mandatory" I "optional" I "success" l"failure")

direction-tag= ("send" I "recv" I "sendrecv") confirmation-tag = "confirm" security-attribute="a=secure:"SP strength-tag SP direction-tag[SP confirmation-tag]
2. SDP实例

以下为从A到B的SIP INVITE中的SDP描述。 

v=0

o=mhandley 2890844526 2890842807 IN IP4  126.16.64.4

s=SDP Seminar

i=A Seminar on the session description protocol

u=http://www.cs.ucl.ac.uk/staff/M.Handley/sd p.03.ps

e=mjh@isi.edu (Mark Handley)

c=INIP4 224.2.17.12/127

t=2873397496 2873404696

m=audio 49170 RTP/AVP 0；媒体类型 a=qos:mandatory recv confirm

"m=video 51372 RTP/AVP 31；媒体类型 a=secure:mandatory sendrecv m=application 32416 udp wb a=orient:portrait

a=qos:optional sendrecv a=secure:optional sendrecv

1.SIP流程

SIP的工作流程如图3.10所示。

策略服务

1.模型

策略服务模型如图3-11所示，其中，issll 为 Intergrated Services over Specific Lower Layers , APS为应用策略服务器。 

2.OSP (Open Settlements Protocol)OSP流程如图3?12所示。 

1)SIP消息

消息如下：

INVITE sip:+1-972-555-5555 @sip.domain2.com;user=phone SIP/2.0

Via: SIP/2.0/UDP phone 1.domain 1.com:5060

From: Henry Sinnreich henry.sinnreich@phone 1 .domain].com； 发端

To: <sip:+1972-555-5555@sip.domain2.com;user=phone>；收端

Callid: 123456 @ domain 1 .com

Cseq: 1 INVITE

Contact: phone 1 .domain 1 .com

SDP

QoS required

2)COPS消息

消息如下：.

REQ OSP =

(Common Header, Client Handle, Context, ClientSI: OSP)

Client Handle = "123456@domainl.com"

Context = "Incoming & Outgoing", "OSP"

ClientSI: OSP = (Called Number, Calling Number)

Called Number = "To: <sip:+1972-555-5555@sip.domain2.com;user=phone>"；收端

Calling Number = "From: Henry Sinnreich；发端

henry.sinnreich @phone 1 .domain l.comn

3)OSP消息

消息如下：

<AuthReq>

<?xml version=1.0?>

<Message messageld=" 123454321" random=n12345678">

<AuthorizationRequest componentId="9876567890M>

<Timestamp>

1999-10-24T17:03:00Z

</Timestamp>

<CallId encoding="base64"> YT64VQpfyF467GhIGfHfYT6jH77n8HHGghyHhHUujhJh756t

</CallId>

<SourceInfo type=Hhenry.sinnreich @phone 1 .domain 1 ,com">

</SourceInfb>

<DestinationInfo type="el64">

1-972-555-5555

</DestinationInfb>

<Service/>

<MaximumDestinations>

5

</MaximumDestinations>

</AuthorizationRequest>

</Message> <AuthReq/>

4)OSP消息

消息如下：

<AuthRsp>

<?xml version=1.0?>

<Message messageld=" 123454321" random="l 2345678 ">

<AuthorizationResponse componentId=H9876567890"> <Timestamp>

1999-10-24T17:03:01Z

</Timestamp>

<Status>、

<Code>

200

</Code>

<Description>

success

</Description>

</Status>

<TransactionId>

67890987

</TransactionId>

<Destination>

<DestinationSignalAddress>

[172.16.1.2]:112

</DestinationSignalAddress>

<Token encoding="base64">

YT64VqpfyF467GhIGfHfYT6jH77n8HHGghyHhHUujhJh756t

HGTrfvbnjn8HHGTrfvhJhjH776tbB9HG4VQbnj7567GhIGfH

6ghyHhHUujpfyF47GhIGfHfYT64VQbnj

</Token>

<ValidAfter>

1999-04-24T17:01:01Z

</ValidAfter>

<ValidUntil>

1998-04-24T17:ll:01Z

</ValidUntil>

<CallId encoding="base64">

YT64VqpfyF467GhIGfHfYT6jH 力 n8HHGghyHhHUujhJh756t </CalUd>

<UsageDetail>

<Service/>

<Amount>

24

</Amount>

<Increment>

3600

</Increment>

<Unit>

s

</Unit>

</UsageDetail>

</Destination>

</AuthorizationResponse>

</Message>

<AuthRsp>

5)COPS消息

消息如下：

DEC = (Common Header, Client Handle, Context,

Decision Flag,Decision: ClientSI Data: OSP)

