Path: utzoo!utgpu!water!watmath!clyde!rutgers!mcnc!uvaarpa!umd5!hans
From: hans@umd5.umd.edu (Hans Breitenlohner)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: MILNET/?/UMDNET/SURA/GWU-GATE traffic question
Message-ID: <2195@umd5.umd.edu>
Date: 13 Jan 88 19:02:13 GMT
References: <8801052325.AA00729@sneezy.lanl.gov>
Reply-To: hans@umd5.umd.edu (Hans Breitenlohner)
Organization: University of Maryland, College Park
Lines: 79

This is an attempt to explain some of the strangeness which was reported
in and around SURA-net land.
As far as I can tell from the fragments of information, the packet 
traversed the following path:
        milnet-gw.lanl.gov             26.0.0.90
                                         Milnet                  ???
        some milnet to arpa gateway
                                         Arpanet                  56 kb serial
        umd.umd.edu/trantor.umd.edu    10.8.0.20/128.8.10.14
                                         UMD subnet 128.8.10      Ether
        bogon-gw.umd.edu               128.8.10.41/129.2.1.1
                                         UMD-BOGON-NET 129.2      Ether
        sura1 gateway at U of Md       129.2.1.2/128.167.1.1
                                         SURA subnet 128.167.1    Ether
        sura2 gateway at U of Md       128.167.1.2/128.167.2.1
                                         SURA subnet 128.167.2    56 kb serial
        sura gateway at George Washington 128.167.2.2/128.164.1.1
                                         GWU campus net           Ether
        gwuvm.gwu.edu                  128.164.1.234
>
> so far, so good
>
                                         GWU campus net           Ether
        sura gateway at GWU            128.164.1.1/128.167.2.2
                                         SURA subnet 128.167.2    56 kb serial
        sura2 gateway at U of Md       128.167.2.1/128.167.1.2
                                         SURA subnet 128.167.1    Ether
        sura1 gateway at U of Md       128.167.1.1/128.167.33.1
                                         SURA subnet 128.167.33   56 kb serial
        sura gateway at NRL            128.167.33.2
                                         SURA subnet 128.167.33   56 kb serial
        sura1 gateway at U of Md       128.167.33.1
>
> and so on, ad infinitum (or nearly so) between sura1 and sura-NRL.
>
Trantor is a Vax running 4.3 BSD.  Bogon-gw, sura1 and sura2 are Proteon
p4200 routers running release 7.4 of their software, which honors the
'record route' option.  The remaining sura gateways are Proteon p4200
routers running release 7.3 of their software, which ignores the 'record route'
option.  This shows the usefulness of this IP option, and makes us wish more
software packages would honor it.

The following is educated guesswork, since I never got to see things in this
state, and since I do not have access to gateways outside the University of
Maryland.  Apparently the gateway at NRL was advertising net 26 reachability
with a small hop count.  There was a static route configured in it,
and routing and advertising are not easily separated in that software.
This is a bad situation at any time, and for several reasons.  Apparently
it was aggravated by local Ethernet problems at NRL, which caused the gateway
to decide that the Ethernet was down, and send the packet to its default
network gateway, which was pointing back to sura1 at U of Md.

The fact that the packet arrived at all is likely a result of NRL's ethernet
problems being transient, or of the fact that the routing information between
the two gateways got straightened out and the packet was returned along the
route by which it was sent out.  Since no date/time was given with the
problem report it is hard to verify any of this.

This seems adequate to explain the extraordinary delays and the packet loss
reported.  I am at a loss to explain the duplicated packets.  Perhaps someone
else can help out with that.

The problem has been resolved, and traffic between SURA-net and Milnet should
perform much better now.  The sura1 gateway will no longer believe
net 26 advertisements from NRL, and I understand that the static route will
also be removed from the gateway there.  Ironically this is a leftover from
past attempts by various other groups to confine Milnet traffic to their
local connections.  

Thanks to cpw for reporting the problem and providing useful information.

In a case like this, where the problem was clearly confined to one net 
(128.167) it would likely be faster and more effective to contact the
administrator of the net in question directly.  The necessary information
can be obtained using the 'whois' utility (as in 'whois 128.167.0.0').
For more information on it and other services provided by the NIC you might
want to get a copy of "DDN NEW USER GUIDE", Publication # NIC 50001.  If you
can not get it through your network administrator, use the NIC's toll free
phone number 800-235-3155 to order one.