Bandwidth Allocation Protocol (BAP)

Bandwidth Allocation Protocol (BAP) generally manages the total number of links in a multilink bundle. It is especially valuable to different operations that usually contain carrier charges based on bandwidth utilization. It is basically a Point-to-Point Protocol (PPP) that is required to dynamically add or remove additional connections or links to a multi-point bundle or connection. It defines and explains datagrams simply to coordinate adding or removing additional inks in a multilink bundle. It also helps in specifying which of the peer is usually responsible for decisions regarding managing and controlling bandwidth during a multilink connection.

It also defines packets, parameters, and negotiation procedures simply to allow two of the endpoints to negotiate gracefully adding and dropping links. It is most importantly required over Integrated Services Digital Network (ISDN) connections due to the reason that these dial-up services might instantly add or drop lines. Dynamic BAP is required to facilitate dynamic allocation of links for multilink connection. Dynamic BAP consists of various protocols as given below :

1. Bandwidth Allocation Protocol (BAP)
2. Bandwidth Allocation Control Protocol (BACP)
3. Link Control Protocol (LCP) 

BAP Functions :

1. It dynamically controls how bandwidth can be allocated.
2. It also provides an efficient and effective mechanism for simply managing and controlling costs while dynamically providing optimum bandwidth.
3. It is required to modify connections or links among a data link protocol with taking on designated responsibilities for decision making as it basically relates to bandwidth management.
4. It allows the administrator to configure the PPP server to simply specify and identify which of the particular multilink lines can be added or dropped.
5. It also adds features to PPP and multilink to monitor and manage all connection requirements and to adjust accordingly.

BAP Header format :
BAP Header generally consists of 5 fields as given below :

1. Type field –
   This field is of 8 bits. It generally specifies the type of BAP message or datagram packet being sent or transmitted. Types of messages or datagrams are given below in the table :

   Type	Description
   01	Call-Request
   02	Call-Response
   03	Callback-Request
   04	Callback-Response
   05	Link-Drop-Query-Request
   06	Link-Drop-Query-Response
   07	Call-Status-Indication
   08	Call-Status-Response

2. Identifiers field –
   This field is of 8 bits.
3. Length field –
   This field is 16 bits. It generally helps to represent the total length of the packet or message.
4. Data field –
   This field varies in length.
5. Response code field –
   This field is of 8 bits. It is also binary coded. It contains the following values :

   Code	Description
   00000000	Request-Ack
   00000001	Request-Nak
   00000010	Request-Rej
   00000011	Request-Full-Nak