16ng Working Group S. Madanapalli
Internet-Draft Ordyn Technologies
Intended status: Standards Track Soohong D. Park
Expires: May 3, 2009 Samsung Electronics
S. Chakrabarti
IP Infusion
G. Montenegro
Microsoft Corporation
October 30, 2008
Transmission of IPv4 packets over IEEE 802.16's IP Convergence Sublayer
draft-ietf-16ng-ipv4-over-802-dot-16-ipcs-04.txt
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Abstract
IEEE 802.16 is an air interface specification for wireless broadband
access. IEEE 802.16 has specified multiple service specific
convergence sublayers for transmitting upper layer protocols. The
packet CS (Packet Convergence Sublayer) is used for the transport of
all packet-based protocols such as Internet Protocol (IP), IEEE 802.3
(Ethernet) and IEEE 802.1Q (VLAN). The IP-specific part of the
Packet CS enables the transport of IPv4 packets directly over the
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IEEE 802.16 MAC.
This document specifies the frame format, the Maximum Transmission
Unit (MTU) and address assignment procedures for transmitting IPv4
packets over the IP-specific part of the Packet Convergence Sublayer
of IEEE 802.16.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Typical Network Architecture for IPv4 over IEEE 802.16 . . . . 3
3.1. IEEE 802.16 IPv4 Convergence sub-layer support . . . . . . 4
4. IPv4-CS link in 802.16 Networks . . . . . . . . . . . . . . . 5
4.1. IPv4-CS link establishment . . . . . . . . . . . . . . . . 5
4.2. Frame Format for IPv4 Packets . . . . . . . . . . . . . . 6
4.3. Maximum Transmission Unit . . . . . . . . . . . . . . . . 7
5. Subnet Model and IPv4 Address Assignment . . . . . . . . . . . 8
5.1. IPv4 Unicast Address Assignment and Router Discovery . . . 8
5.2. Address Resolution Protocol . . . . . . . . . . . . . . . 9
5.3. IP Multicast Address Mapping . . . . . . . . . . . . . . . 9
6. Handling Multicast and Broadcast packets in IPv4 CS . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . . 11
Appendix A. Multiple Convergence Layers - Impact on Subnet
Model . . . . . . . . . . . . . . . . . . . . . . . . 12
Appendix B. Sending and Receiving IPv4 Packets . . . . . . . . . 12
Appendix C. Wimax IPCS MTU size . . . . . . . . . . . . . . . . . 13
Appendix D. Thoughts on handling multicast-broadcast IP
packets . . . . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
Intellectual Property and Copyright Statements . . . . . . . . . . 16
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1. Introduction
IEEE 802.16 [IEEE802_16] is a connection oriented access technology
for the last mile. The IEEE 802.16 specification includes the PHY
and MAC details. The MAC includes various convergence sublayers (CS)
for transmitting higher layer packets including IPV4 packets
[RFC5154].
The scope of this specification is limited to the operation of IPv4
over the IP-specific part of the packet CS (referred to as "IPv4 CS"
or simply "IP CS" in this document).
This document specifies a method for encapsulating and transmitting
IPv4 [RFC0791] packets over the IP CS of IEEE 802.16. This document
also specifies the MTU and address assignment method for the IEEE
802.16 based networks using IP CS.
This document also discusses ARP (Address Resolution Protocol) and
Multicast Address Mapping whose operation is similar to any other
point-to-point link model.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Terminology
The terminology in this document is based on the definitions in
[RFC5154].
3. Typical Network Architecture for IPv4 over IEEE 802.16
The network architecture follows what is described in [RFC5154] and
[RFC5121]. In a nutshell, each MS is attached to an Access Router
(AR) through a Base Station (BS), a layer 2 entity. The AR can be an
integral part of the BS or the AR could be an entity beyond the BS
within the access network. IPv4 packets between the MS and BS are
carried over a point-to-point MAC transport connection which has a
unique connection identifier (CID). The packets between BS and AR
are carried using L2 tunnel (typically GRE tunnel) so that MS and AR
are seen as layer 3 peer entities. At least one L2 tunnel is
required for each MS, so that IP packets can be sent to MSs before
they acquire IP addresses. From the layer 3 perspective, MS and AR
are connected by a point-to-point link. The figure below illustrates
the network architecture for convenience.
