📄 rfc827.txt
字号:
0 Unspecified
1 Going down
2 No longer needed
Otherwise, this field MUST be zero.
Identification Number
An identification number to aid in matching requests and
replies.
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RFC 827 Bolt Beranek and Newman Inc.
Eric C. Rosen
NEIGHBOR HELLO/I HEARD YOU MESSAGE
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! EGP Version # ! Type ! Code ! Status !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Checksum ! Autonomous System # !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Sequence # !Min Poll Intvl ! Zero !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Last Poll Id # !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Description:
Exterior neighbors use EGP Neighbor Hello and I Heard You
Messages to determine neighbor connectivity. When a gateway
receives an EGP Neighbor Hello message from a neighbor it
should respond with an EGP I Heard You message.
EGP Version #
1
Type
5
Code
Code = 0 for Hello
Code = 1 for I Heard you
Checksum
The EGP checksum is the 16-bit one's complement of the one's
complement sum of the EGP message starting with the EGP
version number field. For computing the checksum, the
checksum field should be zero.
Autonomous System #
This 16-bit number identifies the autonomous system
containing the gateway which is the source of this message.
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RFC 827 Bolt Beranek and Newman Inc.
Eric C. Rosen
Sequence Number
A sequence number to aid in matching requests and replies.
Status
0 No status given
1 You appear reachable to me
2 You appear unreachable to me due to neighbor
reachability protocol
3 You appear unreachable to me due to network
reachability information (such as 1822 "destination
dead" messages from ARPANET)
4 You appear unreachable to me due to problems
with my network interface
Last Poll Id Number
The identification number of the most recently received
NR poll message from the neighbor to which this message
is being sent.
Minimum Polling Interval
This gateway should not be polled for NR messages more
often than once in this number of minutes.
- 36 -
RFC 827 Bolt Beranek and Newman Inc.
Eric C. Rosen
NR POLL Message
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! EGP Version # ! Type ! Code ! Unused !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Checksum ! Autonomous System # !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! IP Source Network ! Interval !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Identification # !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Description:
A gateway that wants to receive an NR message from an
Exterior Gateway will send an NR Poll message. Each gateway
mentioned in the NR message will have an interface on the
network that is in the IP source network field.
EGP Version #
1
Type
2
Code
0
Checksum
The EGP checksum is the 16-bit one's complement of the one's
complement sum of the EGP message starting with the EGP
version number field. For computing the checksum, the
checksum field should be zero.
Autonomous System #
This 16-bit number identifies the autonomous system
containing the gateway which is the source of this message.
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RFC 827 Bolt Beranek and Newman Inc.
Eric C. Rosen
Identification Number
An identification number to aid in matching requests and
replies.
IP Source Network
Each gateway mentioned in the NR message will have an
interface on the network that is in the IP source network
field. The IP source network is coded as one byte of
network number followed by two bytes of zero for class A
networks, two bytes of network number followed by one byte
of zero for class B networks, and three bytes of network
number for class C networks.
Interval
The polling interval in minutes.
- 38 -
RFC 827 Bolt Beranek and Newman Inc.
Eric C. Rosen
NETWORK REACHABILITY MESSAGE
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! EGP Version # ! Type ! Code !U! Zeroes !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Checksum ! Autonomous System # !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Fragment # !# of last frg. ! Identification # !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! IP Source Network !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! # of Int Gwys ! # of Ext Gwys !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! # of Nets ! ; # of nets for
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Gateway 1
! Gateway 1 IP address (without network #) ! ; 1, 2 or 3 bytes
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! net 1,1 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ; 1, 2 or 3 bytes
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! distance !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! net 1,2 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ; 1, 2 or 3 bytes
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! distance !
+-+-+-+-+-+-+-+-+
.
.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! net 1,m !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ; m nets reachable
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ; via Gateway 1
.
.
+-+-+-+-+-+-+-+-+
! # of nets ! ;number of nets for Gateway n
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Gateway n IP address (without network #) !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! net n,1 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ; 1, 2 or 3 bytes
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! distance !
+-+-+-+-+-+-+-+-+
- 39 -
RFC 827 Bolt Beranek and Newman Inc.
Eric C. Rosen
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! net n,2 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ; 1, 2 or 3 bytes
+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! distance ! .
+-+-+-+-+-+-+-+-+ .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! net n,m !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ; m nets reachable
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ; via Gateway n
! distance !
+-+-+-+-+-+-+-+-+
- 40 -
RFC 827 Bolt Beranek and Newman Inc.
Eric C. Rosen
Description:
The Network Reachability message (NR) is used to discover
which networks may be reached through Exterior Gateways. The NR
message is sent in response to an NR Poll message.
EGP Version #
1
Type
1
Code
0
Checksum
The EGP checksum is the 16-bit one's complement of the one's
complement sum of the EGP message starting with the EGP
version number field. For computing the checksum, the
checksum field should be zero.
Autonomous System #
This 16-bit number identifies the autonomous system
containing the gateway which is the source of this message.
U (Unsolicited) bit
This bit is set if the NR message is being sent unsolicited.
Identification Number
The identification number of the last NR poll message
received from the neighbor to whom this NR message is being
sent. This number is used to aid in matching polls and
replies.
Fragment Number
Which Fragment this is in the NR Message. Zero, if
fragmentation is not used.
- 41 -
RFC 827 Bolt Beranek and Newman Inc.
Eric C. Rosen
Number of Last Fragment
Number of the last fragment in the NR Message. Zero, if
fragmentation is not used.
IP Source Network
Each gateway mentioned in the NR message will have an
interface on the network that is in the IP source network
field.
# of Interior Gateways
The number of interior gateways that are mentioned in this
message.
# of Exterior Gateways
The number of exterior gateways that are mentioned in this
message.
# of Networks
The number of networks for which the gateway whose IP
address immediately follows is the appropriate first hop.
Gateway IP address
1, 2 or 3 bytes of Gateway IP address (without network #).
Network address
1, 2, or 3 bytes of network address of network which can be
reached via the preceding gateway.
Distance
1 byte of distance in # of hops.
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