DCAP, Data Link Switching Client Access Protocol

Description Glossary RFCs Publications Obsolete RFCs


Protocol suite: TCP/IP.
Protocol type:Application layer protocol.
Multicast addresses: (server). (client). (group).
Ports:1973 (TCP) server.
Working groups:

DCAP is used between workstations and routers to transport SNA/ NetBIOS traffic.

MAC header IP header TCP header DCAP header Data :::

DCAP header:

0001020304050607 0809101112131415 1617181920212223 2425262728293031
Protocol Version Type Length
Data :::

Protocol. 4 bits.
Set to 8.

Version. 4 bits.
Set to 1.

Type. 8 bits.
DCAP message.

1CAN_U_REACH.Find if the station given is reachable.
2I_CAN_REACH.Positive response to CAN_U_REACH.
3I_CANNOT_REACH.Negative response to CAN_U_REACH.
4START_DL.Setup session for given addresses.
5DL_STARTED.Session Started.
6 START_DL_FAILED. Session Start failed.
8 CONTACT_STN. Contact destination to establish SABME.
9 STN_CONTACTED. Station contacted - SABME mode set.
10 DATA_FRAME. Connectionless Data Frame for a link.
11 INFO_FRAME. Connection oriented I-Frame.
12 HALT_DL. Halt Data Link session.
13 HALT_DL_NOACK. Halt Data Link session without ack.
14 DL_HALTED. Session Halted.
15 FCM_FRAME. Data Link Session Flow Control Message.
17 DGRM_FRAME. Connectionless Datagram Frame for a circuit.
18 CAP_XCHANGE. Capabilities Exchange Message.
19 CLOSE_PEER_REQUEST. Disconnect Peer Connection Request.
20 CLOSE_PEER_RESPONSE. Disconnect Peer Connection Response.
29PEER_TEST_REQ.Peer keepalive test request.
30PEER_TEST_RSP.Peer keepalive response.

Length. 16 bits.
Size of the packet including the DCAP header, DCAP data and user data. The minimum size of the packet is 4 bytes.

Data. Variable length.



[RFC 2114] Data Link Switching Client Access Protocol.


Obsolete RFCs:

[RFC 2106] Data Link Switching Remote Access Protocol.

Description Glossary RFCs Publications Obsolete RFCs