|
North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: T1 Circuit actual throughput 1290Kbps
In message <[email protected]>, Tony S. Hariman writes: >Does anybody have experience having a T1 circuit with PPP >encapsulation getting only 1290 Kbps maximum throughput looking >at "sh int" result from cisco router or MRTG ? A T1 is capable of achieving 1536 kbps maximum (24 x 64 kbps). typically, the output shown both via snmp interface-counters and from a cisco "show int" includes all of the associated PPP framing. bear in mind that the output of a "show int" by default shows a 5-minute-exponentially-decayed average of the throughput. this will 'smooth' out instantaneous traffic bursts and troughs. the figure reported as a 'kbps' figure is most likely bursting much higher than this. >This is the explanation our upstream provider gave us: > >You have a 1.536Mbps port. However, there is the overhead from >PPP and the translation overhead which takes place in all circuits. >Judging by your settings that limit ends up somewhere between >1.3 and 1.4. This overhead would be the non-data portion of cells >or frames for example. For example, you might have 1.3 Mbps of >data which gets framing or cell information appended onto it before >sending taking up additional bandwidth. It is to be expected in all >circuits. PPP doesn't have much of the overhead of IP-in-ATM-cells (fixed-cell-size, very-badly-chosen-prime-number-cell-size, ..) that the discussion given to you by your upstream is talking about. what kind of traffic are you sending over the link ? perhaps there isn't enough traffic / the traffic isn't of the variety to actually fill the link capacity. if its mostly TCP traffic, don't expect it to fill the whole pipe all the time. cheers, lincoln.
|