📄 rfc1434.txt
字号:
| Message Length ----> . | | Remote Data Link Correlator ----> . | | . . | | Remote DLC Port ID ----> . | | . . | | Reserved Field ----> . | | Message Type Reserved Field | | Protocol ID Header Number | | Header Length ----> . | | Reserved Field ----> . | | Reserved Field Message Type | | Target MAC Address ----> . | | . . | | . . | | Origin MAC Address ----> . | | . . | | . . | | Origin Link SAP Target Link SAP | | Frame Direction Reserved Field | | Message Length ----> . | | DLC Header Length ----> . | | Origin DLC Port ID ----> . | | . . | | Origin Data Link Correlator ----> . | | . . | | Origin Transport ID ----> . | | . . | | Target DLC Port ID ----> . | | . . | | Target Data Link Correlator ----> . | | . . | | Target Transport ID ----> . | | . . | | Reserved Field ----> . | | . . | +-----------------------------------------------------------------+ (Even Byte) (Odd Byte)Dixon & Kushi [Page 6] RFC 1434 DLS: Switch-to-Switch Protocol March 1993 INFORMATION MESSAGE (16 Bytes) +-----------------------------------------------------------------+ | Version Reserved Field | | Message Length ----> . | | Remote Data Link Correlator ----> . | | . . | | Remote DLC Port ID ----> . | | . . | | Reserved Field ----> . | | Message Type Reserved Field | +-----------------------------------------------------------------+ (Even Byte) (Odd Byte) The Version Number is set to x'4B', indicating a numeric value of 75. The Header Length is x'00 48', indicating a numeric value of 72 bytes. The Header Number is x'01', indicating a value of one. The Frame Direction field is set to x'01' for frames sent from the origin DLS to the target DLS, and is set to x'02' for frames sent from the target DLS to the origin DLS. Note: The Remote Data Link Correlator and Remote DLC Port ID are set equal to the Target Data Link Correlator and Target DLC Port ID if the Frame Direction field is set to x'01', and are set equal to the Origin Data Link Correlator and Origin DLC Port ID if the Direction Field is set to x'02'. The Protocol ID field is set to x'42', indicating a numeric value of 66. The Message Length field defines the number of bytes within the data field following the header. Note that this value is specified in two different fields of the message header. The DLC Header Length is set to zero for SNA and is set to x'23' for NetBIOS datagrams, indicating a length of 35 bytes. This includes the Access Control (AC) field, the Frame Control (FC) field, Destination MAC Address (DA), the Source MAC Address (SA), the Routing Information (RI) field (padded to 18 bytes), the Destination link SAP (DSAP), the Source link SAP (SSAP), and the LLC control field (UI). The values for the Message Type field are defined in a later section. Note that this value is specified in two different fields of the message header.Dixon & Kushi [Page 7] RFC 1434 DLS: Switch-to-Switch Protocol March 1993 Reserved fields are set to zero upon transmission and should be ignored upon receipt.3.2. Address Parameters A data link is defined as a logical association between the two end stations using Data Link Switching. It is identified by a Data Link ID (14 bytes) consisting of the pair of attachment addresses associated with each end system. Each attachment address is represented by the concatenation of the MAC address (6 bytes) and the LLC address (1 byte). DATA LINK ID (14 Bytes) +-----------------------------------------------------------------+ |Target MAC Address ----> . | | . . | | . . | |Origin MAC Address ----> . | | . . | | . . | |Origin Link SAP Target Link SAP | +-----------------------------------------------------------------+ An end-to-end circuit is identified by a pair of Circuit ID's. A Circuit ID is a 64 bit number that identifies the DLC circuit within a single DLS. It consists of a DLC Port ID (4 bytes), and a Data Link Correlator (4 bytes). This value is unique in a single DLS and is assigned locally. The pair of Circuit ID's along with the identifiers of the Data Link Switches, uniquely identify a single end-to-end circuit. Each DLS must keep a table of these Circuit ID pairs, one for the local end of the circuit and the other for the remote end of the circuit. In order to identify which Data Link Switch originated the establishment of a circuit, the terms, origin DLS and target DLS, will be employed in this document. CIRCUIT ID (8 Bytes) +-----------------------------------------------------------------+ |DLC Port ID ----> . | | . . | |Data Link Correlator ----> . | | . . | +-----------------------------------------------------------------+ The Origin Transport ID and the Target Transport ID fields in the message header are used to identify the individual TCP/IP port on a Data Link Switch. The values have only local significance. However, each Data Link Switch is required to reflect the values contained in these two fields, along with the associated values for DLC Port IDDixon & Kushi [Page 8] RFC 1434 DLS: Switch-to-Switch Protocol March 1993 and the Data Link Correlator, when returning