Internet Draft Danny Cohen
Myricom
Expires in six months Craig Lund
Mercury Computers
Tony Skjellum, Thom McMahon, Robert George
Mississippi State University
June 1998
The Router-to-Router (RRP) PacketWay Protocol for
High-Performance Interconnection of Computer Clusters
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
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Table of Contents
Introduction ..................................................... 2
Notations ........................................................ 2
PacketWay and IP ................................................. 3
Node Attributes .................................................. 3
RRP Messages ..................................................... 4
Structure of RRP Messages ........................................ 5
RRP Records ...................................................... 8
Example .......................................................... 12
Glossary ......................................................... 16
Acronyms and Abbreviations ....................................... 18
Editor's Address ................................................. 19
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Introduction
The PacketWay family of protocols is introduced in the "The End-to-
End (EEP) PacketWay Protocol for High-Performance Interconnection of
Computer Clusters". This document defines the Router-to-Router
Protocol (RRP), the basic messages used by routers to exchange
routing information with endpoints and each other.
In the PacketWay model a router is a set of cooperating hosts on two
(or more) networks. These hosts, each a full-fledged host on its
SAN, are called "half-routers" (HRs). RRP defines, via message
structure and behavior, the interactions between HRs as well as the
interactions between HRs and nodes.
RRP does not define the lower level protocols that deliver its
messages. RRP also does not define the connection between the HRs
within the router-- these are left for mutual agreements among the
implementors of each HR.
However, the intra-router communication among these hosts is a
"public" issue, handled according to the RRP which defines only the
Network-level [Level-3], and not the lower levels of this
communication. All RRP messages are carried via EEP packets with the
"Packet-Type" field of the EEP header set to "RRP".
This document does not define how source routes are initially
constructed. It is expected that static tables may be manually
maintained for simple or very stable systems. Dynamic table-
maintenance protocols will likely be outlined in a future document.
Notations
8B means "8-byte" (64 bits).
0x indicates hexadecimal values, e.g., 0x0100 is
2^8=256(decimal).
0b indicates binary values, e.g., 0b0100 is 4(decimal).
xxxx indicate a field that is discarded without any checking (e.g.,
padding).
[exp] in equations, is the integral part, rounded down, of `exp`
(e.g., [23/8]=2).
All length fields do not include themselves, and therefore may be 0.
Lengths are specified either (a) by byte count, implying that some
padding bytes may follow to fill 8B-words, or (b) by 8B-word count
and PL, the number of trailing padding bytes (with PL between 0 and
7).
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PacketWay and IP
The architecture of PacketWay is very similar to the IP family (in
fact it heavily borrows from IP), with emphasis on performance not
generality and scaleability as was selected for IP.
Like IP, PacketWay is based on an End-to-End protocol (EEP) that
assumes that if an address (or equivalent specification of the desti-
nation) is placed in the appropriate field in the packet header, then
the packet will arrive to that destination. Neither IP nor EEP
specify how this happens.
Routers are responsible for transferring packets from their source
networks to their destination networks (possibly via other networks).
The communication among the routers (such the entire family of the
GGPs [Gateway/Gateway Protocols] as they were originally called) is
NOT a part of IP (as defined originally in RFC-791 and MIL-STD-1777).
Similarly, it is not a part of EEP.
Like the IP family, PacketWay defines separately its Router-to-Router
Protocol (RRP), in a device- and network-independent manner.
However, the model of routers in PacketWay is slightly different from
the original model in the IP family. IP routers (or gateways as they
were called then) are monolithic devices, provided by their vendors.
Each IP-router is a bona-fide host on two (or more) networks. The
communication among these intra-router hosts is an internal "private"
issue, handled by each vendor as it sees fit, not subject to pub-
lished standards.
Node Attributes
Each node must have a Physical Address. Optionally it may also have
Name, Capabilities, and Logical-Addresses:
Physical Address 23 bits, flat, unique in this PacketWay.
Name flat, globally unique (e.g., IP address), arbi-
trary length
Capabilities regular GP node, router, PacketWay-server, NFS,
paging server, M/C server, SRVLOC-server, DSP,
printer, etc.
