📄 rfc2353.txt
字号:
Dudley Informational [Page 16]
RFC 2353 APPN/HPR in IP Networks May 1998
*------------------------------------------------------------------*
|CS DLC LDLC DMUX UDP|
*------------------------------------------------------------------*
. . . .
.CONNECT_OUT(RQ) . create . .
o--------------->o-------------->o . .
. | new LDLC . .
. o----------------------------->o .
CONNECT_OUT(+RSP)| . . .
o<---------------* . . .
| XID . XID(CMD) . XID
*------------------------------->o----------------------------->o----->
Figure 3. Regular TG Activation (outgoing)
In Figure 3 upon receiving START_LS(RQ) from NOF, CS starts the link
activation process by sending CONNECT_OUT(RQ) to the DLC manager.
The DLC manager creates an instance of LDLC for the link, informs the
link demultiplexor, and sends CONNECT_OUT(+RSP) to CS. Then, CS
starts the activation XID exchange.
*------------------------------------------------------------------*
|CS DLC LDLC DMUX UDP|
*------------------------------------------------------------------*
. . . .
. CONNECT_IN(RQ) . XID(CMD) . XID . XID
o<---------------o<-----------------------------o<--------------o<-----
| CONNECT_IN(RSP). create . .
*--------------->o-------------->o . .
. | new LDLC . .
. o----------------------------->o .
. | XID(CMD) . . .
. *-------------->o . .
. XID | . .
o<-------------------------------* . .
| XID . XID(RSP) . XID
*------------------------------->o----------------------------->o----->
Figure 4. Regular TG Activation (incoming)
In Figure 4, when an XID is received for a new link, it is passed to
the DLC manager. The DLC manager sends CONNECT_IN(RQ) to notify CS
of the incoming link activation, and CS sends CONNECT_IN(+RSP)
accepting the link activation. The DLC manager then creates a new
instance of LDLC, informs the link demultiplexor, and forwards the
XID to to CS via LDLC. CS then responds by sending an XID to the
adjacent node.
Dudley Informational [Page 17]
RFC 2353 APPN/HPR in IP Networks May 1998
The two following figures show normal TG deactivation (outgoing and
incoming).
*------------------------------------------------------------------*
|CS DLC LDLC DMUX UDP|
*------------------------------------------------------------------*
. . . . .
. DEACT . DISC . DISC
o------------------------------->o----------------------------->o----->
. DEACT . DM . DM . DM
o<-------------------------------o<-------------o<--------------o<-----
| DISCONNECT(RQ) . destroy . . .
*--------------->o-------------->o . .
DISCONNECT(RSP) | . .
o<---------------* . .
Figure 5. Regular TG Deactivation (outgoing)
In Figure 5 upon receiving STOP_LS(RQ) from NOF, CS sends DEACT to
notify the partner node that the HPR link is being deactivated. When
the response is received, CS sends DISCONNECT(RQ) to the DLC manager,
and the DLC manager deactivates the instance of LDLC. Upon receiving
DISCONNECT(RSP), CS sends STOP_LS(RSP) to NOF.
*------------------------------------------------------------------*
|CS DLC LDLC DMUX UDP|
*------------------------------------------------------------------*
. . . . .
. DEACT . DISC . DISC . DISC
o<-------------------------------o<-------------o<--------------o<-----
| . | DM . DM
| . *----------------------------->o----->
| DISCONNECT(RQ) . destroy . . .
*--------------->o-------------->o . .
.DISCONNECT(RSP) | . .
o<---------------* . .
Figure 6. Regular TG Deactivation (incoming)
In Figure 6, when an adjacent node deactivates a TG, the local node
receives a DISC. CS sends STOP_LS(IND) to NOF. Because IP is
connectionless, the DLC manager is not aware that the link has been
deactivated. For that reason, CS also needs to send DISCONNECT(RQ)
to the DLC manager; the DLC manager deactivates the instance of LDLC.
Dudley Informational [Page 18]
RFC 2353 APPN/HPR in IP Networks May 1998
2.5.1.1 Limited Resources and Auto-Activation
To reduce tariff charges, the APPN architecture supports the
definition of switched links as limited resources. A limited-
resource link is deactivated when there are no sessions traversing
the link. Intermediate HPR nodes are not aware of sessions between
logical units (referred to as LU-LU sessions) carried in crossing RTP
connections; in HPR nodes, limited-resource TGs are deactivated when
no traffic is detected for some period of time. Furthermore, APPN
links may be defined as auto-activatable. Auto-activatable links are
activated when a new session has been routed across the link.
An HPR node may have access to an IP network via a switched access
link. In such environments, it may be advisable for customers to
define regular HPR/IP links as limited resources and as being auto-
activatable.
2.5.2 IP Connection Networks
Connection network support for IP networks (option set 2010), is
described in this section.
APPN architecture defines single link TGs across the point-to-point
lines connecting APPN nodes. The natural extension of this model
would be to define a TG between each pair of nodes connected to a
shared access transport facility (SATF) such as a LAN or IP network.
However, the high cost of the system definition of such a mesh of TGs
is prohibitive for a network of more than a few nodes. For that
reason, the APPN connection network model was devised to reduce the
system definition required to establish TGs between APPN nodes.
Other TGs may be defined through the SATF which are not part of the
connection network. Such TGs (referred to as regular TGs in this
document) are required for sessions between control points (referred
to as CP-CP sessions) but may also be used for LU-LU sessions.
