11/14/2022 0 Comments Wireshark http and tcpIt signals when there is more data as well as the last DATA frame. In another test ( http2-v2.zip) I used HTTP/2 GET request instead of HEAD and requested more data which comes in through DATA frame type:Įnd Stream flag is false in all DATA messages except for the last one. WINDOW_UPDATE just adjusted this value to 1073676289: If you look at section 3 above we see that Client advised BIG-IP that its Initial Window Size was 1073741824. There are other common frame types and in my capture the one that came up was WINDOW_UPDATE. Appendix A - Other common frame types 5.1 WINDOW_UPDATE If there was payload it would be carried inside DATA frame type but as this is just a HEAD request then no DATA frame follows.ĥ. For HTTP/2 GET/HEAD requests there is a specific frame type called HEADERS which as the name implies carries HTTP/2 header information. Yes, Magic frame is always the same.Įnd-points are also supposed to ACK the receipt of SETTINGS frame from the other peer and the way they do it is by responding with another empty SETTINGS frame with ACK flag set:Ĭonnection-wise we're all set now. #Wireshark http and tcp plus#Server side (BIG-IP in this case) sends SETTINGS frame which counts as confirmation that HTTP/2 is being used plus any flow control configuration we want our peer to honour:Ĭlient sends Magic frame to confirm HTTP/2 is being used and then SETTINGS with its requirements for the connection. Think of it as something that has to take place like Client Hello and Server Hello in SSL for example. HTTP/2 is negotiated during SSL handshake in Application Layer Protocol Negotiation ( RFC 7301) SSL extension like this:Ĭlient says which protocol(s) it supports and server responds which one it picked (in this case it's HTTP/2!). Here's packet capture (in case you want to follow along): http2-test-v1.zip Note: 10.199.3.44 is my virtual server with HTTP/2 profile applied. The packet capture taken below was the result of the following curl command issued from my ubuntu Linux client (I could've used a browser instead): Confirmation of which protocol will be used I'll just issue a HEAD request and later on a GET request and we'll see how it looks like on Wireshark.įor more info about HTTP/2 profile and HTTP/2 protocol itself you can read the article I published on AskF5 and Jason's DevCentral article: What is HTTP Part X - HTTP/2. It's a simple test and here's the topology: It turns out Wireshark is a perfect tool for me to do just that. We can turn this feature off via ethtool -K eth0 gso offĪfter turning it off, if you take another capture, wireshark will display what you expect indeed.Some people find it easier to do a "test drive" first to learn how a new protocol works in its simplest form and only then read the RFC. We can display current setting for tso/gso ethtool -k eth0 TSO is definitely an improvement on host resource usage but for demonstration and testing it really makes things difficult. However if segmentation is handed over to network adapter, host machine instead of doing segmentation itself, it sends chunk of segment to network adapter for segmentation at which wireshark captures this transmission and displays a header length which you don’t expect. Normally TCP segmentation is handled by the host CPU with which wireshark displays reasonable lengths. I asked myself how could that happen? A little search showed that it is because of segmentation offload in the network adapter. Have a look at total length field of this IP packet. Maybe one screenshot is more than many words While I was trying to troubleshoot some TCP communication, I wanted to investigate something which I have ignored so far. Before reading this post you may have a look at the link which is the main motive of this post.
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