Next Hop Resolution Protocol

The Next Hop Resolution Protocol (NHRP) is an extension of the ATM ARP routing mechanism{{cite journal|last1=White|first1=P.P.|title=ATM switching and IP routing integration: the next stage in Internet evolution?|journal=IEEE Communications Magazine|date=April 1998|volume=36|issue=4|pages=79–83|doi=10.1109/35.667418|url=http://www.cl.cam.ac.uk/~jac22/otalks/atmipint.pdf|accessdate=18 June 2016}} that is sometimes used to improve the efficiency of routing computer network traffic over a non-broadcast, multiple access (NBMA) network.{{cite web|title=NHRP|url=http://www.cisco.com/c/en/us/td/docs/ios/12_4/ip_addr/configuration/guide/hadnhrp.html#wp1054887|website=Cisco|accessdate=17 June 2016}} It is defined in IETF RFC 2332,{{cite journal|last1=B.|first1=Cole|last2=J.|first2=Luciani|last3=N.|first3=Doraswamy|last4=D.|first4=Piscitello|last5=D.|first5=Katz|title=NBMA Next Hop Resolution Protocol (NHRP)|url=https://tools.ietf.org/html/rfc2332|website=tools.ietf.org|date=April 1998 |accessdate=17 June 2016}} and further described in RFC 2333.{{cite journal|last1=Cansever|first1=Derya H.|title=NHRP Protocol Applicability Statement|url=https://tools.ietf.org/html/rfc2333|website=tools.ietf.org|date=April 1998 |accessdate=17 June 2016}} It can be used by a sender to determine a route with the fewest hops to a receiver.{{cite web|last1=Rouse|first1=Margaret|title=What is Next Hop Resolution Protocol (NHRP)? - Definition from WhatIs.com|url=http://searchnetworking.techtarget.com/definition/Next-Hop-Resolution-Protocol|website=SearchNetworking|accessdate=17 June 2016}} The protocol differs from ARP-type protocols in that it allows routing optimization across multiple IP subnets.{{cite journal|last1=Luciani|first1=James V.|editor-first1=Seyhan |editor-first2=Indra |editor-last1=Civanlar |editor-last2=Widjaja |title=Next-hop resolution protocol|date=1 January 1997|journal=SPIE Proceedings|series=Broadband Networking Technologies |volume=3233|pages=161–165|doi=10.1117/12.290456|bibcode=1997SPIE.3233..161L |s2cid=21461973|url=http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=933004}} NHRP is implemented by means of next-hop servers across IP subnets.{{cite book|last1=Ahmad|first1=Khalid|title=Sourcebook of ATM and IP Internetworking|date=2 April 2004|publisher=John Wiley & Sons|isbn=9780471660941|page=360|url=https://books.google.com/books?id=BjeG2uAaNK4C&q=%22Next+Hop+Resolution+Protocol%22&pg=PA360|accessdate=18 June 2016|language=en}}

NHRP forms a part of the Multiprotocol Encapsulation over ATM (MPOA) protocol as described in RFC 2684.{{cite journal|last1=Dan|first1=Grossman|last2=Juha|first2=Heinanen|title=Multiprotocol Encapsulation over ATM Adaptation Layer 5|url=https://tools.ietf.org/html/rfc2684|website=tools.ietf.org|date=September 1999 }}{{cite book|last1=Newman|first1=P.|last2=Lyon|first2=T.|last3=Minshall|first3=G.|title=Proceedings of IEEE INFOCOM '96. Conference on Computer Communications |chapter=Flow labelled IP: A connectionless approach to ATM |date=1 March 1996|volume=3|pages=1251–1260 vol.3|doi=10.1109/INFCOM.1996.493071|isbn=0-8186-7293-5|s2cid=5482472|chapter-url=https://www.researchgate.net/publication/2615390|accessdate=18 June 2016}} It also plays a role in Cisco's Dynamic Multipoint Virtual Private Network. A limitation of NHRP is its inability to improve{{Clarify span||date=October 2023}} multicast protocols.