In the connection network model, a virtual routing node (VRN) is
defined to represent the SATF. Each node attached to the SATF
defines a single TG to the VRN rather than TGs to all other attached
nodes.
Topology and routing services (TRS) specifies that a session is to be
routed between two nodes across a connection network by including the
connection network TGs between each of those nodes and the VRN in the
Route Selection control vector (RSCV). When a network node has a TG
to a VRN, the network topology information associated with that TG
includes DLC signaling information required to establish connectivity
to that node across the SATF. For an end node, the DLC signaling
Dudley Informational [Page 19]
RFC 2353 APPN/HPR in IP Networks May 1998
information is returned as part of the normal directory services (DS)
process. TRS includes the DLC signaling information for TGs across
connection networks in RSCVs.
CS creates a dynamic link station when the next hop in the RSCV of an
ACTIVATE_ROUTE signal received from session services (SS) is a
connection network TG or when an adjacent node initiates link
activation upon receiving such an ACTIVATE_ROUTE signal. Dynamic
link stations are normally treated as limited resources, which means
they are deactivated when no sessions are using them. CP-CP sessions
are not supported on connections using dynamic link stations because
CP-CP sessions normally need to be kept up continuously.
Establishment of a link across a connection network normally requires
the use of CP-CP sessions to determine the destination IP address.
Because CP-CP sessions must flow across regular TGs, the definition
of a connection network does not eliminate the need to define regular
TGs as well.
Normally, one connection network is defined on a LAN (i.e., one VRN
is defined.) For an environment with several interconnected campus
IP networks, a single wide-area connection network can be defined; in
addition, separate connection networks can be defined between the
nodes connected to each campus IP network.
2.5.2.1 Establishing IP Connection Networks
Once the port is defined, a connection network can be defined on the
port. In order to support multiple TGs from a port to a VRN, the
connection network is defined by the following process:
1. A connection network and its associated VRN are defined on the
port. This is accomplished by the node operator issuing a
DEFINE_CONNECTION_NETWORK(RQ) command to NOF and NOF passing a
DEFINE_CN(RQ) signal to CS.
2. Each TG from the port to the VRN is defined by the node operator
issuing DEFINE_CONNECTION_NETWORK_TG(RQ) to NOF and NOF passing
DEFINE_CN_TG(RQ) to CS.
Prior to implementation of Resource ReSerVation Protocol (RSVP)
support, only one connection network TG between a port and a VRN is
required. In that case, product support for the DEFINE_CN_TG(RQ)
signal is not required because a single set of port configuration
parameters for each connection network is sufficient. If a NOF
implementation does not support DEFINE_CN_TG(RQ), the parameters
listed in the following section for DEFINE_CN_TG(RQ), are provided by
DEFINE_CN(RQ) instead. Furthermore, the Connection Network TG
Dudley Informational [Page 20]
RFC 2353 APPN/HPR in IP Networks May 1998
Numbers (X'81') subfield in the TG Descriptor (X'46') control vector
on an activation XID is only required to support multiple connection
network TGs to a VRN, and its use is optional.
*-----------------------------------------------------*
| NO NOF CS |
*-----------------------------------------------------*
DEFINE_CONNECTION_NETWORK(RQ) DEFINE_CN(RQ) .
o------------------------>o----------------->o
DEFINE_CONNECTION_NETWORK(RSP) DEFINE_CN(RSP) |
o<------------------------o<-----------------*
DEFINE_CONNECTION_NETWORK_TG(RQ) DEFINE_CN_TG(RQ) .
o------------------------>o----------------->o
DEFINE_CONNECTION_NETWORK_TG(RSP) DEFINE_CN_TG(RSP)|
o<------------------------o<-----------------*
Figure 7. IP Connection Network Definition
An incoming dynamic link activation may be rejected with sense data
X'10160046' if there is an existing dynamic link between the two
ports over the same connection network (i.e., with the same VRN CP
name). If a node receives an activation XID for a dynamic link with
an IP address pair, a SAP pair, and a VRN CP name that are the same
as for an active dynamic link, that node can assume that the link has
failed and that the partner node is reactivating the link. In such a
case as an optimization, the node receiving the XID can take down the
active link and allow the link to be reestablished in the IP network.
Because UDP packets can arrive out of order, implementation of this
optimization requires the use of a timer to prevent a stray XID from
deactivating an active link.
Once all the connection networks are defined, the node operator
issues START_PORT(RQ), NOF passes the associated signal to CS, and CS
passes ACTIVATE_PORT(RQ) to the DLC manager. Upon receiving the
ACTIVATE_PORT(RSP) signal from the DLC manager, CS sends a TG_UPDATE
signal to TRS for each defined connection network TG. Each signal
notifies TRS that a TG to the VRN has been activated and includes TG
vectors describing the TG. If the port fails or is deactivated, CS
sends TG_UPDATE indicating the connection network TGs are no longer
operational. Information about TGs between a network node and the
VRN is maintained in the network topology database. Information
about TGs between an end node and the VRN is maintained only in the
local topology database. If TRS has no node entry in its topology
database for the VRN, TRS dynamically creates such an entry. A VRN
node entry will become part of the network topology database only if
Dudley Informational [Page 21]
RFC 2353 APPN/HPR in IP Networks May 1998
⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -