As per Relevance of the word hardware, we have this rfc below:
Network Working Group K.
Request for Comments: 2176 M.
Category: Informational NTT
June 1997
IPv4 over MAPOS Version 1
Status of this
This memo provides information for the Internet community. This
does not specify an Internet standard of any kind. Distribution
this memo is unlimited
Authors'
This memo documents a mechanism for supporting Version 4 of
Internet Protocol (IPv4) on Version 1 of the Multiple Access
over SONET/SDH. This document is NOT the product of an IETF
group nor is it a standards track document. It has not
benefited from the widespread and in-depth community review
standards track documents receive
This document describes a protocol for transmission of the
Protocol Version 4 (IPv4) over Multiple Access Over SONET/SDH (MAPOS
version 1. MAPOS is a link layer protocol and provides
access capability over SONET/SDH links. IP runs on top of MAPOS.
document explains IP datagram encapsulation in HDLC frame of MAPOS
and the Address Resolution Protocol (ARP).
1.
Multiple Access Protocol over SONET/SDH (MAPOS) [1] is a high-
link-layer protocol that provides multiple access capability
SONET/SDH. Its frame format is based on the HDLC-like framing [2]
PPP. A component called "Frame Switch" [1] allows multiple nodes
be connected together in a star topology to form a LAN. Using
haul SONET/SDH links, the nodes on such a "SONET-LAN" can span over
wide geographical area. The Internet Protocol (IP) [3] datagrams
transmitted in MAPOS HDLC frames [1].
This document describes a protocol for transmission of IP
over MAPOS version 1 [1]. It explains IP datagram encapsulation
HDLC frame of MAPOS, and ARP (Address Resolution Protocol)
mapping between IP address and HDLC address
Murakami & Maruyama Informational [Page 1]
RFC 2176 MAPOS June 1997
2. Frame Format for Encapsulating IP
An IP datagram is transmitted in a MAPOS HDLC frame. The
field of the frame must contain the value 0x0021 (hexadecimal)
defined by the "MAPOS Version 1 Assigned Numbers" [4].
information field contains the IP datagram
The information field may be one to 65,280 octets in length;
MTU(Maximum Transmission Unit) of MAPOS is 65,280 octets.
the large MTU size can suppress the overhead of IP header processing
it may cause fragmentation anywhere along the path from the source
the destination and result in performance degradation. To cope
the issue, Path MTU discovery [5] may be used
3. Address
This section explains MAPOS ARP and the mapping of special addresses
3.1 ARP
Each node on a MAPOS network maintains an "ARP cache" that
destination IP addresses to their corresponding 8-bit HDLC addresses
Entries are added to this cache either manually or by the
Resolution Protocol described below. Entries are removed from
cache manually, by the UNARP mechanism, or by ARP cache
mechanism. An implementation must provide a mechanism for
adding or removing arbitrary ARP cache entries
3.2 Address Resolution Protocol (ARP
This subsection describes MAPOS ARP protocol and its packet format
3.2.1
The MAPOS ARP is similar to that for ethernet. Prior to sending
IP datagram, the node must know the destination HDLC
corresponding to the destination IP address. When its ARP cache
not contain the corresponding entry, it uses ARP to translate the
address to the HDLC address. That is, it broadcasts an ARP
containing the destination IP address. In response to the request
the node which has the IP address sends an ARP reply containing
HDLC address. The returned HDLC address is stored in the ARP cache
3.2.2 ARP Frame
The protocol field for an ARP frame must contain 0xFE01 (hexadecimal
as defined by the "MAPOS Version 1 Assigned Numbers" [4].
information field contains the ARP packet as shown below
Murakami & Maruyama Informational [Page 2]
RFC 2176 MAPOS June 1997
+-------------------------+------------------------+
| Hardware Address Space | Protocol Address Space |
| (25:MAPOS) | (2048 in Dec) |
| 16 bits | 16 bits |
+------------+------------+------------------------+
| Hard Addr | Proto Addr | Operation Code |
| Length (4) | Length (4) |(1:Request 2:Response) |
| 8 bits | 8 bits | 16 bits |
+------------+------------+------------------------+
| Sender HDLC Address 32 bits |
+--------------------------------------------------+
| Sender IP Address 32 bits |
+--------------------------------------------------+
| Target HDLC Address 32 bits |
+--------------------------------------------------+
| Target IP Address 32 bits |
+--------------------------------------------------+
Figure 5 ARP packet
Hardware Address Space (16 bits
The hardware address space for MAPOS ARP is 25 in Decimal
assigned by IANA [6].
Protocol Address Space (16 bits
The protocol address space for IP is 2048 in Decimal
Hardware Address Length (8 bits
The hardware address length is 4.
Protocol Address Length (8 bits
The protocol address length for IP is 4.
Operation Code (16 bits
The operation code is 1 for request and 2 for response
Sender hardware (HDLC) Address (32 bits
Contains the sender's HDLC address in an ARP request, and
target HDLC address in an ARP response. The 8-bit HDLC address
placed in the least significant place of the 32-bit field.
remaining bits should be zero
Murakami & Maruyama Informational [Page 3]
RFC 2176 MAPOS June 1997
Sender Protocol (IP) Address (32 bits
Contains the sender's IP address in an ARP request, and the
IP address in an ARP response
Target hardware (HDLC) Address (32 bits
Contains unknown target HDLC address (all zeros) in an ARP request
and sender's HDLC address in an ARP response. The 8-bit
address is placed in the least significant place of the 32-
field. The remaining bits should be zero
Target Protocol (IP) Address (32 bits
Contains the target IP address in an ARP request, and the sender'
IP address in an ARP response
3.3
An implementation MUST provide an UNARP mechanism to flush
ARP cache entries. The mechanism is similar to the ARP
described in [7]. When a node detects that its port has came up,
MUST broadcast an UNARP packet. It forces every other node to
the obsolete ARP entry which was created by the node
connected to the switch port. An UNARP is an ARP clear request
the following values
Hardware Address Space : 25
Protocol Address Space : 2048
Hardware Address Length : 4
Protocol Address Length : 4
Operation Code : 23 (MAPOS-UNARP
Sender hardware (HDLC) Address : HDLC address of the
Sender Protocol (IP) Address : IP address of the
Target hardware (HDLC) Address : all 1
Target Protocol (IP) Address : 255.255.255.255 (broadcast
Hardware Address Space (16 bits
The hardware address space for MAPOS ARP is 25 in Decimal
assigned by IANA [6].
Operation Code (16 bits
The operation code is 23 for MAPOS-UNARP in Decimal as assigned
IANA [6].
Murakami & Maruyama Informational [Page 4]
RFC 2176 MAPOS June 1997
The node MUST send three UNARP packets at 30 seconds intervals.
receiving node of the packet MUST clear the ARP cache
associated with the Sender Protocol (IP) Address, if and only if
corresponding Hardware (HDLC) Address is not equal to that
in the UNARP packet. That is, if both the Sender Hardware (HDLC
Address and the Sender Protocol(IP) Address match those of the
entry, the entry is left unchanged
3.4 ARP Cache
An implementation MUST provide a mechanism to remove out-of-
cache entries and it SHOULD provide options to configure the
value [8]. One approach is to periodically time-out the
entries, even if they are in use. This approach involves ARP
timeouts in the order of a minute or less
Furthermore, when the link is lost on an interface, all ARP
entries associated with the interface MUST be removed immediately
Causes for link loss includes conditions such as loss of carrier
out-of-synchronization
3.5 IP Broadcast and
In broadcast and multicast frames, the most significant bit of
HDLC address must be 1 [1]. In addition, the least significant
must always be 1 to indicate the end of the field [1].
In the case of IP broadcast, the remaining six bits of the
address must be all 1s. That is, it should be mapped to the
broadcast address 0xFF (hexadecimal).
In the case of IP multicast, the remaining six bits of the
address must contain the lowest-order six bits of the IP
group address. It resembles IP multicast extension for
described in [9]. Exceptions arise when these six bits are
all zeros or all ones, in which case they should be altered to
bit sequence 111110.
4. Security
Security issues are not discussed in this memo
Murakami & Maruyama Informational [Page 5]
RFC 2176 MAPOS June 1997
[1] Murakami, K. and M. Maruyama, "MAPOS - Multiple Access
over SONET/SDH, Version 1," RFC-2171, June 1997.
[2] Simpson, W., editor, "PPP in HDLC-like Framing," RFC-1662,
July 1994.
[3] Postel, J., "Internet Protocol (IP)," RFC-791, September 1981.
[4] Maruyama, M. and K. Murakami, "MAPOS Version 1
Numbers," RFC-2172, June 1997.
[5] Mogul, J. and S. Deering, "Path MTU Discovery," RFC-1191,
Nov. 1990.
[6] IANA, "IANA-Assignments",
http://www.iana.org/iana/assignments.
[7] Malkin, G., "ARP Extension - UNARP," RFC-1868, November 1995.
[8] Braden, R., "Requirements for Internet Hosts -
Layers," RFC-1122, October 1989.
[9] Deering, S., "Host Extensions for IP Multicasting," RFC-1112,
August 1989.
The authors would like to acknowledge the contributions
thoughtful suggestions of John P. Mullaney, Clark Bremer,
Kobayashi, Paul Francis, Toshiaki Yoshida, and Takahiro Sajima
Author's
Ken
NTT Software
3-9-11, Midori-
Musashino-
Tokyo-180,
E-mail: murakami@ntt-20.ecl.
Mitsuru
NTT Software
3-9-11, Midori-
Musashino-
Tokyo-180,
E-mail: mitsuru@ntt-20.ecl.
Murakami & Maruyama Informational [Page 6]
if you see any problems within the linking, don't worry be happy,
this is version 0.1 of the Relevance System and you gotta expect some crappy subroutines sometimes,
just be content we did not write this in Java, which would have made this "bigger and better" HAHAHHA.
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