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+-----+ CID1 +------+ +-----------+
| MS1 |----------+| BS |----------| AR |-----Internet
+-----+ / +------+ +-----------+
. / ____________
. CIDn / ()__________()
+-----+ / L2 Tunnel
| MSn |-----/
+-----+
Figure 1: Typical Network Architecture for IPv4 over IEEE 802.16
The above network model serves as an example and is shown to
illustrate the point to point link between the MS and the AR. The L2
tunnel is not required if BS and AR are integrated into a single box.
3.1. IEEE 802.16 IPv4 Convergence sub-layer support
As described in [RFC5154] section 3.3., an IP specific subpart
classifier carries either IPv4 or IPv6 payloads. In this document,
we are focussing on IPv4 over IP Convergence sublayer.
The convergence sublayer maintains an ordered "classifier table".
Each entry in the classifier table includes a classifier and a target
CID. In case of IP convergence sub-layer, the base-station performs
the mapping between CID or service-flow ID and a corresponding GRE
key for a particular IP-CS session. Also the classification takes
place in Access Router based on the GRE key per service-flow and/or
IP-address of the MS.
The other classifiers in Packet CS are IPv6 CS and Ethernet CS
[RFC5154]. The classifiers used by IP CS, enable the differentiation
of IPv4 and IPv6 packets and their mapping to specific transport
connections over the air interface.
The figure below shows the IPv4 user payload over IP transport over
the packet CS of IEEE 802.16:
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+-------------------+
| IPv4 Payload |
+-------------------+
| GRE |
+-------------------+ +-------------------+
| IPv4 Payload | | IP |
+-------------------+ +-------------------+
| IP-specific | | BS-AR Layer 2 |
| part of Packet CS | | specific link |
|...................| | (Ex: Ethernet) |
| 802.16 MAC | | |
+-------------------+ +-------------------+
| PHY | | PHY |
+-------------------+ +-------------------+
(1) IPv4 over IP-CS (2) IPv4 in L3 GRE encapsulation
between MS and BS between Base-station and AR
Figure 2: IEEE 802.16 transport of IPv4 Packets from MS to AR
4. IPv4-CS link in 802.16 Networks
In this document we have defined IPv4 CS link as a point-to-point
link between the MS and the AR using a set of service flows
consisting of MAC transport connections between a MS and BS, and L2
tunnel(s) between between a BS and AR. It is recommended that a
tunnel be established between the AR and a BS based on 'per MS' or
'per service flow' (An MS can have multiple service flows each of
which are identified by a unique service flow ID). Then the
tunnel(s) for an MS, in combination with the MS's MAC transport
connections, forms a single point-to-point link. Each MS belongs to
a different link and is assigned an unique IPv4 address per
recommendations in [RFC4968]. In summary:
o IPv4-CS uses the IPv4 header fields to classify the packets and
map to appropriate CID.
o Point-to-point link between MS and AR is established.
4.1. IPv4-CS link establishment
In order to enable the sending and receiving of IPv4 packets between
the MS and the AR, the link between the MS and the AR via the BS
needs to be established. This section explains the link
establishment procedures following section 6.2 of [RFC5121]. Steps
1-4 are same as indicated in 6.2 of [RFC5121]. In step 5, support
for IPv4 is indicated. In step 6, an initial service flow is created
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that can be used for exchanging IP layer signaling messages, e.g.
address assignment procedures using DHCP.
The address assignment procedure depends on the MS mode - i,e.
whether it is acting as a Mobile IPv4 client or a Proxy Mobile IP
client or a Simple IP client. In the most common case, the MS
requests an IP address using DHCP.
4.2. Frame Format for IPv4 Packets
IPv4 packets are transmitted in Generic IEEE 802.16 MAC frames in the
data payloads of the 802.16 PDU ( see section 3.2 of [RFC5154] ).
