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I am seeing veeeeeerry slow feedback on remote ssh terminals to a new install of Ubuntu 16.04. E.g., after typing a character it may take 20-30 seconds before it is displayed in the terminal. Initial login with password to the server is fast, just subsequent keyboard entry is slow. Other applications (mysql, nginx) show good performance, so this seems to only affect ssh.

The server is on the local network, and ping latency client->server and server->client varies between 1ms and 300ms depending on traffic, so network latency is not the cause of the delays. Traceroute shows no issues.

The server is not busy, and local sessions have good performance, so server resources are not the cause of the delays.

I have tried adding entries to hosts files on both client and server. I have tried switching the client from DHCP to static IP/gateway/DNS. I tried with ssh -v (below) and also ssh -C.

I'm looking for suggestions on how to debug this issue and get ssh terminal performance back to a usable level. Any suggestions welcome.

Roberts-MacBook-Pro:~ regeier$ ping 192.168.1.111
PING 192.168.1.111 (192.168.1.111): 56 data bytes
64 bytes from 192.168.1.111: icmp_seq=0 ttl=64 time=2.565 ms
64 bytes from 192.168.1.111: icmp_seq=1 ttl=64 time=2.184 ms
64 bytes from 192.168.1.111: icmp_seq=2 ttl=64 time=2.259 ms
^C
--- 192.168.1.111 ping statistics ---
3 packets transmitted, 3 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 2.184/2.336/2.565/0.165 ms
Roberts-MacBook-Pro:~ regeier$ ssh -v ubuntu@192.168.1.111
OpenSSH_6.9p1, LibreSSL 2.1.8
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 21: Applying options for *
debug1: /etc/ssh/ssh_config line 56: Applying options for *
debug1: Connecting to 192.168.1.111 [192.168.1.111] port 22.
debug1: Connection established.
debug1: identity file /Users/regeier/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/regeier/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/regeier/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/regeier/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/regeier/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/regeier/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/regeier/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/regeier/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.9
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2p2 Ubuntu-4ubuntu2.1
debug1: match: OpenSSH_7.2p2 Ubuntu-4ubuntu2.1 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 192.168.1.111:22 as 'ubuntu'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client chacha20-poly1305@openssh.com <implicit> none
debug1: kex: client->server chacha20-poly1305@openssh.com <implicit> none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:2v5V8cSY2r2DLlfxdNJ6M1zw0yk467wLQiUof0/t1so
debug1: Host '192.168.1.111' is known and matches the ECDSA host key.
debug1: Found key in /Users/regeier/.ssh/known_hosts:4
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /Users/regeier/.ssh/id_rsa
debug1: Authentications that can continue: publickey,password
debug1: Trying private key: /Users/regeier/.ssh/id_dsa
debug1: Trying private key: /Users/regeier/.ssh/id_ecdsa
debug1: Trying private key: /Users/regeier/.ssh/id_ed25519
debug1: Next authentication method: password
ubuntu@192.168.1.111's password: 
debug1: Authentication succeeded (password).
Authenticated to 192.168.1.111 ([192.168.1.111]:22).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug1: Sending environment.
debug1: Sending env LANG = en_AU.UTF-8
Welcome to Ubuntu 16.04.1 LTS (GNU/Linux 4.4.0-31-generic x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage

0 packages can be updated.
0 updates are security updates.


Last login: Fri Jan 27 20:47:02 2017 from 192.168.1.3
  • In different window (or on server) try to find out possible networking problems with tcpdumpor wireshark – ridgy Jan 27 '17 at 12:53
  • Is it a raspberry pi server? – dedunumax Jan 27 '17 at 12:57
  • Server is HP Z600. 2 x quad core AMD. – Robert Jan 27 '17 at 12:59

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