Term
| What is Bc, Be and Tc?
interface s0/0
shape average 128000
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Definition
Because the rate is < 320 kbps, Bc=Be=8000 bits. Tc=Bc/rate = 62.5 msec. |
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Term
Given the configuration below, what is Bc and Tc?
interface s0/0
traffice-shape rate 1280000
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Definition
Because the rate is > 320000, Tc = 25 msec and Bc=rate*Tc = 32000. |
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Term
Name three advantages of CB traffic shaping over Generic Traffic Shaping |
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Definition
1) Fancing queuing in shaping queue (GTS only allows WFQ)
2) Fancing queuing in software interface queue
3) class-based shaping allows different kinds of traffic to be shaped at different rates |
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Term
With CB Traffic shaping, what are the default values for Tc, Bc and Be? |
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Definition
Same as Generic Traffic Shaping.
rate <= 320000, Bc=Be=8000, Tc=Bc/rate
rate > 320000, Tc=25 msec, Bc=rate * Tc |
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Term
With the following config, what is the actual shaping rate?
policy-map shape-all
class class-default
shape peak 96000 |
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Definition
By default Bc=Be=8000. For "shape peak", target rate = rate*(1+Be/Bc). Therefore, target rate is 192000 |
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Term
Given the following, what is shaping rate and Tc for int s0/0.1?
class MYCLASS
shape average percent 50 25 ms
int s0/0.1
service-policy output shape-all
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Definition
Default bandwidth is 1544, so the shaping rate will be .5 * 1544 = 772 kbps.
Tc=25 msec |
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Term
With the following config, what will the rate be after one packet with BECN set is received? After a second packet with BECN set?
policy-map shape-all
class MYCLASS
shape average 128000
shape adaptive 64000
int s0/0.1
service-policy output shape-all |
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Definition
After after one BECN, the rate is reduced by .25 *128000 to 96000. After the second packet, the rate is reduced again by .25*128000 to the minrate of 64000. |
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Term
Assume the following config. The traffic rate has been shaped down to 64000. Packets now arrive without BECNs. How long before the router resumes shaping at 128000?
policy-map shape-all
class MYCLASS
shape average 128000
shape adaptive 64000
int s0/0.1
service-policy output shape-all |
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Definition
After 16 good Tcs, the shaper will increase the rate by 1/16 each Tc. |
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Term
For the config below, what are Tc, Bc, and Be?
map-class frame-relay SHAPE
frame-relay traffic-rate 64000 96000
int s0/0
encap frame
frame-relay traffic-shaping
int s0/0.1
frame-relay class SHAPE
frame-relay interface-dlci 101 |
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Definition
FRTS defaults to Tc = 125 msec
Bc = Tc*CIR = 64000*.125 = 8000
Be = Tc * (PIR - CIR) = .125*32000 = 4000 |
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Term
For the config below, what are Tc, Bc, and Be?
int s0/0
encap frame
frame-relay traffic-shaping
int s0/0.1
frame-relay interface-dlci 101 |
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Definition
Tc = 125 msec
Bc = 7000
CIR = 56kbps
If no map-class frame-relay is configured, the above values are used as defaults. |
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Term
True or False: There is no way to set Bc or Be explicitly when using the frame-relay traffic-rate command. |
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Definition
False.
cir, Bc, and Be can be explicitly set using the following map-class syntax:
map-class frame-relay SHAPE
frame-relay cir 64000
frame-relay bc 8000
Tc is calcuated as Bc/CIR |
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Term
True or false? FRTS supports fancy queuing for packets in the shaping queue. |
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Definition
True. Fancy queuing can be enabled for the shaping queue by applying a queuing service-policy to the map-class.
map-class frame-relay SHAPE-WITH-LLQ
frame-relay cir 96000
frame-relay bc 960
service-policy output QUEUE-VOIP |
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Term
True or false? CB policing refills token buckets based on a time interval. |
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Definition
False.
