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BITSTRING BASED PATH/DOMAIN MTU DISCOVERY IN BIT INDEX EXPLICIT REPLICATION (BIER) ENVIRONMENT

IP.com Disclosure Number: IPCOM000247401D
Publication Date: 2016-Sep-01
Document File: 4 page(s) / 222K

Publishing Venue

The IP.com Prior Art Database

Related People

Nagendra Kumar Nainar: AUTHOR [+3]

Abstract

Each node within a Bit Index Explicit Replication (BIER) domain advertises the link maximum transmission unit (MTU) through the Internal Gateway Protocol (IGP). Each Bit Forwarding Ingress Router (BFIR) calculates the lowest link MTU within the BIER domain, create a virtual BIER interface (BIERvif) and assign the calculated MTU as an egress MTU. This interface is the default forwarding interface for BIER encapsulated packets, and is referred to as the Primary BIERvif.

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Page 01 of 4

BITSTRING BASED PATH/DOMAIN MTU DISCOVERY IN BIT INDEX EXPLICIT REPLICATION (BIER) ENVIRONMENT

AUTHORS:

Nagendra Kumar Nainar Carlos M. Pignataro

Neale Ranns

CISCO SYSTEMS, INC.

ABSTRACT

    Each node within a Bit Index Explicit Replication (BIER) domain advertises the link maximum transmission unit (MTU) through the Internal Gateway Protocol (IGP). Each Bit Forwarding Ingress Router (BFIR) calculates the lowest link MTU within the BIER domain, create a virtual BIER interface (BIERvif) and assign the calculated MTU as an egress MTU. This interface is the default forwarding interface for BIER encapsulated packets, and is referred to as the Primary BIERvif.

DETAILED DESCRIPTION

     Bit Index Explicit Replication (BIER) is a stateless replication architecture that follows a unicast path. The nature of defining the receiver set as BitString in BIER header makes it possible to tackle various challenges associated with Internet Protocol (IP) multicast. One of the challenges/behaviors with IP multicast is that the maximum transmission unit (MTU) of a stream is the minimum path MTU of all the receivers. This puts a burden on all receivers/egress for re-assembly.

    With BIER being a new header, there are concerns about the behavior if the packet is more than the egress MTU. An active probe based approach may be used to query the path MTU along the path to a different Bit Forwarding Ingress Router (BFIR) and split the receiver set based on MTU. This has been documented in draft-mirsky-bier- path-mtu-discovery. This approach is inefficient and has many challenges.

    Presented herein is a solution that is easy to implement and can be optimized in a very scalable manner. The solution is as follows. Each node within a BIER domain will advertise the link MTU through the Internal Gateway Protocol (IGP).

Copyright 2016 Cisco Systems, Inc.

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Each BFIR will calculate the lowest link MTU within the BIER domain, create a virtual BIER interface (BIERvif) and assign the calculated MTU as an egress MTU. This interface will be the default forwarding interface for BIER encapsulated packets, and is referred to as the Primary BIERvif.

    Any BFIR, upon receiving any out-of-band (OOB) join for S,G will initially use the MTU of the Primary BIERvif for BIER encapsulated packet forwarding.

    The BFIR, in addition, will query the database (local or PCE) with BitString for each stream to identify the lowest MTU for a specific BitString. The l...