Switched Digital Video

Question 1

CRAN

Answer 1

Converged Regional Area Network

Question 2

The ____ takes the reconditioned video streams to move
from the Master Headend to each local Headend,
hubsite and OTN on the Comcast Network.

Answer 2

converged regional area network. CRAN

Question 3

256 QAM

Answer 3

8 bits per symbol * the symbol rate
(5.361 million symbols) = 42.88 Mbps of raw
data.

Question 4

What are the limitations of SDV( switched digital video)

Answer 4

Must
be received as CBR, Expensive to
implement with new hardware, Limited
Bandwidth.

Question 5

What are the benefits of SDV(switched digital video)

Answer 5

Saves
Bandwidth for more products and services,
will be able to compete with other rival
companies.

Question 6

How many channels are currently

available on the 750 MHz lineup?

Answer 6

116

Question 7

What component receives the national

content?

Answer 7

CMC, comcast media center.

Question 8

How many Mbps does each service
group receive when 4 QAMs are
utilized?

Answer 8

Approximately 136

Question 9

How can our customers benefit from

SDV(switched digital video)?

Answer 9

They will be able to enjoy more
services from our network and access
other products with more flexibility due to
the saved bandwidth.

Question 10

used for video compression/decompression processess

Answer 10

a video codec.

Question 11

How Does MPEG Work?

Answer 11

The MPEG the picture is broken up into
rectangular areas called macroblocks, each of
which has its own motion vector.

Question 12

list picture hierarchy

Answer 12

• Frame
• Slice
• Macroblock
• Block

Question 13

MPEG includes what encoded pictures?

Answer 13

• I - Frames
• B - Frames
• P - Frames

Question 14

What is CBR (constant Bit Rate)?

Answer 14

CBR or Constant bit rate encoding means that
the rate at which the codec’s output should be
constant. As we stated in the last module, it
ensures a steady data flow.

Question 15

What is VBR(variable bit rate)?

Answer 15

VBR or Variable bit rate encoding means that
the rate at which the codec’s output will vary its
output data per time slot.
This allows for a higher bit rate for more
complex segments while less space will be
allocated for the stream.

Question 16

How many MPEG packets can fit inside

one Ethernet packet?

Answer 16

7

Question 17

how many packets are in an Ethernet packet?

Answer 17

1500

Question 18

Why is it critical that Comcast utilizes

CBR when implementing SDV?

Answer 18

The
video feed must be constant so there isn’t
a heavy load of traffic at any point, which
would consume too much bandwidth,
possibly making services unavailable for
certain customers.

Question 19

Describe the importance of MPEG in

the Comcast Network under SDV.

Answer 19

MPEG is what makes SDV possible. Its
compression allows the video to be sent to
customers while maximizing the
throughput of the switched digital stream.

Question 20

In a GOP, which frame type acts as

the headers?

Answer 20

I Frame

Question 21

In a GOP, which frame type can be

encoded without prediction?

Answer 21

B Frames

Question 22

In a GOP, which frame type can be

coded with forward prediction?

Answer 22

P frames

Question 23

Used to borrow bits from the

network number to identify hosts

Answer 23

Subnet mask

Question 24

Identifies endpoints

sharing the same network.

Answer 24

Network number

Question 25

Identifies a specific endpoint

Computer or Computer Network

Answer 25

Host number

Question 26

Public IP

Answer 26

Routable on the Internet. This
type of IP address can be assigned to a
router and manage several servers
including Web, FTP, DNS, etc.

Question 27

Private IP

Answer 27

Not routable on the Internet.
This type of IP address is commonly
granted by a DHCP Server and resides
behind a firewall, protected from
intruders on the Internet. A Private IP
address allows a single location to take 1
Public IP address (or many) and create a
secure network of hundreds or more
devices. This process, known as
subnetting will be discussed later.

Question 28

name the 3 types for IPv6 addresses

Answer 28

Unicast, Multicast, anycast

Question 29

what is SNMP( Simple network management protocol)?

Answer 29

SNMP is an application protocol used to
communicate management information between
the network management stations and the
“agents” in the network elements through
virtual connections.
SNMP manages network resources through a
database called a Management Information
Base (MIB). MIBs are composed of managed
objects in a strict format, which define the
statistical values and parameters of an
element’s operation. Each managed object has
an Object Identifier (OID) to distinguish it
from other objects.

Question 30

What IP version is currently in use

today?

Answer 30

IPv6

Question 31

What is the purpose of subnetting?

Answer 31

It
allows a large network to be broken down
into several smaller networks. Helps for
organization of IP address blocks, and
smaller companies can effectively use
addresses.

Question 32

re-encoder

Answer 32

takes content from several
places, such as the IP Backbone and CRAN, and
improves the video quality before sending it
over to the Bulk Encryptor.
The Re-encoder performs these tasks at a
National, Regional and Local Video levels.
The video feeds are received as MPTS and leave
the headends via SPTS CBR.

Question 33

What would occur if the SDVSM(switched digital video session manager) was
inactive?

Answer 33

No SDV sessions could be
requested – Switched Digital channels would
not be able to be viewed

Question 34

What is the primary function of the

ERM(edge resource manager)?

Answer 34

Managing bandwidth and program
resources on Edge QAMs for join/leave
multicasts.

Question 35

What is stored in the mini-carousel?

Answer 35

Channel Information

Question 36

What device does the Edge QAM
communicate with for session setup
requests?

Answer 36

ERM( edge resource manager)