Volume 1 - Chapter 3: Fundamentals of WANs and IP Routing

Question 1

What are the two types of data-link protocols used for leased lines?

Answer 1

Point-to-Point (PPP) and High-Level Data Link Control (HDLC)

Question 2

Describe the characteristics of a leased line service.

Answer 2

1) A physical layer service
2) Operates at a predetermined speed
3) Uses full-duplex logic

Question 3

A leased line conceptually acts as if you had a ____________ link between two routers.

Answer 3

Full duplex ethernet link

Question 4

A T1 is an example of a?

Answer 4

Leased line

Question 5

T1 lines operate at what speed?

Answer 5

1.544 Mbps

Question 6

A line whose data cannot be copied by other telco customers is referred to as a ______

Answer 6

Private line

Question 7

What layer do leased lines function at?

Answer 7

Layer 1

Question 8

The flag field in a HDLC frame is equivalent to what field in an Ethernet frame?

Answer 8

The preamble; used to synchronize devices so they realize a new frame is arriving

Question 9

The destination address field in a HDLC frame is equivalent to what field in an Ethernet frame?

Answer 9

This field is also refered to as a destination address on an Ethernet frame as well.

Question 10

The Type field in a HDLC frame is equivalent to what field in an Ethernet frame?

Answer 10

This field is also refered to as the type on an Ethernet frame as well.

Question 11

The FCS field in a HDLC frame is equivalent to what field in an Ethernet frame?

Answer 11

This field is also refered to as the FCS on an Ethernet frame as well.

Question 12

Describe what happens to an Ethernet frame when it passes across a HDLC WAN.

Answer 12

The packet is removed from its Ethernet frame and is encapsulated into an HDLC frame, then passed across the WAN. Then the packet is removed from the HDLC frame and re-encapsulated into an Ethernet frame.

Question 13

Which traditional leased line technology is newer and supports additional features?

Answer 13

PPP

Question 14

A WAN link that utilizes Ethernet to build a topology between only two routers is referred to as a ______.

Answer 14

Ethernet Point-to-Point link

Question 15

A E-Line service is an example of a?

Answer 15

Ethernet Point-to-Point link

Question 16

Describe what happens to an Ethernet frame when it passes across an Ethernet WAN.

Answer 16

The packet is removed from its Ethernet frame and is encapsulated into a different Ethernet frame, then passed across the WAN. Then the packet is removed from the Ethernet frame and re-encapsulated into a new Ethernet frame as it is passed onto the WAN.

Question 17

The term “path selection” is often used to describe the ________.

Answer 17

Routing process

Question 18

Describe the 4 step process in routing when a router receives a frame destined for another subnet.

Answer 18

Step 1) Check FCS and discard corrupt frames

Step 2) Discard the old Ethernet header and trailer

Step 3) Make a forwarding decision based on the available routes for the destination

Step 4) Encapsulate the IP packet in a new Ethernet header and trailer, then forward the frame

Question 19

How many bytes are in an IPv4 header?

Answer 19

20 bytes