Client Handle = "123456@domainl.com"

Context = "Incoming & Outgoing"

Decision Flag = "Install"

Decision: ClientSI Data: OSP = (Called Number, Authorization Token)

Called Number = "To: <sip:+1972-555-5555@sip.domain2.com;user=phone>" Authorization Token = "<Token encoding=nbase64n>

YT64VQpfyF467GhIGfHfYT6jH77n8HHGghyHhHUujhJh756t HGTrfvbnjn8HHGTrfvhJhjH776tbB9HG4VQbnj7567GhIGfH 6ghyHhHUujpfyF47GhIGfHfYT64VQbnj

</Token>"

Opt. SIP

SIP/2.0 100 Trying

Via: SIP/2.0/UDP phone 1 .domain 1 .com:5060

From: Henry Sinnreich <henry.sinnreich@phone 1 .domain 1 .com>

To: <sip:+l972-555-5555@sip.domain2.com;user=phone>

Callid: 123456 @ domain 1 .com

Cseq: 1 INVITE

6)SIP消息

消息如下：

INVITE sip:+l-972-555-5555 @sip.domain2.com;user=phone SIP/2.0

Via: SIP/2.0/UDP sip.domain 1 .com:5060

Via: SIP/2.0/UDP phone 1 .domainl .com:5060

From: Henry Sinnreich <henry.sinnreich@phone 1 .domain 1 .com>

To: <sip:+1972-555-5555@sip.domain2.com;user=phone>

Callid: 123456@ domain 1 .com

Cseq: 1 INVITE

Contact: phonel.domainl.com

Record-Route: sip.domainl.com

SDP

QOS required

7)SIP消息

消息如下：

INVITE sip:+l-972-555-5555@sip.domain2.com;user=phone SIP/2.0

Via: SIP/2.0/UDP sip.domain2.com:5060

Via: SIP/2.0/UDP sip.domain 1 .com:5060

Via: SIP/2.0/UDP phone 1 .domain 1 .com:5060

From: Henry Sinnreich <henry.sinnreich @ phone 1 .domain 1 .com>

To: <sip:+l972-555-5555@sip.domain2.com;user=phone>

Callid: 123456@domain 1 .com

Cseq: 1 INVITE

Contact: phone 1 .domain 1 .com

Record-Route: sip.domainl.com

SDP

QOS required '

8)SIP消息

消息如下："

SIP/2.0 183 Session Progress

Wa: SIP/2.0/UDP sip.domain2.com:5060

Via: SIP/2.0/UDP sip.domainl.com:5060

Via: SIP/2.0/UDP phone 1 .domain 1 .com:5060

From: Henry Sinnreich <henry.sinnreich @phone 1 .domain 1 .com>

To: <sip:+1972-555-5555@sip.domain2.com;user=phone>;tag=134159

Callid: 123456@domain 1 .com 

Cseq: 1 INVITE

SDP

QoS required

9)COPS消息

消息如下：

REQ AssuredLDP=

(Common Header, Client Handle, Context, ClientSI: ConfigLocalPolicy)

Client Handle = " 123456 @ domain 1 .com"

Context = "Configuration Request" ,nConfigLocalDecisionPolicy"

ClientSI: ConfigLocalDecisionPolicy = ( Caller Media Address, Caller Media

Port, Caller SDP info, Callee Media Address, Callee Media Port, Callee SDP

info)

10)COPS 消息

消息如下：

DEC =

(Common Header, Client Handle) (Decision) I (Error)

Client Handle = nR1001"

Decision = (Context, Decision Flag, Named Decision Data: Config Local DecisionPolicy)

Context = "Configuration Request", "ConfigLocalDecisionPolicy"

Decision Flag = "Install"

Named Decision Data: (Binding Count, PRID, BPD)

Binding Count = 1

PRID = "1.2.3.4"