Some capabilities may need additional parameters
(e.g., SAN-ID for routers, and resolution+colors
for printers). Their parameters are capability-
specific. The capabilities are defined in the
PacketWay Enumeration document.
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Logical-Addresses a set of (logical) addresses to which this node
requests to listen. Logical addresses designate
multicast and broadcast groups.
The control of the Logical-Addresses (a la IGMP)
is not defined in this document. This will be
designed by the applications that use it (e.g.,
PacketWay-Multicast).
The management of logical addresses (e.g., JOIN
and LEAVE) is not defined here.
RRP Messages
RRP messages are PacketWay messages with PT="RRP" and TE="RRP-Type"
in their EEP-header, followed by zero or more RRP-records according
to their RRP-type and completed by the TAIL which is the EI field of
the EEP packet. The RRP-records are defined in the next sections.
The RRP-records constitute the Data Block (DB) of the PacketWay-
message. They must be in Big-Endian order, with e=0 in the EEP-
header.
We use "[XXX]" to indicate the RRP-message XXX, and <YYY> to indicate
the RRP-record YYY. XXX is the RRP-Type, carried in the Type
Extension (TE) field of the EEP header (with Packet-Type of "RRP"),
and YYY is the RTyp field, carried in the first byte of that
RRP-record.
Following are the 7 RRP messages, with their RRP-type, and the
related error messages. The column S->D (Source to Destination)
shows who sends such messages to whom, where N is for Node, H is for
HR, and A is for Any.
RRP-
Type S->D Description
-------- ------ -----------------------------------------------
[GVL2] N->H Please give me L2-routes to node (address)
Replies to [GVL2]: [L2SR], [RDRC], or [ERR/UNK].
[L2SR] H->N Here are L2-routes to node (address)
[HRTO] N->H Which HR should I use for node (address)?
Replies to [HRTO]: [RDRC] or [ERR/UNK].
[RDRC] H->N Re-direct to node (address) via an HR on same SAN
[TELL] N->H Please tell me about node (address, name, capa's)
The reply to [TELL] is [INFO], or [ERR/UNK].
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[INFO] A->A Info about node (address, name, capabilities, LAs)
[WRU?] A->A Who/what-Are-You? (Tell me all about yourself)
The reply to [WRU?] is [INFO] about the replier.
RRP also uses the following error messages:
[ERR/UNK] Destination Unknown (address)
[ERR/HRDOWN] HR Down
[ERR/LKDOWN] Link Down
[ERR/GENERAL] General error message
[GVL2] Please give me L2-routes from you to node (address)
PH (with [PT/TE]=[RRP/GVL2])
<ADDR> (address of the node for which [L2SR] is
requested)
Structure of RRP Messages
[L2SR] Here are L2-routes from me to node (address)
PH (with [PT/TE]=[RRP/L2SR])
<ADDR> (address of the node for which the following
<SRQR> is provided)
<SRQR> (Source Route/Quality record)
<MTUR> (optional) MTU records for the above <SRQR>
This message may have several (<SRQR>, <MTUR>) pairs,
one such pair for each source route.
[HRTO] Which HR should I use for node (address)
PH (with [PT/TE]=[RRP/HRTO])
<ADDR> (address of the node for which initial HR
is requested)
[RDRC] Re-direct to destination node (address) via a HR
(address), on the same SAN.
PH (with [PT/TE]=[RRP/RDRC])
<ADDR> (address of the destination node)
<ADDR> (address of the HR to be used for that
destination)
The above addresses are expected to be physical
(but they be otherwise).
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[TELL] Please tell me about node
(address | name | capabilities)
PH (with [PT/TE]=[RRP/TELL])
<ADDR> (address of that node)
or
PH (with [PT/TE]=[RRP/TELL])
<NAME> (name of that node)
or
PH (with [PT/TE]=[RRP/TELL])
<CAPA> (capabilities for which nodes are requested)
This message may have several <CAPA>'s, one for each
capability.
[TELL] identifies a node by an address and/or a name
and/or capabilities. If more than one attribute is
specified (e.g., an address and name(s)) any nodes
that meets any of them should be considered (like an
implied OR).
