NeuStar Comments on NANC 301 CO

1. NeuStar Comments on NANC 301 CO Charles Green NeuStar, Inc. 8 March 2000

2. NeuStar Comments on NANC 301 CO • Description • “NPAC Monitoring of SOA and LSMS Associations via NPAC TCP Level Heartbeat” • Implementation by NPAC: • Apply HP/UX patch PHNE_17376 • enables support for TCP/IP heartbeats • Enable the transport layer keepalive feature on the OTS/RFC1006 stack • otsadm -k

3. NeuStar Comments on NANC 301 CO • Recommendation: • Service Providers enable TCP Keepalive feature • Implementation by SP: • Depends on OS • Typically option implemented by system administrator • Possibly requires an OS patch

4. NeuStar Comments on NANC 301 CO • Purpose: • Poll opposite end of idle connection to insure availability • Reduce duration of half-open connections • Reduce phantom associations • Cause aborts earlier than current detection of failures • Detects some failures, does not correct cause

5. NeuStar Comments on NANC 301 CO • Tunables • tcp_keepstart • “The number of seconds that a TCP connection can be idle (that is, no packets received) before keep-alive packets will be sent attempting to solicit a response. When a packet is received, keep-alive packets are not longer sent unless the connection is idle again for this period of time.” • HP/UX default 7200 (two hours) • NANC 301 recommends 60 (one minute)

6. NeuStar Comments on NANC 301 CO • Tunables • tcp_keepfreq • The interval in seconds at which keep-alive packets will be sent on a TCP connection once they have been started. The receipt of a packet will stop the sending of keep-alive packets. • If both tcp_keepfreq and tcp_keepstop are being increased, then tcp_keepstop should be increased first. If both are being decreased, then tcp_keepfreq should be decreased first. • HP/UX default 75 • NANC 301 recommends 60 (one minute)

7. NeuStar Comments on NANC 301 CO • Tunables • tcp_keepstop • The number of seconds keep-alive packets will be sent on a TCP connection without the receipt of a packet after which the connection will be dropped. • If both tcp_keepfreq and tcp_keepstop are being increased, then tcp_keepstop should be increased first. If both are being decreased, then tcp_keepfreq should be decreased first. • HP/UX default 600 (ten minutes) • NANC 301 recommends 60 (one minute)

8. NeuStar Comments on NANC 301 CO • tcp_keepstop • With default values (tcp_keepfreq = 75 and tcp_keepstop = 600): • “If TCP sends a total of 8 packets without receiving any response from the remote TCP (that is, after 10 minutes have passed), TCP drops the connection.” • Setting tcp_keepfreq equal to tcp_keepstop may result in abort if the first heartbeat response is not received. • NANC-recommended values may not permit retry to successfully maintain link. • NeuStar recommends tcp_keepstop be set to at least twice tcp_keepfreq to insure at least one retry.

9. NeuStar Comments on NANC 301 CO • tcp_keepstart • Keepalive packets from one side are seen as link activity from opposite side. • Setting tcp_keepstart equal on both sides of link could result in duplicate traffic with no benefit • SP implementation of keepalive feature will permit most timely response to link failure • SP must associate with NPAC, not vice versa • NeuStar recommends NPAC tcp_keepstart be set at least one minute larger than tcp_keepstart value used by SPs. • Predictable order of network events.