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|H|E| TYPE |R|C|EKS|R|LEN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LEN LSB | CID MSB |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CID LSB | HCS |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 |
+- -+
| header |
+- -+
| and |
+- -+
/ payload /
+- -+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|CRC (optional) |
+-+-+-+-+-+-+-+-+
Figure 3: IEEE 802.16 MAC Frame Format for IPv4 Packets
H: Header Type (1 bit). Shall be set to zero indicating that it
is a Generic MAC PDU.
E: Encryption Control. 0 = Payload is not encrypted; 1 = Payload
is encrypted.
R: Reserved. Shall be set to zero.
C: CRC Indicator. 1 = CRC is included, 0 = 1 No CRC is included
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EKS: Encryption Key Sequence
LEN: The Length in bytes of the MAC PDU including the MAC header
and the CRC if present (11 bits)
CID: Connection Identifier (16 bits)
HCS: Header Check Sequence (8 bits)
CRC: An optional 8-bit field. CRC appended to the PDU after
encryption.
TYPE: This field indicates the subheaders (Mesh subheader,
Fragmentation Subheader, Packing subheader etc and special payload
types (ARQ) present in the message payload
4.3. Maximum Transmission Unit
The MTU value for IPv4 packets on an IEEE 802.16 link is
configurable. The default MTU for IPv4 packets over an IEEE 802.16
link SHOULD be 1500 bytes. In some deployments, BS and AR are
separate entities; an encapsulation may be used to transport IPv4
packets between the BS and AR. In those cases the overhead of
encapsulation may be considered in the link MTU configuration.
Note, if a deployment configures the 802.16 link MTU less than 1500,
then 1500 byte packets from the MS will be dropped at the link-layer
silently; the legacy IPv4 client implementations do not determine the
link MTU by default before sending packets, while the DHCP servers
are required to provide the MTU information only when requested.
Please see Appendix C. for the default MTU value in WiMAX [WMF]
deployed networks.
This document recommends that a deployment should ensure that no
packet loss happens at the L2 level over IPV4 CS link-MTU, due to
mismatch in default MTU and the configured link MTUs.
However, it is strongly recommended that an IPv4 CS client host
configure the link-MTU before initiating the IP-level packet
exchange. The following paragraph discusses different approaches
through which the IPv4 CS client finds out the available link-MTU
value. The discovery and configuration of a proper link MTU value
ensures adequate usage of the network bandwidth and resource.
o The IEEE is currently revising 802.16 (see 802.16Rev2 [802_16REV2]
) to reproduce capabilities to inform the Service Data Unit or MAC
MTU in the IEEE 802.16 SBC-REQ/SBC-RSP phase, such that future
IEEE 802.16 compliant clients can configure the negotiated MTU
size for IP-CS link. However, the implementation must communicate
the negotiated MTU value to the IP layer to adjust the IP Maximum
payload size for proper handling of fragmentation. Note that this
method is useful only when MS is directly connected to the BS.
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o Configuration and negotiation of MTU size at the network-layer by
using DHCP interface MTU option [RFC2132].
This document recommends that all future implementations of IPv4 and
IPv4-CS clients SHOULD implement DHCP interface MTU option [RFC2132]
in order to configure its interface MTU according to the access
network in order to maximize the capacity of the bandwidth of the
network. Thus the IPv4 stack should have capability to adjust the
MTU value based on the DHCP response.
In the absence of DHCP MTU configuration, the client node (MS) has
two alternatives: 1) use the default MTU (1500 bytes) or 2) determine
the MTU by the methods described in [802_16REV2].
Additionally, the clients are encouraged to run PMTU[RFC 1191] or
PPMTUD[RFC 4821]. However, PMTU mechanism has inherent problems of
packet loss due to ICMP messages not reaching the sender and IPv4
routers not fragmenting the packets due to DF bit being set in the IP
packet. The above mentioned path MTU mechanisms will take care of
the MTU size between the MS and its correspondent node across
different flavors of convergence layers in the WiMAX networks and
other types of IP networks.
5. Subnet Model and IPv4 Address Assignment
The Subnet Model recommended for IPv4 over IEEE 802.16 using IP CS is
based on the point-to-point link between MS and AR [RFC4968], hence
each MS shall be assigned an address with 32bit prefix-length or
subnet-mask. The point-to-point link between MS and AR is achieved
using a set of IEEE 802.16 MAC connections (identified by CIDs) and a
L2 tunnel (usually a GRE tunnel) per MS between BS and AR. If the AR
is co-located with the BS then the set of IEEE 802.16 MAC connections
between the MS and BS/AR represent the point-to- point connection.
5.1. IPv4 Unicast Address Assignment and Router Discovery
DHCP [RFC2131] SHOULD be used for assigning IPv4 address for the MS.
DHCP messages are transported over IEEE 802.16 MAC connection to and
from the BS and relayed to the AR. In case DHCP server does not
reside in the AR, the AR SHOULD implement DHCP relay Agent [RFC1542].
Please refer to the MTU section of this document for requirements of
DHCP interface-MTU option for the new IPv4 CS MS implementation.
Although DHCP is the recommended method of address assignment, it is
possible that the MS could be a pure Mobile-IPv4 [RFC3344] device or
Wimax Mobile-IPv4 client which will be offered an IP-address from its
home-network after success-ful Mobile-IP [RFC3344] registration. In
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such situation, the mobile-client implementation SHOULD use the
default link MTU in order to avoid any link-layer packet loss due to
larger than supported packet size in the IP CS link.
Router discovery messages [RFC1256] contain router solicitation and
router advertisements. The Router solicitation messages (multicast
or broadcast) are directly delivered to AR via BS from the MS through
the point-to-point link. The BS SHOULD map the all-router multicast
nodes or broadcast nodes for router discovery to the AR's IP-address
and delivered directly to the AR. Similarly for router-advertisement
to the all-node multicast nodes will be either unicasted to each MS
by the BS separately or put onto a multicast connection to which all
MSs are listening to. If no multicast connection exists, and the BS
does not have the capability to aggregate and de-aggregate the
messages from and to the MS hosts, then the AR implementation must
take care of sending unicast messages to the corresponding individual
MS hosts within the set of broadcast or multicast recipients.
However, this specification simply assumes that the multicast service
is provided. How the multicast service is implemented in IEEE 802.16
Packet CS network, is out of scope of this document.
The 'Next-hop' IP-address of the IP CS MS is always the IP-address of
the AR, because MS and AR are attached with a point-to-point link.
5.2. Address Resolution Protocol
The IP CS does not allow for transmission of ARP [RFC0826] packets.
Furthermore, in a point-to-point link model, address resolution is
not needed.
5.3. IP Multicast Address Mapping
IPv4 multicast packets are carried over the point-to-point link
between the AR and the MS (via the BS). The IPv4 multicast packets
are classified normally at the IP CS if the IEEE 802.16 MAC
connection has been setup with a multicast IP address as a
classification parameter for the destination IP address. The IPv4
multicast address may be mapped into multicast CID defined in IEEE
802.16 specification, but the mapping mechanism at the BS or
efficiency of using multicast CID as opposed to simulating multicast
by generating multiple unicast messages are out of scope of this
document. However, it has been studied that the use of multicast CID
for realizing multicast transmissions reduces transmission efficiency
when the multicast group is small, due to the nature of wireless
network(IEEE 802.16) [ETHCS].
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6. Handling Multicast and Broadcast packets in IPv4 CS
In the IP-CS link model, two different approaches can work - 1) BS
maps the multicast or Broadcast IP-addresses into different multicast
CIDs of the MSs or 2) AR maps the multicast IP-addresses to different
unicast IP-addresses and send the packets directly to each MS
separately.
However as mentioned earlier, handling a mechanism of multicast or
broadcast IP CS packets are out of scope of this document. Please
refer to Appendix section for some thoughts and suggestions.
7. Security Considerations
This document specifies transmission of IPv4 packets over IEEE 802.16
networks with IPv4 Convergence Sublayer and does not introduce any
new vulnerabilities to IPv4 specifications or operation. The
security of the IEEE 802.16 air interface is the subject of
[IEEE802_16]. In addition, the security issues of the network
architecture spanning beyond the IEEE 802.16 base stations is the
subject of the documents defining such architectures, such as WiMAX
Network Architecture [WMF].