[INFO] Info about node(s) (address, name, capabilities)
PH (with [PT/TE]=[RRP/INFO])
<ADDR> (address of that node)
<NAME> (name of that node)
<CAPA> (capabilities for which nodes are requested)
<LADR> (Logical-Addresses for the requested node)
This message may have several <CAPA>'s, one for each
capability. For nodes without <NAME>, <LADR>, or any
<CAPA>, these records are omitted.
[INFO] provides all the known information about all
the nodes that match the [TELL]. The <ADDR>-records
are the separators between the nodes.
[WRU?] Who/what-Are-You?
PH (with [PT/TE]=[RRP/WRU?] and [DD]=0x7FFFFE)
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[ERR/UNK] Destination Unknown (address)
PH (with [PT/TE]=ERROR/UNK)
<XXXX> (XXXX of the Destination node for which the
requested information is not available),
where >XXXX> is the <ADDR> and/or <NAME>
<and/or CAPA> of the node(s) about which
this message is sent
[ERR/HRDOWN] HR Down (or Router-Down)
PH (with [PT/TE]=[ERROR/HRDOWN])
<ADDR> (address of the HR that is down)
<ADDR> (the other address of the router that is down)
[ERR/LINKDOWN] Link Down
PH (with [PT/TE]=[ERROR/LINKDOWN])
<ADDR> (address of one end of the link that is down)
<ADDR> (address of the other end of the link that is
down)
[ERR/GENERAL] General Error (i.e., none of the above)
PH (with [PT/TE]=[ERROR/GENERAL])
XX (The entire message that caused the error :
PH+OH+DB+TAIL)
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RRP Records
Each RRP-record starts with an 8B-word header as shown below. Its
first byte identifies the record type (RTyp). The second byte is the
Pad-Count byte (PL) indicating the number of padding bytes. The
third and the fourth bytes (RL) are the length (in 8B-words) of the
record, excluding the record header, hence it may be zero. The rest
of the header bytes depend on the record type (RTyp).
+--------+--------+--------+--------+--------+--------+--------+--------+
| RTyp | PL | RL |........|........|........|........|
+--------+--------+--------+--------+--------+--------+--------+--------+
Some records that have an arbitrary length are "right justified" by
having PL padding bytes before the data (Padding Before Data [PBD]).
Some records that have an arbitrary length are "left justified" by
having PL bytes after the data (Padding After Data [PAD]). In either
case the total number of data bytes is: (8*RL+4-PL).
Following are the RRP-records. These records are the building blocks
used to construct RRP-messages. In the following, "xxxx" indicate
bytes that are discarded, such as for padding. It is recommended to
set them to all-0.
===> <ADDR> Node-Address Record [PAD]
This record specifies either a single address (with AT=1) or a range
of addresses (with AT=2 followed by AT=3, or by AT=4 followed by
AT=5). AT is the "Address-Type".
0 1 2 3 4 5 6 7
+--------+--------+--------+--------+--------+--------+--------+--------+
| <ADDR> | PL=0 | RL=0 | AT=1 | PacketWay-Address |
+--------+--------+--------+--------+--------+--------+--------+--------+
or:
0 1 2 3 4 5 6 7
+--------+--------+--------+--------+--------+--------+--------+--------+
| <ADDR> | PL=4 | RL=1 | AT=2 | Min-PacketWay-Address |
+--------+--------+--------+--------+--------+--------+--------+--------+
| AT=3 | Max-PacketWay-Address | xxxx | xxxx | xxxx | xxxx |
+--------+--------+--------+--------+--------+--------+--------+--------+
or:
0 1 2 3 4 5 6 7
+--------+--------+--------+--------+--------+--------+--------+--------+
| <ADDR> | PL=4 | RL=1 | AT=4 | PacketWay-Address-Value |
+--------+--------+--------+--------+--------+--------+--------+--------+
| AT=5 | PacketWay-Address-Mask | xxxx | xxxx | xxxx | xxxx |
+--------+--------+--------+--------+--------+--------+--------+--------+
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The address-mask follows the address-value.
The above addresses may be physical or logical.
The address X is specified by an <ADDR>-record if:
if AT=1: X == PacketWay-Address
if AT=2,3: Min-PacketWay-Address <= X <= Max-PacketWay-Address
if AT=4,5: (PacketWay-Address-Mask & X) == PacketWay-Address-Value
An <ADDR>-record defines only one PacketWay-address (or one range),
unlike an <LADR>-record (see below) that may specify multiple addresses
and multiple address-ranges.
