Adjust the TCP maximum segment size (MSS) to improve the throughput for the TCP session over a Fabric Extend (FE) adjacency. By default, this functionality is enabled and auto-derived.

Adjust the TCP Maximum Segment Size

Note

Note

This procedure only applies to XA1400 Series.

Adjust the TCP maximum segment size (MSS) to improve the throughput for the TCP session over a Fabric Extend (FE) adjacency. By default, this functionality is enabled and auto-derived.

Tip

Tip

As a best practice, turn off this enhancement on the head-end side and keep this enabled only at the branch side.

About this task

The MSS adjustment functionality only activates when at least one FE tunnel with a maximum transmission unit (MTU) greater than or equal to 1500 is configured. The functionality is inactive if no FE tunnels with MTU greater than or equal to 1500 are configured. Deleting the last tunnel with MTU greater than or equal to 1500 results in the functionality becoming inactive.

The switch can auto-derive the MSS value based of the tunnel MTUs or you can manually configure the MSS value. The formula for the auto-derived value is min(Tunnels MTUs) - 250B (size for VXLAN + MIM + IPSEC + IP+TCP headers). If you configure multiple FE tunnels with MTU greater than or equal to 1500, then the switch uses the lowest of all tunnel MTUs to auto-derive the TCP MSS adjust value. The same value applies to all TCP syn packets that transmit NNI to UNI and UNI to NNI.

The switch does not support different TCP adjust MSS values if you configure different FE tunnel MTUs on different tunnels.

If you configure FE tunnels and regular NNIs on the same adjacency, then the TCP adjust MSS value applies to all TCP packets traversing across regular NNIs and FE tunnels.

Procedure

  1. In the navigation pane, expand Configuration > IS-IS > .
  2. Select IS-IS.
  3. Select the Globals tab.
  4. Select the TcpAdjustMssEnable field to enable this functionality.
  5. Optional: Enter a value in the TcpAdjustMssValue field.
  6. Select Apply.

Globals Field Descriptions

Use the data in the following table to use the Globals tab.

Name

Description

AdminState

Specifies the global status of IS-IS on the switch: on or off. The default is off.

LevelType

Sets the router type globally:

  • level1: Level-1 router type

  • level1and2: Level–1/2 router type is not supported.

The default value is level1.

SystemId

Specifies the IS-IS system ID for the switch. Valid value is a 6–byte value in the format <xxxx.xxxx.xxxx>.

Important:

After you have configured the SPBM nickname and enabled IS-IS, if you require a change of the system ID, you must also change the nickname. However, for naming convention purposes or configuration purposes, you may not want to change the nickname. To maintain the same nickname with a different system ID, see Job aid.

MaxLspGenInt

Specifies the maximum interval, in seconds, between generated LSPs by this Intermediate system. The value must be greater than any value configured for RxmtLspInt.

The default value is 900 seconds.

CsnpInt

Specifies the Complete Sequence Number Packet (CSNP) interval in seconds. This is a system level parameter that applies for L1 CSNP generation on all interfaces.

The default value is 10.

RxmtLspInt

Specifies the minimum time between retransmission of an LSP. This defines how fast the switch resends the same LSP. This is a system level parameter that applies for L1 retransmission of LSPs.

The default value is 5 seconds.

PSNPInterval

Specifies the Partial Sequence Number Packet (PSNP) interval in seconds. This is a system level parameter that applies for L1 PSNP generation on all interfaces.

The default value is 2.

SpfDelay

Specifies the SPF delay in milliseconds. This value is used to pace successive SPF runs. The timer prevents two SPF runs from being scheduled very closely.

The default value is 100 milliseconds.

HostName

Specifies a name for the system. This may be used as the host name for dynamic host name exchange in accordance with RFC 2763.

By default, the system name comes from the host name configured at the system level.

IpSourceAddress

Specifies IP source address for SPBM IP shortcuts.

Ipv6SourceAddressType

Click ipv6 to use IPv6 addresses.

Ipv6SourceAddress

Specifies IPv6 source address for SPBM IP shortcuts.

IpTunnelSourceAddress

Specifies the IS-IS IP tunnel source address.

IpTunnelVrf

Specifies the VRF name associated with the IP tunnel.

MgmtIpAddr

Specifies the DvR management IP address for this node, in the DvR domain.

BackboneEnable

Select to enable this node to join the DvR backbone so that it can receive redistributed DvR host routes from all DvR Controllers in the network.

FanMember

Specifies whether the node is a member of the Fabric Area Network (FAN) .

DynamicallyLearnedArea

For FAN members, specifies the IS-IS area that is dynamically learned from the neighbor‘s Hello PDU if the node does not have the IS-IS manual area configured.

TcpAdjustMssEnable

Note:

Exception: Only supported on XA1400 Series.

Adjusts the TCP maximum segment size (MSS) to improve the throughput for the TCP session over a Fabric Extend (FE) adjacency. By default, this functionality is enabled and auto-derived.

TcpAdjustMssStatus

Note:

Exception: Only supported on XA1400 Series.

Displays the activation status of the MSS adjustment functionality. The MSS adjustment functionality only activates when at least one FE tunnel with a maximum transmission unit (MTU) greater than or equal to 1500 is configured.

TcpAdjustMssType

Note:

Exception: Only supported on XA1400 Series.

Displays if the MSS adjustment value is manually configured or auto-derived.

TcpAdjustMssValue

Note:

Exception: Only supported on XA1400 Series.

Configures the MSS adjustment value.
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