# US 2015/0146531 A1 · Adaptive MTU size optimization using IGP > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2015/0146531 A1 - Document ID: US20150146531A1 - Status: Published application - Kind: A1 - Application number: 14/409,951 - Filed: 2012-06-21 - Published: 2015-05-28 - Earliest claimed: 2012-06-21 - Assignees: Telefonaktiebolaget L M Ericsson (publ) - Inventors: Annikki Welin; Tomas Thyni; Johan Kölhi; Lars Hallström - Web page: https://patentgrep.com/patent/US20150146531A1 ## CPC - H04L 47/36: by determining packet size, e.g. maximum transfer unit [MTU] - H04L 45/03: by updating link state protocols - H04L 45/74: Address processing for routing - H04L 47/365: {Dynamic adaptation of the packet size} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract The present invention relates to methods and routing and/or switching devices for determining a path maximum transmission unit MTUP(n) size for transmission paths between edge nodes in a data communications network and for updating routing tables associated with the routing and/or switching devices in said edge nodes, which are linked together with link interfaces L(i) constituting transmission paths P(n) for data packet transmission, each link interface L(i) having a link interface maximum transmission unit MTUL(i) size. The methods involve the acquisition of a link interface maximum transmission unit MTUL(i) size for a link interface L(i), and the updating the routing table by calculating the path maximum transmission unit MTUP(n) size for each destination that involves the link interface L(i) for the acquired link interface maximum transmission unit MTUL(i) size. New link-state protocols for distributing the link interface maximum transmission unit MTUL(i) size is also provided. ## Claims ### Claim 1 A method for determining a path maximum transmission unit size for transmission paths between edge nodes in a data communications network and for updating routing tables associated with routing and/or switching devices in said edge nodes, which are linked together with link interfaces constituting transmission paths for data packet transmission, each link interface having a link interface maximum transmission unit size, said method comprising: acquiring a link interface maximum transmission unit size for a link interface; updating the routing table by calculating the path maximum transmission unit size for each destination that involves the link interface for the acquired link interface maximum transmission unit size. ### Claim 2 (depends on 1) The method according to claim 1, wherein the updating step further comprises: calculating and selecting for each one of said destinations the lowest link interface maximum transmission unit size of the link interfaces constituting a transmission path to said destination as the calculated maximum transmission unit size. ### Claim 3 (depends on 1) The method according to claim 1, wherein the updating step further comprises the step of: storing the calculated maximum transmission unit size for the destination in the routing table. ### Claim 4 (depends on 1) The method according to claim 1, wherein the acquiring step further comprises the step of: acquiring maximum transmission units size for a link interface from a received link-state protocol message, if a link-state routing protocol message is received. ### Claim 5 (depends on 1) The method according to claim 1, wherein the method further comprises the step of: generating and forwarding a link-state routing protocol message comprising the link interface maximum transmission unit size to one or more of the edge nodes in the data communications network. ### Claim 6 (depends on 4) The method according to claim 4, wherein the link-state protocol message is an Intermediate System to Intermediate System (IS-IS) protocol message comprising the maximum transmission unit size for a link as a Type-Length-Value (TLV). ### Claim 7 (depends on 4) The method according to claim 4, wherein the received link-state protocol message is an Open Shortest Path First, OSPF, protocol message comprising the maximum transmission unit size for a link as a Link-State Advertisement (LSA) type value. ### Claim 8 (depends on 1) The method according to claim 1, wherein the method comprises the step of: receiving data packets addressed to a destination within said data communication network; acquiring from the routing table the lowest link interface maximum transmission unit size of the link interfaces constituting a transmission path to said destination, said lowest link interface maximum transmission unit size of the link interfaces constituting a transmission path representing the path maximum transmission unit size for the destination; configuring the routing and/or switching device to send data packets not larger than the lowest link interface maximum transmission unit size of the link interfaces constituting a transmission path to said destination; forwarding the data packets addressed to said destination. ### Claim 9 (canceled) ### Claim 10 (canceled) ### Claim 11 A routing and/or switching device controller arrangement for determining a path maximum transmission unit size for transmission paths between edge nodes in a data communications network and for updating routing tables associated with routing and/or switching devices in said edge nodes, which are linked together with link interfaces constituting transmission paths for data packet transmission, each link interface having a link interface maximum transmission unit size, said arrangement comprising: acquisition means configured to acquire a link interface maximum transmission unit size; and routing table updating means configured to update the routing table, said routing table updating means comprises calculating means configured to calculate the path maximum transmission unit size for each destination that involves the link interface for the acquired link interface maximum transmission unit size. ### Claim 12 (depends on 11) The arrangement according to claim 11, wherein the calculating means is further configured to calculate and select for each one of said destinations the lowest link interface maximum transmission unit size of the link interfaces constituting a transmission path to said destination as the calculated maximum transmission unit size. ### Claim 13 (depends on 11) The arrangement according to claim 11, wherein the routing table updating means is configured to store the calculated maximum transmission unit size for the destination in the routing table. ### Claim 14 (depends on 11) The arrangement according to claim 11, wherein the acquisition means further is configured to acquire maximum transmission units size for a link interface from a received link-state protocol message, if a link-state routing protocol message is received by the routing and/or switching device controller arrangement. ### Claim 15 (depends on 11) The arrangement according to claim 11, wherein the arrangement comprises a message generator configured to generate and forward a link-state routing protocol message comprising the link interface maximum transmission unit size to one or more of the edge nodes in the data communications network. ### Claim 16 (depends on 14) The arrangement according to claim 14, wherein the link-state protocol message is an Intermediate System to Intermediate System (IS-IS) protocol message comprising the maximum transmission unit size for a link as a Type-Length-Value (TLV). ### Claim 17 (depends on 14) The arrangement according to claim 14, wherein the link-state protocol message is an Open Shortest Path First (OSPF) protocol message comprising the maximum transmission unit size for a link as a Link-State Advertisement (LSA) type value.