Possible causes of slow network file transfer when PXE booting

Products

• Ghost Solution Suite
• Deployment Solution

Issue/Introduction

When increasing the packet size for the MTFTP the file transfer slows down

Environment

GSS 3.3.x

DS 8.x

Resolution

Increasing packet size in a network doesn't always translate to increased speed because of factors like fragmentation, latency, and buffer limitations. While larger packets can potentially reduce header overhead and increase throughput, excessively large packets can lead to fragmentation, which adds overhead and latency. Additionally, network devices and links may have maximum transmission unit (MTU) sizes that limit the maximum packet size, and smaller packets can be processed faster by network equipment. 

 

Here's a more detailed explanation:

 

1. Fragmentation:

• If a packet exceeds the MTU of a network link, it will be fragmented into smaller packets. 
   
• Fragmentation adds extra processing time for both the sending and receiving devices, and it can also increase the risk of packet loss and retransmission. 
   
• Therefore, while large packets can increase throughput, they can also lead to performance degradation if they cause fragmentation. 
   

2. Latency and Buffering:

• Network devices store and forward packets, and larger packets take longer to process and transmit.
• This can increase latency and potentially lead to buffer overflow issues on network equipment.
• Additionally, if a packet is lost or damaged, the entire larger packet needs to be retransmitted, which can waste bandwidth. 
   

3. Network Equipment and Links:

• Switches, routers, and other network equipment process packets on a per-packet basis. 
   
• While larger packets may reduce the number of packets to be processed, they also require more processing time per packet. 
   
• Some network links may not be able to handle very large packets, and they may fragment them or simply drop them. 
   
• Network equipment may also have limitations on the number of packets they can process simultaneously, especially for smaller packets. 
   

4. Bandwidth and Throughput:

• Larger packets can increase bandwidth utilization by reducing the overhead of headers. 
   
• However, excessive fragmentation can negate this benefit and even decrease bandwidth utilization. 
   
• The optimal packet size depends on the specific network environment and the characteristics of the connection. 
   

5. TCP/IP and Window Size:

• TCP/IP uses a window size to control the amount of data that can be sent at a time.
• Increasing the window size can improve throughput, but it can also increase the risk of packet loss if the network is congested.
• The optimal window size depends on factors like latency and bandwidth.