PowerMax and VMAX All Flash Solutions Design (Gigabit Ethernet and IP Considerations)

Question 1

What is a TCP Window?

Answer 1

the amount of data a sender can send without waiting for an Acknowledgement from the receiver

ensures no congestion occurs in the network

Question 2

What is the typical allocation of a TCP window header?

Answer 2

16 bits for window advertisement

limits the maximum window to be 64KB without window scaling

Question 3

What is window scaling?

Answer 3

allows windows to be more than 64KB

expands the definition of the window to 32 bits

Question 4

How many MTU are a standard Ethernet packet?

Answer 4

1500 MTU

can get up to 9000 MTU

Question 5

What is MTU?

Answer 5

maximum transmission unit

the largest TCP packet size that can be sent across the network without the packet being fragmented

Question 6

What are Jumbo Frames?

Answer 6

packets larger than 1500 MTU but less than 9000 MTU

Question 7

What is an effect of packet fragmentation?

Answer 7

can cause packet loss and severe loss in throughput

Question 8

How can packet fragmentation have a negative effect on throughput?

Answer 8

packets may not be reassembled or packets may be dropped

can cause a high processor load on the device performing the fragmentation

Question 9

How do you prevent fragmentation?

Answer 9

verify that every device in the network path has the same MTU value set

Question 10

What is the latency recommendation for SRDF/S?

Answer 10

maintain latency between SRDF/S ports within 5ms round trip time (RTT)

packet loss should not exceed 0.01% for SRDF/S and 0.1% for SRDF/A

Question 11

What is latency jitter?

Answer 11

used to refer to the variation in latency of packet flow from endpoint to endpoint

should be as low as possible

Question 12

What is best practice for latency jitter?

Answer 12

variance in latency should not exceed 25% of the average network latency or 25ms

Question 13

What can mitigate the problems of high latency and fragmentation for Ethernet replication?

Answer 13

use of WAN optimization devices

can maximize the amount of data that can be transmitted over a link - should be one on each side

Question 14

How is increased performance achieved with WAN optimization devices?

Answer 14

increasing window sizes

more efficient block streaming protocols

caching of data

Question 15

What is important to maximize Ethernet replication performance?

Answer 15

important that all Ethernet ports on primary and secondary array can see each other across the network

remote replication throughput scales w/ TCP connections

Question 16

What MTU settings should you have implemented when using SRDF?

Answer 16

GbE director should support jumbo frames