Variability in delay is called ________. A) jitter B) ...

[kaid0807]

Variability in delay is called ________.
 
  A) jitter
  B) variance
  C) a QoS failure
  D) latency

Question 2

List and briefly describe the four elements that a PDU can contain.
 
  What will be an ideal response?

[eliasc0401]

Answer to Question 1

A

Answer to Question 2

1. a destination service access point (DSAP), 2. a source service access point (SSAP), 3 . a control field, and 4. a data or information field. The DSAP is an 8-bit field that identifies the higher-level protocol using the LLC's services. Remember, the frame has been passed down to the data link layer from a higher-level layer in the TCP/IP layer stack. That higher-level layer uses a specific type of protocol. The first bit of the eight-bit DSAP field indicates whether the frame is meant for an individual host or a group of hosts. A host is any device that can communicate with and is connected to a TCP/IP network. The SSAP is also an eight-bit field that indicates the local user of the LLC service. The SSAP's first bit indicates whether the protocol data unit communication is a command or a response type of frame. The control field, the third element of a PDU, is a one- or two-byte field that indicates the type of PDU. PDU frames are one of the following: information (I), supervisory (S), or unnumbered (U). Only Type 2 connection-oriented delivery services use I and S frames. All three delivery types use U frames. Information frames are used to transmit connection-oriented data. Supervisory frames are used to supervise and manage the information frames. Unnumbered frames are used for connectionless data and to terminate the logical link between hosts using Type 2 services. The fourth protocol data unit element, the data field, is of variable length and contains the data or information received from the network layer protocol. The length of the data field will be determined by the media access method used; for example, token or contention. We explore both later when we discuss MAC in more detail. Of the three types of PDU frames, supervisory frames do not have a data field. Figure 5.2 illustrates the components of a PDU.