Article ID: 148499 - View products that this article applies to.
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This article contains information describing technical aspects and the usage of the SLIP and PPP line-control protocols with Dial-Up Networking.
Microsoft's Windows 95 implementation of the SLIP and PPP protocols is based on the standards set forth by the Internet Engineering Task Force (IETF). These standards are contained in technical documents called Requests For Comments (RFC) and are widely available on the Internet. By adhering closely to these standards, connectivity to other SLIP or PPP servers similarly designed is virtually guaranteed.
Brief outlines of the protocols themselves are provided below, with information pertinent to their operation with Windows 95 following.
If more information on either protocol is required, the following RFCs are good sources of information:
RFC-1055: SLIP Implementation RFC-1661: PPP Implementation RFC-1700: Internet Assigned Numbers
Serial Line Internet Protocol - SLIPSLIP can be defined as an encapsulation method for transmitting IP packets over a serial connection. From its creation until the present time, the recommended method for implementing SLIP has remained a de facto standard.
Special Characters END (C0h,192d) Signals the end of a packet's transmission. ESC (DBh,219d) Special character used when characters duplicate the END character. NOTE: If a data byte has the same value as the END character, a two-byte sequence of ESC and DCh is sent instead. If a data byte is the same as an ESC character, a two-byte sequence of ESC and DDh is sent instead.
IP (headers and data) + transport protocol headers - framing characters <= 1006 bytes
Other InformationSLIP does not have the ability to transmit more than one network protocol at a time. Its architecture does not provide a method of differentiating between network protocols. TCP/IP is the protocol that is typically used with SLIP, which made it ideal for connecting a remote computer to the Internet using a dial-up SLIP server. However, because TCP/IP is the only network protocol SLIP can carry makes it of limited use in other applications.
SLIP also provides no mechanisms for error correction. It relies on the hardware used to make the connection, and the error-correction capabilities of TCP/IP to determine if a packet's information is bad and needs to be resent.
There are no compression algorithms built into SLIP. There are variants of SLIP (for example, CSLIP, or Compressed SLIP) that provide some degree of streamlining, but the majority of SLIP connections do not use compression.
Point to Point Protocol - PPPPPP can be defined as an encapsulation method for transmitting multiple- protocol datagrams over point-to-point links. It is more robust and versatile than its predecessor, SLIP. PPP provides a data-link layer, the Link Control Protocol (LCP), for setting up, configuring, and monitoring the connection to ensure that the connection remains reliable. In addition, by using Network Control Protocols (NCPs), different network- layer protocols can be used dynamically.
Protocol Field (xxxxxxxx,yyyyyyyy) The Protocol field is one or two octets, and its value identifies the datagram encapsulated in the Information field of the packet. The field is transmitted and received most- significant-octet first. Information Field (0 - n[xxxxxxxx]) The Information field is zero or more octets. The Information field contains the datagram for the protocol specified in the Protocol field. The maximum length for the Information field, including padding, but not including the Protocol field, is termed the Maximum Receive Unit (MRU), which defaults to 1500 octets. By negotiation, consenting PPP implementations may use other values for the MRU. Padding (0 - n[xxxxxxxx]) On transmission, the Information field may be padded with an arbitrary number of octets up to the MRU. It is the responsibility of each protocol to distinguish padding octets from real information.
Phase I Each side exchanges LCP packets that test the integrity of the link and configure the operational parameters the connection will use at the data-link layer. Phase II Each side negotiates for and participates in user authentication. This phase is only a suggestion to the standard implementation of a point-to-point protocol, and as such, may not be included in all implementations. Phase III Each side negotiates for the set of NCPs that will be used. For each different type of datagram to be exchanged (IPX, IP, and so on), an NCP must be configured and operational. This provides the method for transmission of network-layer information.
Other InformationThe most important thing to remember about PPP is that it can support multiple network protocols simultaneously, or any individual protocol by itself. In addition, it provides error correction and compression of a very sophisticated nature. While it has more overhead and additional information, the compression and error control make PPP much faster than SLIP and far more reliable.
Using SLIP and PPP with Windows 95Windows 95 automatically supports dialing into servers that allow PPP, RAS, or NRN (NetWare Connect) connections. SLIP support must be installed separately. If you are using the CD-ROM version of Windows 95, you can install SLIP support (along with scripting support) by following these steps:
NOTE: If you do not have the CD-ROM version of Windows 95, see the following articles in the Microsoft Knowledge Base for information about obtaining SLIP support:
135315When you are using SLIP, you are limited to the use of the TCP/IP protocol. In addition, in the Dial-Up Networking connectoid, the Enable Software Compression and Require Encrypted Password options will not be available. These restrictions are limitations of the SLIP protocol, as noted previously.
(http://support.microsoft.com/kb/135315/EN-US/ )CD-ROM Extras for Microsoft Windows 95 Upgrade
(http://support.microsoft.com/kb/146238/EN-US/ )Microsoft Windows 95 Service Pack 1 Admin.doc File (3 of 3)
When you are using PPP, you can use the full flexibility of Dial-Up Networking. You can select NetBEUI, IPX/SPX, TCP/IP, or any combination thereof. The compression and password-encryption options are also available. However, if the dial-up server does not support either of these options, they will not be used. The use of these options is negotiated during the second phase of the PPP connection.
With the addition of Microsoft Plus! for Windows 95, a computer running Windows 95 can be used as a dial-up server. However, incoming SLIP connections are not supported, as Windows 95 is not designed to route TCP/IP packets. Incoming PPP connections using NetBEUI or IPX/SPX are supported, and offer the remote computer access to the host's resources. If the host computer is connected to a LAN, the remote computer can gain access to network resources, and even be validated by a Microsoft Windows NT or Novell NetWare server.
For information about how to obtain RFC documents, please see the following article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/185262/EN-US/ )How to Obtain Request for Comments Documents from the Internet
Article ID: 148499 - Last Review: August 7, 2012 - Revision: 2.0