If the <ADDR>-record is followed by other records that describe the
same node (such as <NAME>, <CAPA>, <LADR>, <SRQR>, and <MTUR>) then
the RL of the <ADDR>-records also covers all these records. All
these records apply to all the addresses specified in this
<ADDR>-record. Needless to say that <NAME> is not expected to appear
within a record that specifies more than one address.
Hence, if an <ADDR>-record with AT=1 has RL>1, or if an <ADDR>-record
with AT>1 has RL>2, then this <ADDR>-record includes additional records
(such as <CAPA>, <LADR>, <SRQR>, and/or <MTUR>) about the specified
address(es).
The enumeration is guaranteed not to have overlap between the AT and
the RTyp codes.
===> <NAME> Node-Name Record [PAD]
(e.g., a name with 7 bytes B1..B7)
0 1 2 3 4 5 6 7
+--------+--------+--------+--------+--------+--------+--------+--------+
| <NAME> | PL=3 | RL=1 | B1 | B2 | B3 | B4 |
+--------+--------+--------+--------+--------+--------+--------+--------+
| B5 | B6 | B7 | xxxx | xxxx | xxxx | xxxx | xxxx |
+--------+--------+--------+--------+--------+--------+--------+--------+
The number of bytes in the name is 8*RL+4-PL.
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===> <CAPA> Node-Capability Record [PAD]
(e.g., 9 parameter bytes)
0 1 2 3 4 5 6 7
+--------+--------+--------+--------+--------+--------+--------+--------+
| <CAPA> | PL=2 | RL=1 | CC=Cx | P1 | P2 | P3 |
+--------+--------+--------+--------+--------+--------+--------+--------+
| P4 | P5 | P6 | P7 | P8 | P9 | xxxx | xxxx |
+--------+--------+--------+--------+--------+--------+--------+--------+
Byte#4 is the Capability Code, CC, followed by as many parameter
bytes as needed (9 in the above example).
The capability codes are listed in the PacketWay Enumeration docu-
ment.
The number of bytes used by the parameters is 8*RL+3-PL.
===> <LADR> Logical-Addresses Record [PAD]
(e.g., 2 logical addresses and a range of logical addresses)
0 1 2 3 4 5 6 7
+--------+--------+--------+--------+--------+--------+--------+--------+
| <LADR> | PL=4 | RL=2 | AT=1 |1110 Logical-Address-#1 |
+--------+--------+--------+--------+--------+--------+--------+--------+
| AT=2 |1110 Min-Logical-Address | AT=3 |1110 Max-Logical-Address |
+--------+--------+--------+--------+--------+--------+--------+--------+
| AT=1 |1110 Logical-Address-#2 | xxxx | xxxx | xxxx | xxxx |
+--------+--------+--------+--------+--------+--------+--------+--------+
Whereas an <ADDR>-record defines only one PacketWay-address (or one
range), an <LADR>-record may specify multiple addresses (each with
AT=1) and multiple ranges (each with a pair of AT=2,3 or AT=4,5).
===> <SRQR> Source-Route Record [PBD], with Q for that route.
(e.g., an SR combined of 2 L2RHs, one with 13 bytes and one with 4
bytes)
This record carries one, or more, L2RHs (2 in the following example,
one with SR of 13B, followed by an SR of 5B).
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0 1 2 3 4 5 6 7
+--------+--------+--------+--------+--------+--------+--------+--------+
| <SRQR> | PL=2 | RL=3 | xxxx | xxxx | Q |
+--------+--------+--------+--------+--------+--------+--------+--------+
|vv000000|10 L=13B| SR01 | SR02 | SR03 | SR04 | SR05 | SR06 |
+--------+--------+--------+--------+--------+--------+--------+--------+
| SR07 | SR08 | SR09 | SR10 | SR11 | SR12 | SR13 | xxxx |
+--------+--------+--------+--------+--------+--------+--------+--------+
|vv000000|10 L=4B | SR01 | SR02 | SR03 | SR04 | xxxx | xxxx |
+--------+--------+--------+--------+--------+--------+--------+--------+
Q (the Route Quality) is an unsigned 16-bit integer. The units are
not defined here. It is assumed that it is monotonic with all-0
being the best and all-1 the worst. If there is an <MTUR>
(MTU-record) for that SR it should follow this <SRQR>-record.
