Services are performed by protocols in layer n server


Services are performed by protocol(s) in layer N (server
layer) for layer N+1 (client layer) across an interface.

Protocols are used to implement services .

Protocols can change without affecting service.

A set of layers that defines a network is called a
protocol stack (aka “architectures”, “suite”, or
“models”)
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TDC-463
Protocols

Clients and servers must follow a set of rules
called a protocol which determines

Packet format

Permissible requests and responses

Format of header information and data

Packet ordering and timing

Protocol standards are documents that define
protocols.

Internet protocol standards are called Request for
Comments (RFCs).

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OSI Stack
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Must know layer names and general services

TDC-463
Layer 1 – Physical layer

Physical layer coordinates functions to transport
traffic over physical medium

Physical layer protocol specifies the following
services to the data link client

Physical characteristics of interfaces and media

Supported transmission line rate (or channel bandwidth)

Bit encoding method (e.g. NRZ, NR, QAM, PSK, etc)

Block encoding methods (e.g. 8b10b)

Bit, timeslot, frame synchronization

Multiplexing (e.g. TDM, FDM, WDM)

Line protection

Operations, Administration, and Maintenance (OAM) for
the physical layer
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Layer 2 - Data Link Layer
Key Services

A Data Link layer protocol may support some or all of the
following services to the network layer client
1. Framing
2. Client layer encapsulation
3. Physical addressing
4. Flow control
5. Error detection
6. Error control
7. Link management
8. Congestion notification
9. Switching (virtual circuit or datagram)
10.Media access control (for broadcast networks)
11.Traffic management (CoS, QoS, Policing, Shaping)
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Layer 3 - Network Layer

The network layer is responsible for the delivery
of individual packets from the source host to the
destination host.

Network layer is responsible for the following
services:

Logical addressing

Packet routing from source to destination

Examples of network layer protocols?

IP (Internet Protocol), Appletalk, IS-IS
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Network Layer
Source-to-destination delivery
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Network and Underlying Layers
Client-Server Abstraction

Client Server layer abstraction example
41
Network
layer
Data Link
layer
Physical
layer
Router R1
Router R2 Router R3
Ethernet SW1
Ethernet SW2
Ethernet SW3
Ethernet SW4
SONET/WD
network
SONET/WD
M Transport
network
Ethernet 100Base-FX

TDC-463
Layer 4 – Transport Layer

The transport layer is responsible for the delivery
of a message from one process to another
process

Transport layer is responsible for the following
services:

Service Point (aka process) addressing

Service “Multiplexing”

Connection control between source and destination

Flow control between source and destination

Error control between source and destination

Segmentation and reassembly

Network congestion control

Examples of transport layer protocols

Transmission Control Protocol (TCP), UDP
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