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Answers to the Chapter 3 "Do I Know This Already?" Quiz 709
6
Describe the features required for a protocol to be considered connection-oriented.
The protocol must either exchange messages with another device before data is allowed
to be sent, or some pre-established correlation between the two endpoints must be defined.
TCP is an example of a connection-oriented protocol that exchanges messages before data
may be sent; Frame Relay is a connection-oriented protocol for which pre-established
correlation between endpoints is defined.
7
In a particular error-recovering (reliable) protocol, the sender sends three frames,
labeled 2, 3, and 4. On its next sent frame, the receiver of these frames sets an
acknowledgment field to 4. What does this typically imply?
Setting the acknowledgment field to 4 implies that frames through number 3 were
received successfully. Most windowing, error-recovery (reliable) protocols use forward
acknowledgment.
8
Name three connection-oriented protocols.
TCP, SPX, LLC Type 2, and X.25 are some examples of connection-oriented protocols
that happen to provide error recovery. ATM and Frame Relay are also connection-
oriented, but without error recovery.
9
Name three terms popularly used as synonyms for MAC address.
NIC address, card address, LAN address, hardware address, Ethernet address, Token Ring
address, FDDI address, and burned-in address are used synonymously with MAC address.
All of these names are used casually and in formal documents, and they refer to the same
6-byte MAC address concept as defined by IEEE.
10
What portion of a MAC address encodes an identifier representing the manufacturer of the
card?
The first 3 bytes. For instance, Cisco is assigned 0000.0C as one of its Organizationally
Unique Identifiers (OUIs). Many Cisco router Ethernet interfaces have MAC addresses
beginning with that value. The output of the show interface command for a LAN interface
lists the burned in address after the acronym BIA.
11
Are DLCI addresses defined by a Layer 2 or a Layer 3 protocol?
Layer 2. While not specifically covered in this chapter, Frame Relay protocols do not
define a logical addressing structure that can usefully exist outside a Frame Relay
network; by definition, the addresses would be OSI Layer 2 equivalent.
12
How many bits are present in a MAC address?
MAC addresses comprise 48 bits. The first 24 bits for burned-in addresses represent a code
that identifies the manufacturer.
apA.fm Page 709 Monday, March 20, 2000 5:24 PM