Microsoft KB Archive/235610

= Overview of Multilink and Bandwidth Allocation Protocol (BAP) =

Article ID: 235610

Article Last Modified on 2/27/2007

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APPLIES TO


 * Microsoft Windows 2000 Server
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Professional Edition

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This article was previously published under Q235610



SUMMARY
Windows 2000 remote access supports multilink connections and Bandwidth Allocation Protocol (BAP). With a multilink connection, multiple physical links appear as a single logical link over which data is sent and received.



MORE INFORMATION
A multilink connection is appropriate when you are combining multiple B channels of a Basic Rate Interface (BRI) connection because the support for bonding (the combining of Integrated Services Digital Network [ISDN] B channels through hardware support) is specific to the ISDN adapter. You can use a multilink connection for any ISDN adapter, but the multilink connection must be supported on both sides of the connection.

Although you can aggregate multiple physical links with a multilink connection, there is no mechanism to adapt to changing bandwidth conditions (for example, adding or terminating extra links when necessary). This additional capability is provided with BAP, which uses a multilink connection to dynamically manage links.

For example, a BAP-enabled remote access client and remote access server create a multilink connection that consists of a single physical link. As the usage of the single link rises to a configured level, the remote access client uses a BAP request message to request an additional link. The BAP request message specifies the type of link needed (for example, an analog phone line or an ISDN or X.25 connection). The remote access server sends a BAP response message that contains the phone number of an available port on the remote access server of the same type as specified by the remote access client in the BAP request.

The specific protocols that make up these dynamic BAP features include:
 * Bandwidth Allocation Protocol (BAP)
 * Bandwidth Allocation Control Protocol (BACP)
 * Extensions to Link Control Protocol (LCP)

BAP
You can use BAP for link management. BAP defines packets, parameters, and negotiation procedures to allow two endpoints to negotiate gracefully, adding and dropping links from a multilink bundle as noted in Request for Comments (RFC) 2125.

BACP
BACP works in conjunction with BAP as an associated control protocol. BACP uses the same packet exchange mechanism as LCP.

LCP Extensions
A new LCP configuration option is used to declare a unique discriminator for the link that is used to send the option.

Please refer to RFC 2125 for specification details about BAP, BACP, and LCP. Microsoft implements BAP as part of RAS Access Policies (RAP) in Windows 2000. It can be managed using either Routing and Remote Access Services (RRAS) or Internet Authentication Service (IAS).

For additional information, click the article numbers below to view the articles in the Microsoft Knowledge Base:

233171 How to Configure Client-Side Bandwidth Allocation Protocol

233151 How to Configure Server-Side Bandwidth Allocation Protocol

Additional query words: multi

Keywords: kbenv kbinfo kbnetwork KB235610

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