Multicast Path MTU
draft-nandy-utkarsh-pim-mcast-path-mtu-00
INTERNET-DRAFT Tathagata Nandy
Intended Status: Proposed Standard HPE
Utkarsh Srivastava
HPE
Expires: 18 July 2021 January 18, 2021
Multicast Path MTU
draft-nandy-utkarsh-pim-mcast-path-mtu-00
Abstract
Path MTU discovery (rfc1191) is a standard technique to determine
the supported MTU between two Internet Protocol (IP) hosts to avoid
any fragmentation. In a multicast distribution tree, source will
not know where the receivers are located. So the technique used to
compute the path MTU for a unicast stream does not work in a
multicast network. This document describes a method to discover
multicast path MTU with the goal to avoid traffic loss. This
solution also aims to solve the problem of traffic loss in for
multicast streams because of incorrect MTU setting and no path MTU
support for multicast networks.
Status of This Memo
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This Internet-Draft will expire on 18 July 2021.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . 3
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . 4
4. Multicast Path MTU . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . 6
6. IANA considerations . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . 7
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
When one IP host has a large amount of data to send to another
host, the data is transmitted as a series of IP datagrams. It is
usually preferable that these datagrams be of the largest size that
does not require fragmentation anywhere along the path from the
source to the destination. (For the case against fragmentation,
see [5].) This datagram size is referred to as the Path MTU (PMTU),
and it is equal to the minimum of the MTUs of each hop in the path.
A shortcoming of the current Internet protocol suite is the lack of
a standard mechanism for a host to discover the PMTU of an
arbitrary path. Note: The Path MTU is what in [1] is called the
"Effective MTU for sending" (EMTU_S). A PMTU is associated with a
path, which is a particular combination of IP source and
destination address and perhaps a Type-of-service (TOS). The
current practice [1] is to use the lesser of 576 and the first-hop
MTU as the PMTU for any destination that is not connected to the
same network or subnet as the source. In computer networking,
multicast is group communication where data transmission is
addressed to a group of destination computers simultaneously.
Multicast can be one-to-many or many-to-many distribution.
Multicast should not be confused with physical layer
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