| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 3600.1 | remove FDDI bridging | MARVIN::RIGBY | No such thing as an alpha beta | Fri Apr 11 1997 07:56 | 20 |
| >I updated a DECnis with V4.0.2 and the PPP connection to a Routeabout
>router would not come up. I then reconfigured the DECnis and removed bridging
>and everthing came up fine.
My guess from this restricted information was that the SDU size on the bridge
port and the PPP link was 4500 and RouteAbout can't receive packets that big and
would thus reject the LCP configuration.
I would suggest adding
REMOVE BRIDGE PORT ppplinkport MAC TYPES {FDDI}
SET BRIDGE PORT ppplinkport MANUAL DATA LINK SDU SIZE 1524
SET PPP LINK ppplink PREFERRED MAXIMUM RECEIVE SDU SIZE 1524, MINIMUM SDU SIZE 1524
to the extra SET ncl file.
>Funny thing, IP was down as well, not only bridging. My downtime window was
>not wide enough to troubleshoot, so I can't tell if LCP was up, or IPCP.
John
|
| 3600.2 | Why reject the LCP MRU negociated size of 1500 | KAOFS::HXMP01::p_savoie | mcs network support | Fri Apr 11 1997 14:37 | 8 |
| Hi John,
In regards to your reply, it makes sense, and it will probably fix it, but
considering the fact that I did not have any FDDI module, and even if I did,
it does not seem reasonable to set(not negociate) a 4500 MTU size. Worst case
it should have accepted the smaller value proposed back by the RouteAbout,
assuming that LCP negociation works.
Regards
|
| 3600.3 | design changes required and planned | MARVIN::RIGBY | No such thing as an alpha beta | Mon Apr 14 1997 09:14 | 18 |
| We have a design change in progress to improve the PPP packet size negotiation
to try to get more interworking connections to work without manual intervention
in 'tuning' the SDU size.
It is not as easy as it looks, the size is negotiated at LCP start time so
adding a new client later which has a larger SDU requirement is impossible.
Further, the default size is 1500, which is right for IP but insufficient for
bridged traffic (You can't fit a 1518 byte ethernet packet + the 6 bytes of
RFC1220 bridge header into 1500 bytes). Even worse, the BRIDGE mac types
negotiation, performed by the BRGCP, has implications for the SDU size too, or
vice-versa and our implementation doesn't have the right feedback between the
bridge layer and the PPP layer.
The worst problem is over Frame Relay where the 'datalink' is really shared
between PPP and FrameRelay. PPP might happily negotatiate 4500 byte SDU but the
underlying fabric (the FR network) might be unable to support it.
John
|