Troubleshooting The Layers - ASCOM Myco 3 Troubleshooting Manual

TROUBLESHOOTING GUIDE
Ascom Myco 3
Internet layer -
Link layer MAC sublayer
Physical sublayer
Application Level
The application layer includes the functions of OSI Application, Presentation Layer and Session Layer,
which are often referred to as a user services. TCP/UDP sockets and ports are used to describe the path
over which applications communicate. Most application level protocols are associated with one or more
port number.
The SIP protocol is an Application Layer protocol designed to be independent of the underlying Transport
Layer.
Transport Layer
TCP packets are routed using the IP addresses of WLAN network devices that may interwork with other
networks such as the internet or Public Switched Telephone Network (PSTN). In the context of the VoWiFi
system this is likely to be a VoIP gateway or IP-PBX.
The transport layer also provides congestion throttling to maximize data throughput without overwhelming
the resources of the network.
Internet Level
The Internet level provides the IP address used by network devices, and responds to UDP and TCP service
requests from the transport layer and provides network to network routing.
Link Layer - MAC and Physical Sublayers
The physical sublayer and MAC sublayer, in the context of the TCP/IP model, replaces the data link and
physical layers of the OSI model with a single link layer. This means that the link layer:
• Controls how data, in the form of bit streams, is transmitted through the network on standard RF
channels. The layer is the interfaces between the RF channel and the network devices such as the APs,
and handsets. The notion of the physical layer also defines the protocols that define the characteristics
of the channels conveying data. The handset uses the standard RF channel on either the 2.4 GHz band
or the 5GHz band.
• Manages the raw bit stream data received by the AP from the handset radio, and packages the bits into
802.11 frames. 802.11 defines three kinds of frame for WLANS, one for management, one for control and
one for data. The handset uses management and control frames for AP association and authentication.
• The MAC sublayer manages the physical MAC addressing scheme by encapsulating layer 2 PDUs in a
MAC sublayer PDU. The MAC sublayer uses Address Resolution Protocol to maintain logical IP to
physical MAC address mapping of SIP servers in the call path.
4.1.1

Troubleshooting the Layers

Understanding the layers in the TCP/IP protocol stack and how they communicate with each other is
important because it provides the support engineer with a consistent, structured and methodological
TD 93297EN / 19 December 2019 / Ver. B
IP packets
802.11 frames
(Management, control and
data frames)
RF signals, digitized bit
streams
The Handset as a WLAN Wireless Client
IP addressing - APs, controllers.
The handset uses the IEEE 802.11
WLAN standard protocol suit to get
access to the media and to send
packets to the AP.
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