However, the RL of the <SRQR> does not include the RL of the <MTUR>.
===> <MTUR> MTU record [PBD]
0 1 2 3 4 5 6 7
+--------+--------+--------+--------+--------+--------+--------+--------+
| <MTUR> | PL=0 | RL=0 | MTU (in 8B-words) |
+--------+--------+--------+--------+--------+--------+--------+--------+
The MTU record provides the MTU for the SR defined before (by an
<SRQR>).
The value of 0 means indefinite MTU (i.e., any length is OK).
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Example
In the following PacketWay network used for this example, 3 SANs are
interconnected via 2 routers, Router-A (RTRA) between SAN1 and SAN3,
and RTRB between SAN1 and SAN2.
+-------+ +--0--+ SAN1 +--0--+ +--0--+
| Node1 +----------3 SW0 1----------3 SW1 1----------3 SW2 1 MTU=16KB
+-------+ +--2--+ +--2--+ +--2--+
| |
RTRA1 *********** +---+---+ *********** RTRB1
* RouterA * | Node2 | * RouterB *
RTRA3 *********** +---+---+ *********** RTRB2
| | |
+-------+ SAN3 +--0--+ +--0--+ SAN2 +--0--+
| Node3 +----------3 SW3 1 3 SW4 1----------3 SW5 1 MTU=8KB
+-------+ +--2--+ +--2--+ +--2--+
In this example Node1 on SAN1 (with MTU=16KB) is looking for Node2
which is on SAN2 (with MTU=8KB). It first asks its default router
(RTRA1) for an L2RH to Node2. RTRA1 redirects Node1 to RTRB1
regarding Node2.
Node1 asks RTRA1 (by [HRTO], in message M1) which router to use for
Node2. RTRA1 suggests (using [RDRC], M2) to use RouterB. Node1 uses
L3-forwarding ([WRU?], M3), via Router-B, to verify that RTRB can
indeed get to Node2, by asking Node2 for information about itself.
Node2 provides this information ([TELL], M4) which Node1 likes.
Node1 asks RouterB ([GVL2], M5) for L2RH(s) to Node2. RouterB pro-
vides ([L2SR], M6) the requested L2RH with its MTU of 1,024 8B-words
(8KB).
Finally, Node1 sends data (by M7) to Node2 using L2-forwarding.
Similarly, Node2 may ask its default router which HR to use for Node1
and for L2RH(s) to Node1.
The sequence of messages (M1 thru M7) is shown below.
(M1) Node1 sends [HRTO] to its default router RTRA1 asking which HR
to use for node2.
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0 1 2 3 4 5 6 7
+-----------------------------------------------------------------------+
| <---- The L2-header needed to get from Node1 to RouterA1 ----> |
| It may be any number of bytes. In this example it's 9 bytes:230000000|
+--------+--------+--------+--------+--------+--------+--------+--------+
|00 P |0 RTRA1 | "HRTO" | "R R P" |
+---+----+--------+--------+--------+-+------+--------+--------+--------+
|E=0|PL=0| Data-Length=1 (8B-words) |0| RZ |0 Node1 |
+---+----+--------+--------+--------+-+------+--------+--------+--------+
| <ADDR> | PL=0 | RL=0 | AT=1 |0 Node2 |
+--------+--------+--------+--------+--------+--------+--------+--------+
| 64 zero bits, unless any error was indicated along the path |
+--------+--------+--------+--------+--------+--------+--------+--------+
(M2) RTRA1 uses [RDRC] to re-direct to Node2 via RouterB.