8. IANA Considerations
This document has no actions for IANA.
9. Acknowledgements
The authors would like to acknowledge the contributions of Bernard
Aboba, Dave Thaler, Jari Arkko, Bachet Sarikaya, Basavaraj Patil,
Paolo Narvaez, and Bruno Sousa for their review and comments. The
working group members Burcak Beser, Wesley George, Max Riegel and DJ
Johnston helped shape the MTU discussion for IPv4 CS link. Thanks to
many other members of the 16ng working group who commented on this
document to make it better.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981.
[RFC0826] Plummer, D., "Ethernet Address Resolution Protocol: Or
converting network protocol addresses to 48.bit Ethernet
address for transmission on Ethernet hardware", STD 37,
RFC 826, November 1982.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997.
[RFC1542] Wimer, W., "Clarifications and Extensions for the
Bootstrap Protocol", RFC 1542, October 1993.
[RFC5121] Patil, B., Xia, F., Sarikaya, B., Choi, JH., and S.
Madanapalli, "Transmission of IPv6 via the IPv6
Convergence Sublayer over IEEE 802.16 Networks", RFC 5121,
February 2008.
[RFC5154] Jee, J., Madanapalli, S., and J. Mandin, "IP over IEEE
802.16 Problem Statement and Goals", RFC 5154, April 2008.
[RFC4968] Madanapalli, S., "Analysis of IPv6 Link Models for 802.16
Based Networks", RFC 4968, August 2007.
10.2. Informative References
[RFC1191] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191,
November 1990.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, March 2007.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[RFC4840] Aboba, B., Davies, E., and D. Thaler, "Multiple
Encapsulation Methods Considered Harmful", RFC 4840,
April 2007.
[RFC3344] Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
August 2002.
[RFC1256] Deering, S., "ICMP Router Discovery Messages", RFC 1256,
September 1991.
[ETHCS] Jeon, H., Riegel, M., and S. Jeong, "Transmission of IP
over Ethernet over IEEE 802.16 Networks", April 2008,
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<http://www.ietf.org/internet-drafts/
draft-ietf-16ng-ip-over-ethernet-over-802.16-06.txt>.
[802_16REV2]
Johnston, D., "SDU MTU Capability Declaration",
March 2008, <http://www.ieee.org/16>.
[IEEE802_16]
"IEEE 802.16e, IEEE standard for Local and metropolitan
area networks, Part 16:Air Interface for fixed and Mobile
broadband wireless access systems", October 2005.
[WMF] "WiMAX End-to-End Network Systems Architecture Stage 2-3
Release 1.2,
http://www.wimaxforum.org/technology/documents",
January 2008.
Appendix A. Multiple Convergence Layers - Impact on Subnet Model
Two different MSs using two different convergence sublayers (e.g. an
MS using Ethernet CS only and another MS using IP CS only) cannot
communicate at data link layer and requires interworking at IP layer.
For this reason, these two nodes must be configured to be on two
different subnets. For more information refer [RFC4840].
Appendix B. Sending and Receiving IPv4 Packets
IEEE 802.16 MAC is a point-to-multipoint connection oriented air-
interface, and the process of sending and receiving of IPv4 packets
is different from multicast capable shared medium technologies like
Ethernet.
Before any packets being transmitted, IEEE 802.16 transport
connection must be established. This connection consists of IEEE
802.16 MAC transport connection between MS and BS and an L2 tunnel
between BS and AR. This IEEE 802.16 transport connection provides a
point-to-point link between MS and AR. All the packets originated at
the MS always reach AR before being transmitted to the final
destination.
IPv4 packets are carried directly in the payload of IEEE 802.16
frames when the IPv4 CS is used. IPv4 CS classifies the packet based
on upper layer (IP and transport layers)header fields to put the
packet on one of the available connections identified by the CID.
The classifiers for the IPv4 CS are source and destination IPv4
addresses, source and destinations ports, Type-of-Service and IP
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protocol field. The CS may employ Packet Header Suppression (PHS)
after the classification.
