Samsung Ubigate iBG1000, Руководство пользователя

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CHAPTER 3. Software Overview
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© SAMSUNG Electronics Co., Ltd.
(Continued)
WAN Protocols Descriptions
HDLC High-Level Data Link Control (HDLC) is a bit-oriented
synchronous data link layer protocol developed by the
International Organization for Standardization (ISO).
The original ISO standards for HDLC were:
- ISO 3309 - Frame Structure
- ISO 4335 - Elements of Procedure
- ISO 6159 - Unbalanced Classes of Procedure
- ISO 6256 - Balanced Classes of Procedure
The current standard for HDLC is ISO 13239, which replaces all
of those standards. HDLC provides both connection oriented
and connectionless service. HDLC can be used for point to
multipoint connections, but is now used almost exclusively to
connect one device to another, using what is known as
Asynchronous Balanced Mode (ABM). The other modes are
Normal Response Mode and Asynchronous Response Mode.
PPP The Point-to-Point Protocol (PPP) provides a standard method
for transporting multi-protocol datagram over point-to-point links.
These links provide full-duplex simultaneous bi-directional
operation and are assumed to deliver packets in order.
PPP is comprised of 3 main components:
A method for encapsulating multi-protocol datagram. In Ubigate
iBG1000, PPP is used on the links that use HDLC-like framing
(on the WAN side over T1 physical interfaces). The details of the
encapsulations can be found in RFC1662 and RFC2516.
A Link Control Protocol (LCP) for establishing, configuring and
testing the data-link connection. The details of this can be found
in RFC 1661.
A family of Network Control Protocols (NCPs) for establishing
and configuring different network layer protocols. There is a NCP
for each network protocol for example, IPCP for IP networks.
Optionally, before PPP NCP is established, peers may need to
authenticate themselves and any failure during this can result in
the link termination.
There are two authentication protocols: Password Authentication
Protocol (PAP) and Challenge Handshake Authentication
Protocol (CHAP). In addition to the above, PPP will also
interface with AAA for username/password validations.
The PPP is the most ubiquitous WAN protocol today for internet
access and/or leased line connectivity to a remote office.
When the bandwidth requirements go beyond a single T1 (and
DS3 being expensive or unavailable) multilink PPP can be used
to create a bigger bandwidth pipe.