All about HDLC and Point to point protocol.

1. HDLC & PPP
Presented By: KINZA RAZZAQ

2. HDLC HDLC(High-Level Data Link Control) is a group of
protocols or rules for transmitting data between
network points(nodes).

3. Working In HDLC, the date is organized into a unit(frame) and
sent across a network to a destination that verifies
it’s successful arrival.The HDLC protocol also
manages the flow or pacing(stepping) at which the
data is being sent

4. Features
HDLC is one of the most commonly used protocol and support full duplex
approach. Broadly HDLC features are as follows:
■ Reliable protocol
– selective repeat or go-back-N
■ Full-duplex communication
– receive and transmit at the same time
■ Bit-oriented protocol
– use bits to stuff flags occurring in data.
■ Flow control
– adjust window size based on receiver capability
■ Uses physical layer clocking and synchronization to send and receive
frames

5. Stations
STATIONS
PRIMARY
STATION
SECONDARY
STATION
COMBINED
STATION

6. Balanced & Unbalanced Mode
.
Primary
Secondary Secondary
Commands
Responses
Combined Combined
commands/Responses
Unbalanced Mode
Balanced mode

7. Frames
HDLC
FRAMES
U-frame I-frame S-frame

8. Point-to-point
Protocol
In computer
networking, Point-to-Point
Protocol (PPP) is a data
link (layer 2) protocol used to
establish a direct connection
between two nodes.

9. Connection
■ It connects two routers directly
without any host or any other
networking device in between.
■ It can provide
connection authentication,
transmission encryption.

10. Origin
■ PPP was designed somewhat after the original HDLC(High-Level Data
Link Control) specifications. The designers of PPP included many
additional features that had been seen only in proprietary(branded)
data-link protocols up to that time.
■ PPP was designed to work with numerous network layer protocols,
including Internet Protocol (IP), Novell's Internetwork Packet
Exchange (IPX), etc.
■ PPP is specified in RFC 1661.

11. Usage
■ PPP is used over many types of physical networks including serial
cable, phone line, trunk line, cellular telephone, specialized radio links,
and fiber optic links.
■ PPP is also used over Internet access connections.
■ Internet service providers (ISPs) have used PPP for customer dial-up
access to the Internet, since IP packets cannot be transmitted over
a modem line on their own, without some data link protocol.

12. Usage
■ PPP is commonly used as a data link layer protocol for connection
over synchronous and asynchronous circuits, where it has largely
superseded (outdated) the older Serial Line Internet Protocol (SLIP) and
telephone company mandated standards (such as Link Access Protocol,
Balanced (LAPB). The only requirement for PPP is that the circuit
provided be duplex.
■ Like SLIP, this is a full Internet connection over telephone lines via
modem. It is more reliable than SLIP because it double checks to make
sure that Internet packets arrive intact(complete). It resends any
damaged packets.

13. Derivatives
1
Point-to-Point Protocol over
Ethernet (PPPoE) is a method for
transmitting PPP
over Ethernet that is sometimes
used with DSL.
2
Point-to-Point Protocol over
ATM (PPPoA) is a method for
transmitting PPP
over ATM Adaptation(version) Layer 5
(AAL5), which is also a common
alternative to PPPoE used with DSL.

14. Components
■ PPP is a layered protocol that has three components:
1. An encapsulation component that is used to transmit
datagrams (unit of transfer) over the specified physical layer.
2. A Link Control Protocol (LCP) to establish, configure, and test the link
as well as negotiate capabilities.
3. One or more Network Control Protocols (NCP) used to negotiate
optional configuration parameters and facilities for the network layer.
There is one NCP for each higher-layer protocol supported by PPP.

15. Looped Link Detection
PPP detects looped links using a feature
involving magic numbers. When the node
sends PPP LCP messages, these messages
may include a magic number. If a line is
looped, the node receives an LCP message
with its own magic number, instead of getting
a message with the peer's magic number.

16. Configuration Options
■ Authentication - Peer routers exchange authentication messages. Two authentication
choices are Password Authentication Protocol (PAP) and Challenge Handshake
Authentication Protocol (CHAP).
■ Compression - Increases the effective throughput on PPP connections by reducing the
amount of data in the frame that must travel across the link. The protocol
decompresses the frame at its destination.
■ Error detection - Identifies fault conditions. The Quality and Magic Number options
help ensure a reliable, loop-free data link. The Magic Number field helps in detecting
links that are in a looped-back condition. Until the Magic-Number Configuration
Option has been successfully negotiated, the Magic-Number must be transmitted as
zero. Magic numbers are generated randomly at each end of the connection.

17. Line Activation & Phase