The both machines must use the same dial -up protocol, to ensure the safe reliable transmission of data over phone lines between a dial-up server and a remote computer.  The protocol you use depend on the dial-up server, like if you connected to Internet Service Provider, you would use Point to Point Protocol. Dial-Up Networking supports :-

• Point to Point Protocol
• NetWare connect
• Remote Access Service
• Serial Line Interface Protocol

Point to Point Protocol

     Point to Point Protocol (PPP) is the standard for all types of remote access connection, as all Internet Service Providers offer PPP access to Internet. The secret in its features like link-quality testing, header compression, and error checking, it also supports network protocols: NetBEUI, IPX/SPX, and TCP/IP.

NetWare Connect Protocol

     The NetWare connect protocol is used by NetWare servers. This protocol adds the following features to the NetWare server:

• A proprietary Remote Access Service dial up protocol
• Modem sharing and pooling
• Remote workstation control

     NetWare Connect dial-up servers don't support software compression and with only the IPX/SPX network protocol.

Remote Access Service Protocol

      The Remote Access Service (RAS) Protocol is a variant of NetBEUI called asynchronous NetBEUI that is designed to over slower serial links. To use RAS, both the client and the server must be running the NetBEUI network protocol. RAS doesn't support multiple network protocol the way PPP does.

Serial Line Interface Protocol

      The Serial Line Interface Protocol (SLIP) is a simple protocol designed to work with TCP/IP network protocol. Until PPP came along, SLIP was the standard Internet dial-up protocol for many years. Now  SLIP is not  widely used because of the following reasons:-

1. SLIP doesn't implement error correction: SLIP doesn't perform error correction unlike PPP, as a result that may led to send extra packet data to make the error checking.
2. SLIP can handle only one protocol at a time: The SLIP header doesn't include a field for specifying the network protocol, unlike IP header which can handle more than one protocol, so you can't change while working, you must end your session first.
3. SLIP can't handle dynamic addressing: SLIP requires that the machine must determine an IP address. This prevents you from using Dynamic Host Configuration Protocol (DHCP)
4. SLIP doesn't support compression: The basic SLIP protocol doesn't support compression of the entire data packets. However, a different SLIP specification called compressed SLIP or CSLIP which enables compression of just the IP header portion of a TCP/IP data packet.