0 1 2 3 4 5 6 7
+-----------------------------------------------------------------------+
| <---- The L2-header needed to get from RouterA1 to Node1 ----> |
| It may be any number of bytes. In this example it's 9 bytes:330000000|
+--------+--------+--------+--------+--------+--------+--------+--------+
|00 P |0 Node1 | "RDRC" | "R R P" |
+---+----+--------+--------+--------+-+------+--------+--------+--------+
|E=0|PL=0| Data-Length=2 (8B-words) |0| RZ |0 RTRA1 |
+---+----+--------+--------+--------+-+------+--------+--------+--------+
| <ADDR> | PL=0 | RL=0 | AT=1 |0 Node2 |
+--------+--------+--------+--------+--------+--------+--------+--------+
| <ADDR> | PL=0 | RL=0 | AT=1 |0 RTRB1 |
+--------+--------+--------+--------+--------+--------+--------+--------+
| 64 zero bits, unless any error was indicated along the path |
+--------+--------+--------+--------+--------+--------+--------+--------+
Node1 knows how to get to RouterB over its SAN.
(M3) Node1 uses [WRU?] (still using L3-forwarding via RouterB) to
verify the capabilities of Node-2, and that RTRB can indeed get to
it. This is done by asking Node2 for information about itself.
0 1 2 3 4 5 6 7
+-----------------------------------------------------------------------+
| <---- The L2-header needed to get from Node1 to RouterB1 ----> |
| It may be any number of bytes. Here it is 11 bytes: 11230000000 |
+--------+--------+--------+--------+--------+--------+--------+--------+
|00 P |0 Node2 | "WRU?" | "R R P" |
+---+----+--------+--------+--------+-+------+--------+--------+--------+
|E=0|PL=0| Data-Length=0 (8B-words) |0| RZ |0 Node1 |
+---+----+--------+--------+--------+-+------+--------+--------+--------+
| 64 zero bits, unless any error was indicated along the path |
+--------+--------+--------+--------+--------+--------+--------+--------+
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(M4) Node2 uses [INFO] (via RouterB2, also using L3-forwarding) to
provide information about itself to Node1. This info includes its
PacketWay-address and its name ("Super"). If Node2 had implemented
also Level-C of the RRP it would also provide a record about its
capabilities (as shown in this example with 2 capabilities (with
codes of 5 and 7).
0 1 2 3 4 5 6 7
+-----------------------------------------------------------------------+
| <---- The L2-header needed to get from Node2 to RouterB2 ----> |
| It may be any number of bytes. Here it is 10 bytes: 1030000000 |
+--------+--------+--------+--------+--------+--------+--------+--------+
|00 P |0 Node1 | "INFO" | "R R P" |
+---+----+--------+--------+--------+-+------+--------+--------+--------+
|E=0|PL=0| Data-Length=5 (8B-words) |0| RZ |0 Node2 |
+---+----+--------+--------+--------+-+------+--------+--------+--------+
| <ADDR> | PL=0 | RL=4 | AT=1 |0 Node2 |
+--------+--------+--------+--------+--------+--------+--------+--------+
| <NAME> | PL=7 | RL=1 | "S" | "u" | "p" | "e" |
+--------+--------+--------+--------+--------+--------+--------+--------+
| "r" | xxxx | xxxx | xxxx | xxxx | xxxx | xxxx | xxxx |
+--------+--------+--------+--------+--------+--------+--------+--------+
| <CAPA> | PL=1 | RL=0 | CC=7 | 4 | 8 | xxxx |
+--------+--------+--------+--------+--------+--------+--------+--------+
| <CAPA> | PL=3 | RL=0 | CC=5 | xxxx | xxxx | xxxx |
+--------+--------+--------+--------+--------+--------+--------+--------+
| 64 zero bits, unless any error was indicated along the path |
+--------+--------+--------+--------+--------+--------+--------+--------+
By receiving this message Node1 knows that RTRB could indeed be used
for communication with Node2.
(M5) Node1 uses [GVL2] to ask RouterB for L2RH(s) from RouterB to
Node2.
0 1 2 3 4 5 6 7
+-----------------------------------------------------------------------+
| <---- The L2-header needed to get from Node1 to RouterB1 ----> |
| It may be any number of bytes. Here it is 11 bytes: 11230000000 |
+--------+--------+--------+--------+--------+--------+--------+--------+
|00 P |0 RTRB1 | "GVL2" | "R R P" |
+---+----+--------+--------+--------+-+------+--------+--------+--------+
|E=0|PL=0| Data-Length=1 (8B-words) |0| RZ |0 Node1 |
+---+----+--------+--------+--------+-+------+--------+--------+--------+
| <ADDR> | PL=0 | RL=0 | AT=1 |0 Node2 |
+--------+--------+--------+--------+--------+--------+--------+--------+
| 64 zero bits, unless any error was indicated along the path |
+--------+--------+--------+--------+--------+--------+--------+--------+
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(M6) RouterB uses [L2SR] to provide Node1 with an L2RH from RTRB2 to
Node2, with its Q and MTU. This L2RH is {3,0,3,0,0,0,0,0,0,0} from
RouterB to Node2, and the MTU is 1,024 (meaning 8KB).