The BS tunnels the packet that has been received on a particular MAC
connection to the AR. BS reconstructs the payload header if the PHS
is in use before the packet is tunneled to the AR. Similarly the
packets received on a tunnel interface from the AR, would be mapped
to a particular CID using IPv4 classification mechanism.
AR performs normal routing for the packets that it receives and
forwards the packet based on its forwarding table. However the DHCP
relay agent in the AR, MUST maintain the tunnel interface on which it
receives DHCP requests, so that it can relay the DHCP responses to
the correct MS. One way of doing this is to have a mapping between
MAC address and Tunnel Identifier.
Appendix C. Wimax IPCS MTU size
WiMAX (Worldwide Interoperability for Microwave Access) forum has
defined a network architecture[WMF] where IPV4 CS is supported for
transmission of IPV4 packets between MS and BS over the IEEE
802.16 link. The addressing and operation of IPV4CS described in
this document are applicable to the WiMAX networks as well. The
WiMAX forum [WMF] has specified the Max SDU size as 1522 octets.
However, it specifies that IP-payload in WiMAX architecture[WMF]
is 1400 bytes.
Hence if a IPV4-CS MS is configured with 1500 bytes it will have
to be communicated by the access router(AR) about the default link
MTU (1400 bytes) in WiMAX network. However, currently in IPv4
client architecture a node is not required to ask for MTU option
in its DHCP messages nor an IPv4 router-advertisement can inform
the node about the link MTU. An IPV4CS client is not capable of
doing ARP probing either to find out the link MTU. Thus current
specifications of WiMAX network access routers cannot communicate
its link MTU to the IPV4CS MS. On the other hand, it is
imperative for an MS to know the link MTU size if it is not the
default MTU value for de-facto standard in order to successfully
send packets in the network towards the first hop. Some
implementations with IEEE 802.16 layer 2 support, should be able
to sense IPV4CS WiMAX network and adjust their MTU size
accordingly, however this document does not make any assumptions on
this requirement.
Thus, WiMAX MS nodes should use this default (1400) MTU value per the
current specification [WMF]. However, due to reasons specified in
section 4.3 above, it is strongly recommended that future WiMAX MS
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nodes support a default MTU of 1500 bytes, and that they implement
MTU negotiation capabilities as mentioned in this document.
Appendix D. Thoughts on handling multicast-broadcast IP packets
Although this document does not directly specify details of multicast
or broadcast packet handling, here are some suggestions:
While uplink connections from the MSs to the BS provide only unicast
transmission capabilities, downlink connections can be used for
multicast transmission to a group of MSs as well as unicast
transmission from the BS to a single MS. For all-node IP-addresses,
the AR or BS should have special mapping and the packets should be
distributed to all active point-to-point connections by the AR or by
the BS. All-router multicast packets and any broadcast packets from
a MS will be forwarded to the AR by the BS. If BS and MS are co-
located, then the first approach is more useful. If the AR and BS
are located separately then the second approach SHOULD be
implemented. An initial capability exchange message should be
performed between BS and AR (if they are not co-located) to determine
who would perform the distribution of multicast/broadcast packets.
Such mechansim should be part of L2 exchange during the connection
setup and is out of scope of this document. In order to save energy
of the wireless end-devices in the IEEE 802.16 wireless network, it
is recommened that the multicast and broadcast from network side to
device side should be reduced. Only DHCP, IGMP, Router-advertisemnet
packets are allowed on the downlink for multicast and broadcast IP-
addresses. Other protocols using multicast and broadcast IP-
addresses should be permitted through local AR/BS configuration.
Authors' Addresses
Syam Madanapalli
Ordyn Technologies
1st Floor, Creator Building, ITPL
Bangalore - 560066
India
Email: smadanapalli@gmail.com
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Soohong Daniel Park
Samsung Electronics
416 Maetan-3dong, Yeongtong-gu
Suwon 442-742
Korea
Email: soohong.park@samsung.com
Samita Chakrabarti
IP Infusion
1188 Arques Avenue
Sunnyvale, CA
USA
Email: samitac@ipinfusion.com
Gabriel Montenegro
Microsoft Corporation
Redmond, Washington
USA
Email: gabriel.montenegro@microsoft.com
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