network
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... EGP provides a means for different autonomous gateway systems to exchange
information about the networks that are reachable via them.
This report mainly describes an implementation of EGP ...
... Newman (BBN) and many "stub" AS's that are maintained by different
organizations and have at least one network in common with a core AS gateway.
...
... routing gateway
to the University of California at Irvine network (UCI-ICS). With the
elimination of non-routing ...
... gateway would need to convey routing
information via EGP. Details of the ISI network configuration are discussed in
Section 5.2.
...
... just responds is in the passive mode.
Network reachability is determined by periodically sending Poll commands and
receiving Update responses which indicate the ...
... is determined by periodically sending Poll commands and
receiving Update responses which indicate the networks reachable via one or
more gateways on the shared network ...
... networks reachable via one or
more gateways on the shared network. Currently 2 minute minimum interval is
used across ARPANET.
...
... A route consists of a destination network number, the address of the next
gateway to use on a directly connected ...
... number, the address of the next
gateway to use on a directly connected network, and a metric giving the
distance in gateway hops to the destination ...
... EGP process tables. The kernel has separate tables for host
and network destinations. The EGP process only maintains the network ...
... network destinations. The EGP process only maintains the network routing
tables. The EGP tables are updated when EGP ...
... Update messages are received. When
a route is changed the kernel network tables are updated via the SIOCADDRT and
SIOCDELRT ioctl system calls. At initialization the kernel network ...
... network tables are updated via the SIOCADDRT and
SIOCDELRT ioctl system calls. At initialization the kernel network routing
tables are read via the kernel memory image file, /dev/kmem, and copied into
...
... - No routing table entry exists for the destination network and the
metric indicates the route is reachable (< 255).
...
...
Outgoing Updates include the direct and static networks from the interior
routing table, except for the network shared with the ...
... Outgoing Updates include the direct and static networks from the interior
routing table, except for the network shared with the EGP neighbor.
...
... neighbor.
The networks that are allowed to be advised in Updates may be specified at
initialization in EGPINITFILE. This allows particular routes to be excluded
from exterior updates in cases where ...
... If the interior routing table includes other interior gateways on the network
shared with the EGP neighbor ...
... EGP neighbor they are include in Updates as the appropriate
first hop to their attached networks.
The distance to networks ...
... networks.
The distance to networks is set as in the interior routing table except if the
route is marked down in which case the distance is set to 255. At present
...
... gateway and normal operation to automatically resume
from this gateway without an excess of unnecessary network traffic.
The actual Hello and Poll intervals are chosen by first selecting the maximum
...
... of the intervals advised by this gateway and its peer. A 2 second margin is
then added to the Hello interval to take account of possible network delay
variations and the Poll interval is increased to the next integer ratio of the
...
... unreachable neighbor is ceased and reacquisition attempted every 4 minutes.
This is aimed at reducing unnecessary network traffic.
If valid ...
... At most one repoll (same sequence number) received before the poll interval has
expired (less a 4 second margin for network delay variability) is responded to
with an Update, others are sent an Error response ...
... synchronization has probably been
lost for some reason. A Cease(protocol violation) message is sent to try and
reduce unnecessary network traffic. This action is an option in [Mills84a].
...
... if there is no specific
route for the destination network. This provides a final level of backup if all
known EGP neighbors ...
... is one area where the slow response of EGP polling could be improved. This is
of particular interest to networks that may be connected by dial-in lines.
When such a network ...
... networks that may be connected by dial-in lines.
When such a network dials in, its associated interface will be marked as up but
it will not be able to receive packets until the change has been propagated by
...
... Network Level Status Information ...
...
Considering the general trend to increased network interconnection and the
availability of alternative long-haul networks such as ARPANET ...
... Considering the general trend to increased network interconnection and the
availability of alternative long-haul networks such as ARPANET, WBNET (wideband
satellite network), and public data ...
... availability of alternative long-haul networks such as ARPANET, WBNET (wideband
satellite network), and public data networks the tree topology ...
... such as ARPANET, WBNET (wideband
satellite network), and public data networks the tree topology restriction is
...
... autonomous system consists of a set of gateways connected by
networks. Each gateway in the system must be reachable from every
other gateway ...
...
A simplified version of the ISI network configuration is shown in Figure 5-1.
ISI-Hobgoblin can provide a backup gateway function to the core ISI-Gateway ...
...
ISI-Troll is part of a split gateway to the University of California at Irvine
network (UCI-ICS). The complete logical gateway consists of ISI-Troll, the 9600
...
... route entries indicating
ISI-Gateway as the first hop for all networks other than UCI-ICS and ISI-NET.
...
... ----------------------
Figure 5-1: Simplified ISI Network Configuration
...
... only ever know about the alternative route from the shared EGP network and not
from the other network. Thus a loop cannot occur. For instance, if EGP ...
... EGP network and not
from the other network. Thus a loop cannot occur. For instance, if EGP is
conducted over ISI-NET, both ISI-Gateway ...
... the extra hop via ISI-Gateway for packets originating from ISI-Hobgoblin, as a
host, and destined for exterior networks.
This configuration change ...
... The aim is to be able to detect when the primary gateway is down and have all
hosts on the local network change to the backup gateway with a minimum amount
of additional network traffic ...
... network change to the backup gateway with a minimum amount
of additional network traffic. The hosts should revert back to the primary
gateway when it comes up again.
...
... Mills, D.L., "Exterior Gateway Protocol Formal Specification", Network Information Center RFC 904hist, April 1984. ...
... Postel, J., "Exterior Gateway Protocol Implementation Schedule" Network Information Center RFC 890, Feb. 1984. ...
... Seamonson, L.J. and Rosen, E.C., "Stub Exterior Gateway Protocol", Network Information Center RFC 888, Jan. 84. ...