0 1 2 3 4 5 6 7
+-----------------------------------------------------------------------+
| <---- The L2-header needed to get from RouterB1 to Node1 ----> |
| It may be any number of bytes. Here it is 11 bytes: 33330000000 |
+--------+--------+--------+--------+--------+--------+--------+--------+
|00 P |0 Node1 | "L2SR" | "R R P" |
+---+----+--------+--------+--------+-+------+--------+--------+--------+
|E=0|PL=0| Data-Length=4 (8B-words) |0| RZ |0 RTRA1 |
+---+----+--------+--------+--------+-+------+--------+--------+--------+
| <ADDR> | PL=0 | RL=3 | AT=1 |0 Node2 |
+--------+--------+--------+--------+--------+--------+--------+--------+
| <SRQR> | PL=2 | RL=1 | xxxx | xxxx | Q |
+--------+--------+--------+--------+--------+--------+--------+--------+
|vv000000|10 L=4B | 3 | 0 | 3 | 0 | xxxx | xxxx |
+--------+--------+--------+--------+--------+--------+--------+--------+
| <MTUR> | PL=1 | RL=0 | MTU=1,024 (in 8B-words) |
+--------+--------+--------+--------+--------+--------+--------+--------+
| 64 zero bits, unless any error was indicated along the path |
+--------+--------+--------+--------+--------+--------+--------+--------+
The MTU in the <MTUR> above is the lessor of the MTUs of both
networks.
The RL (record-length) of the last <MTUR>-record is NOT included in
the RL of the preceding <SRQR>-record, but is included in the RL of
the preceding <ADDR>-record (since the RL of the <SRQR> is included
in the RL of the <ADDR>). The RL=3 of the <ADDR> includes 2 words of
<SRQR> and 1 word of <MTUR>.
(M7) Finally, Node1 sends data to Node2 using L2-forwarding.
0 1 2 3 4 5 6 7
+-----------------------------------------------------------------------+
| <---- The L2-header needed to get from Node1 to RouterB1 ----> |
| It may be any number of bytes. Here it is 11 bytes: 11230000000 |
+--------+--------+--------+--------+--------+--------+--------+--------+
|vv000000|10 L=4B | 3 | 0 | 3 | 0 | xxxx | xxxx |
+--------+--------+--------+--------+--------+--------+--------+--------+
|00 P |0 Node2 |Sensor.SubType=? | "Sensor" |
+---+----+--------+--------+--------+-+------+--------+--------+--------+
|E=3|PL=0| Data-Length=? (8B-words) |0| RZ |0 Node1 |
+---+----+--------+--------+--------+-+------+--------+--------+--------+
| |
| <------------------- The sensor data goes here ---------------------> |
| |
+--------+--------+--------+--------+--------+--------+--------+--------+
| 64 zero bits, unless any error was indicated along the path |
+--------+--------+--------+--------+--------+--------+--------+--------+
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E=3 (0b0011) indicates that all the data is 64-bit, Big Endian order.
All the messages shown in this appendix start with local L2 routing
bytes needed to get across either SAN1 or SAN2 (indicated with "The
L2-header needed to get from ... to ...") which are not L2RHs. The
difference is that these bytes are in front of the packet, exposed to
the local switches, whereas the L2RHs are only exposed to PacketWay-
entities.
These local L2 routing bytes are the actual bytes required by the
SANs and likely to be consumed as the messages traverses the SAN,
unlike the L2RHs that are intact until converted to actual routing
bytes.
The L2RHs start with 0bvv00000010 followed by the number of routing
bytes in that L2RH, and possibly also by several bytes of padding.
Glossary
Address A unique designation of a node (actually an
interface to that node) or a SAN.