a message to the other Data Link Switch. The following figure shows the use of the addressing parameters during the establishment of an end-to-end connection. The CANUREACH, ICANREACH, and REACH_ACK messages all carry the Data Link ID, consisting of the MAC and Link SAP addresses associated with the two end stations. Upon receipt of a CANUREACH message, the target DLS starts a data link for each port, thereby obtaining a Data Link Correlator. If the target station can be reached, an ICANREACH message is returned to the origin DLS containing the Target Circuit ID parameter. Upon receipt, the origin DLS starts a data link and returns the Origin Circuit ID to the target DLS within the REACH_ACK message. If the REACH_ACK message is not successfully received, the target Data Link Switch can obtain the Origin Circuit ID from a subsequent message (i.e., CONTACT, XIDFRAME, or DGRMFRAME). +------------+ +------------+ |Disconnected| |Disconnected| +------------+ CANUREACH (Data Link ID) +------------+ -------------------------------------------------> ICANREACH (Data Link ID, Target Circuit ID) <------------------------------------------------ REACH_ACK (Data Link ID, Origin Cir ID, Target Cir ID) -------------------------------------------------> +------------+ +------------+ |Circuit Est.| |Circuit Est.| +------------+ +------------+ XIDFRAME (Data Link ID, Origin Cir ID, Target Cir ID) <------------------------------------------------> CONTACT (Data Link ID, Origin Cir ID, Target Cir ID) -------------------------------------------------> CONTACTED (Data Link ID, Origin Cir ID, Target Cir ID) <------------------------------------------------- +------------+ +------------+ | Connected | | Connected | +------------+ +------------+ INFOFRAME (Remote Circuit ID = Target Circuit ID) -------------------------------------------------> INFOFRAME (Remote Circuit ID = Origin Circuit ID) <------------------------------------------------- Figure 3. DLS Circuits and Connections During the exchange of the XIDFRAME, CONTACT, and CONTACTED messages, the pair of Circuit ID parameters is included in the message format along with the DATA LINK ID parameter. Once the connection has been established, the INFOFRAME messages are exchanged with the shorterDixon & Kushi [Page 9] RFC 1434 DLS: Switch-to-Switch Protocol March 1993 header. This header contains only the Circuit ID associated with the remote DLS. The Remote Data Link Correlator and the Remote DLC Port ID are set equal to the Data Link Correlator and the DLC Port ID that are associated with the origin or target Data Link Switch, dependent upon the direction of the packet.3.3. Message Types The following table lists the protocol data units that are exchanged between Data Link Switches. All values not listed are reserved for potential use in follow-on releases. Command Function Hex Value ------- -------- --------- CANUREACH Can U Reach Station x'03' ICANREACH I Can Reach Station x'04' REACH_ACK Reach Acknowledgment x'05' DGRMFRAME Datagram Frame (See note) x'06' XIDFRAME XID Frame x'07' CONTACT Contact Remote Station x'08' CONTACTED Remote Station Contacted x'09' RESTART_DL Restart Data Link x'10' DL_RESTARTED Data Link Restarted x'11' INFOFRAME Information (I) Frame x'0A' HALT_DL Halt Data Link x'0E' DL_HALTED Data Link Halted x'0F' NETBIOS_NQ NetBIOS Name Query x'12' NETBIOS_NR NetBIOS Name Recognized x'13' DATAFRAME Data Frame (See note) x'14' NETBIOS_ANQ NetBIOS Add Name Query x'1A' NETBIOS_ANR NetBIOS Add Name Response x'1B' Table 1. SSP Message Types Note: Both the DGRMFRAME and DATAFRAME messages are used to carry information received by the DLC entity within UI frames. As will be explained below, the DGRMFRAME message is addressed according to a pair of Circuit IDs, while the DATAFRAME message is addressed according to a Data Link ID, being composed of a pair of MAC addresses and a pair of link SAP addresses. The latter is employed prior to the establishment of an end-to-end circuit when Circuit IDs have yet to be established. For the exchange of NetBIOS control messages, the entire DLC header is carried as part of the message unit. This includes the MAC header, with the routing information field padded to 18 bytes, and the LLC header. The following message types are affected: NETBIOS_NQ, NETBIOS_NR, NETBIOS_ANQ, NETBIOS_ANR, and DATAFRAME whenDixon & Kushi [Page 10] RFC 1434 DLS: Switch-to-Switch Protocol March 1993 being used by NetBIOS systems. The routing information in the DLC header is not used by the remote Data Link Switch upon receiving the above five messages.4. Protocol Specification This section provides a description of the Switch-to-Switch Protocols. Included is a set of high-level protocol flows and a detail set of state transition tables. The states and the protocols are described in terms that are intended to be generic to different platforms. Emphasis of the technical details is to ensure operability of the IBM 6611 with another vendor's implementation.⌨️ 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 + -