CB policing replenishes bucket when a packet arrives based on (Time(now) - Time(previous packet) ) * police-rate / 8 |
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Term
In CB policing, one token represents how many bits? |
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Definition
In CB policing, one token = one byte = 8 bits. |
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Term
What kind of of policing is configured below?
policy-map POLICE-ALL
class class-default
police cir 96000 bc 12000 be 6000 conform-action transmit exceed-action set-dscp-transmit 0 violate-action drop |
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Definition
This is single rate (96000), 3 color (conform, exceed, violate). |
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Term
How many bits are in Bc and Be?
policy-map POLICE-ALL
class class-default
police cir 96000 bc 12000 be 6000 conform-action transmit exceed-action set-dscp-transmit 0 violate-action drop |
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Definition
cir = 96000 bps
Bc = 12000 bytes = 96000 bits
Be = 6000 bytes = 48000 bits
"Policing bytes bursts" |
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Term
| Can CB policing can be applied on the ingress or the egress of an interface or subinterface? |
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Definition
| Either ingress or egress. |
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Term
What is the value of Bc and Be?
policy-map POLICE-ALL
class class-default
police cir 96000 conform-action transmit exceed-action set-dscp-transmit 0 violate-action drop |
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Definition
Bc = CIR / 32 = 3000 (bytes!)
Be = Bc
If CIR / 32 < 1500, Bc = 1500. |
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Term
What kind of of policing is configured below?
policy-map POLICE-ALL
class class-default
police cir 96000 pir 128000 conform-action transmit exceed-action set-dscp-transmit 0 violate-action drop |
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Definition
Two Rate/Bucket, Three Color Policing |
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Term
How many tokens are added to which buckets when a packet arrives?
policy-map POLICE-ALL
class class-default
police cir 96000 pir 128000 conform-action transmit exceed-action set-dscp-transmit 0 violate-action drop |
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Definition
Bc = 96000/ 32 = 3000
Be = 128000/32 = 4000
Tokens in Bc bucket = (Tnow - Tlast) * CIR / 8
Tokens in Be bucket = (Tnow - Tlast) * PIR / 8 |
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Term
What type of policier uses the following defaults:
Bc = CIR/32
Be = 0 |
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Definition
Class-based, single-rate two color (conform and exceed) |
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Term
What type of policier uses the following defaults:
Bc = CIR/32
Be = CIR/32 |
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Definition
Class-based single rate, three color (conform, exceed, violate). |
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Term
What type of policier uses the following defaults:
Bc = CIR/32
Be = PIR/32 |
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Definition
Class-based dual-rate (cir, pir), three color policer (conform, exceed, violate). |
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Term
True or false: CB policing supports multi-action policing. |
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Definition
True. See config below.
policy-map POLICE-ALL
class class-default
police 128000
conform-action transmit
exceed-action transmit
violate-action set-dscp transmit 0
violate-action set-frde-transmit |
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Term
How many rates/colors does CAR support? |
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Definition
Single-rate, two color (conform, exceed). |
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Term
What does this accomplish and where would it be configured?
rate-limit input access-group 101 20000000 24000 32000 conform-action set-prec-transmit 5 exceed-action set-prec-transmit 0 |
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Definition
This is CAR. It's applied at the interface (input or output). The policing rate is 20 Mb, with Bc=24000 bytes and Be=32000 bytes.
interface f0/0
rate-limit input access-group 101 20000000 24000 32000 conform-action set-prec-transmit 5 exceed-action set-prec-transmit 0
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Term
| what kind of traffic shaping can learn CIR, Bc and Be dynamically? |
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Definition
| FRTS can learn CIR, Bc, and Be from ELMI |
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Term
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Definition
| On the main physical interface. |
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Term
| If no parameters are specified, what values does FRTS use? |
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Definition
rate = 56k
Bc = 7000 bits
Tc = 125 msec |
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Term
what does the following do:
frame-relay de-list 1 protocol ip gt 1500
interface serial2/0
frame-relay de-group 1 200 |
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Definition
| Sets DE bit for IP packets > 1500 bytes on DLCI 200. |
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Term
What kind of shaping is configured below and what are Bc and Be?
traffic-shape rate 128000 |
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Definition
Generic traffic shaping.
If not specified, Bc = Be = .25 * rate = 32000 |
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Term
What kind of traffic shaping is this and what are Bc and Be?
traffic-shape rate 128000 |
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Definition
Generic traffic shaping.
With GTS, Bc = Be = .25 * rate if not specified. |
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Term
| What are the defaults for BC, Be and Tc for CB TS, FRTS and GTS? |
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Definition
CBTS: for rate <= 320kbps, Bc = Be = 8000, Tc = Bc/rate
for rate > 320kbps, Tc = 25ms
FRTS: (rate only config) Tc = 125 msec, Bc = CIR * Tc, Be = (PIR-CIR) * Tc
...or set Bc directly and Be defaults to 0
GTS: Bc = Be = rate / 4 |
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