Buddy-HR HRs are "buddies" if they are on the same SAN.
Cut-Through See Wormhole.
Destination The node to which a packet is intended.
Dynamic-Routing Routing according to dynamic information (i.e.,
acquired at run time, rather than pre-set).
Endianness The property of being Big-Endian or Little-Endian
(transmission order, etc.)
Ethertype A 16-bit value designating the type of Level-3
packets carried by a Level-2 communication sys-
tem.
HR Half-Router, the part of a router that handles
one network only.
L2-Forwarding Forwarding based on Level-2 (i.e., data-link
layer of the ISORM) information, e.g., the native
technique of each SAN or LAN. Also called
"source routing."
L3-Forwarding Forwarding based on end-to-end (Level-3 i.e.,
network layer of the ISORM) addresses. Also
called "destination routing."
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Map The topology of a network.
Mapper A node on a SAN/LAN that has the map and an RT
for that network. It is expected that the mapper
dynamically updates the map and the RT.
Multi-homed A node with more than one network interface,
where each interface has another address.
Node Whatever can send and receive packets (e.g., a
computer, an MPP, a software process, etc.)
Node A C-struct (or equivalent) containing values for
some attributes of a node.
Planned Transfer of information, occurs after an initial
phase in which the sender decides which Level-2
route to use for that transfer.
RCVF The "Received From" set includes all the physical
addresses through which an RT was disseminated,
starting with the address of the mapper that
created that RT.
Redirect A message that tells nodes which HR should be
used in order to get to a certain remote address.
Router The inter-SAN communication device.
Security A relationship between 2 (or more) nodes that
defines how the nodes utilize security services
to communicate securely.
Source The node that created a packet.
Source-Route A Level-2 route that is chosen for a packet by
its source.
Symbol Data preceding the EEP header of a PacketWay mes-
sage, interleaving with the L2RHs.
Twin-HR Two HRs are twins if they both are parts of the
same inter-SAN router.
Wormhole-routing (aka cut-thru routing) forwarding packets out of
switches as soon as possible, without storing
that entire packet in the switch (unlike Stop-
and-forward)
Zero-copy A TCP system that copies data directly between
the user area and the network device, bypassing
OS copies
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Acronyms and Abbreviations
0bNNNN The binary number NNNN (e.g., 0b0100 is 4-decimal)
0xNNNN The hexadecimal number NNNN (e.g., 0x0100 is 256-decimal)
8B 8 byte (64 bits) entity
ADDR The Address-record of RRP
AT Address Type
BER Bit Error Rate
CAPA The CAPAbility-record of RRP
CSR Common Source-Route
DA Destination Address
DB Data Block
DL Data Length (in 8B words)
DT Destination-Type
EEP End-to-End Protocol
EI Error Indication
GVL2 An RRP message, requesting L2 route to a given destination
GVRT An RRP message asking an HR to give its routing tables
HR Half Router
HRTO An RRP message asking which HR to use for a given destination
INFO An RRP message providing information about nodes
L2 Level-2 of the ISO Reference Model (Link)
L2RH Level-2 Routing Header
L2SR Source Route
L3 Level-3 of the ISO Reference Model (Network)
LADR The Logical-addresses-record of RRP
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LSbit Least Significant bit
LSbyte Least Significant byte
MSbit Most Significant bit
MSbyte Most Significant byte
MTU Maximum Transmission Unit
MTUR The MTU-record of RRP
NAME The name-record of RRP
OH Optional Header field
OH-TYPE The Type of an Optional Header field
Q Quality (of a path)
RCVF Received-From list, or the Received-From record of RRP
RDRC A re-direct message of RRP
RRP Router-to-Router Protocol
RTBL An RRP message proving a Routing Table
SRQR The Source-Route-and-Q-record of RRP
TELL RRP message requesting INFO about a partially specified node
UNK Unknown
WRU? An RRP message asking its recipient to identify itself
Editor's Address
Anthony Skjellum
Computer Science Department
Box 9637
Mississippi State University
Mississippi State, MS 39762-9637
Phone: 601-325-8435
Fax: 601-325-8997
Email: tony@cs.msstate.edu
Cohen et al. Experimental [Page 19]
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