Transcript Document

Link Latency and R_A_TOV
4/8/04
With the addition of WAN links, R_A_TOV enforcement
made harder
 10
000 KM SONET = 50 ms
 10 000 KM TCP/IP = indeterminate
 FC-BB-2 added words:
Class F frames may be excepted from IP network transit
time checking; however all other classes of frames shall
have their IP network transit time computed and
checked. If a frame is found to have an IP network
transit time that would cause the frame.s lifetime in the
Fabric to exceed Fibre Channel requirements, the FC
Entity shall discard the frame.
It is difficult to know exactly how to build this!
2
Suggested fix

FSPF provides exchange of link information with
neighbors

In 6.1.9.4 of FC-SW-3, replace the reserved byte before
Link Cost with:
 Latency
bound; maximum transit time for the link,
including link-level recovery.
 0 = undefined.
 N => 2**N ns
 This allows specification of a range from ~.4m fibre to
(literally) astronomical distances.
 1 = 2 ns
 10 ~ 1 usec
 20 ~ 1 ms
 30 ~ 1 sec, etc.
3