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what is (SYN, ECN, CWR) seen in SYN packet ?

asked 2022-07-29 06:38:23 +0000

Rajessh gravatar image

updated 2022-07-29 09:59:40 +0000

hi all,

i found out that the syn packet from the source to destination has (SYN, ECN, CWR),i dont knon what is the exact root cause. i have done some research adn found out that it could be the problem regarding the bandwidth congestion. any help please

from source to destination [ TCP 52 1460 8192 8192 62718 → 7002 [SYN, ECN, CWR] Seq=0 Win=8192 Len=0 MSS=1460 WS=256 SACK_PERM=1]

Thank you!

regards, Rajesh

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answered 2022-07-29 12:52:19 +0000

Jaap gravatar image

This is used during the establishment on a TCP connection to signal that the initiating TCP endpoint is willing and capable of handling Explicit Congestion Notification for this connection, see here. Depending on the rest of the connection establishment ECN can be used or not.

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hello jaap,

well thanks for you answer, but i have some other question... i analyzed the 3-way handshake packets there i noticed that the other server side has no TCP option for window scaling... could it be the reason that the other server has got very small TCP buffer size ??

Internet Protocol Version 4, Src:, Dst: Transmission Control Protocol, Src Port: 62718, Dst Port: 7002, Seq: 0, Len: 0 Source Port: 62718 Destination Port: 7002 [Stream index: 0] [TCP Segment Len: 0] Sequence Number: 0 (relative sequence number) Sequence Number (raw): 830838424 [Next Sequence Number: 1 (relative sequence number)] Acknowledgment Number: 0 Acknowledgment number (raw): 0 1000 .... = Header Length: 32 bytes (8) Flags: 0x0c2 (SYN, ECN, CWR) Window: 8192 [Calculated window size: 8192] Checksum: 0x2977 [unverified] [Checksum Status: Unverified] Urgent Pointer: 0 Options: (12 bytes), Maximum segment size, No-Operation (NOP), Window scale ...(more)

Rajessh gravatar imageRajessh ( 2022-07-31 09:21:23 +0000 )edit

A different question, so should be posted as such.

Jaap gravatar imageJaap ( 2022-07-31 12:45:09 +0000 )edit

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Asked: 2022-07-29 06:38:23 +0000

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Last updated: Jul 29 '22