ZyXEL Communications VMG8825-B Series Скачать руководство пользователя страница 79

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Chapter 6 Broadband

VMG8825-B Series User’s Guide

Encapsulation

Select the method of multiplexing used by your ISP from the drop-down list box. Choices are:

•

LLC/SNAP-BRIDGING:

In LCC encapsulation, bridged PDUs are encapsulated by identifying

the type of the bridged media in the SNAP header. This is available only when you select

IPoE

PPPoE

in the

Select DSL Link Type

field.

•

VC/MUX:

In VC multiplexing, each protocol is carried on a single ATM virtual circuit (VC). To

transport multiple protocols, the VMG needs separate VCs. There is a binding between a VC

and the type of the network protocol carried on the VC. This reduces payload overhead

since there is no need to carry protocol information in each Protocol Data Unit (PDU)

payload.

Service
Category

Select

UBR Without PCR

for applications that are non-time sensitive, such as e-mail.

Select

CBR

(Continuous Bit Rate) to specify fixed (always-on) bandwidth for voice or data traffic.

Select

Non Realtime VBR

(non real-time Variable Bit Rate) for connections that do not require

closely controlled delay and delay variation.

Select

Realtime VBR

(real-time Variable Bit Rate) for applications with bursty connections that

require closely controlled delay and delay variation.

Peak Cell

Rate [cells/s]

Divide the DSL line rate (bps) by 424 (the size of an ATM cell) to find the Peak Cell Rate (PCR). This
is the maximum rate at which the sender can send cells. Type the PCR here.

Sustainable

Cell Rate

The Sustain Cell Rate (SCR) sets the average cell rate (long-term) that can be transmitted. Type
the SCR, which must be less than the PCR. Note that system default is 0 cells/sec.

Maximum

Burst Size

[cells]

Maximum Burst Size (MBS) refers to the maximum number of cells that can be sent at the peak
rate. Type the MBS, which is less than 65535.

VLAN (These fields appear when the

Type

is set to

ADSL/VDSL over PTM

Active

Select

Enable

to activate VLAN on this WAN interface. Otherwise, select

Disable

to deactivate.

802.1p

IEEE 802.1p defines up to 8 separate traffic types by inserting a tag into a MAC-layer frame that
contains bits to define class of service.

Select the IEEE 802.1p priority level (from 0 to 7) to add to traffic through this connection. The
greater the number, the higher the priority level.

802.1q

Type the VLAN ID number (from 1 to 4094) for traffic through this connection.

MTU

Enter the MTU (Maximum Transfer Unit) size for this traffic.

Routing Feature (This is available only when you select

IPv4 Only

IPv4 IPv6 DualStack

in the

IPv4/IPv6 Mode

field.)

NAT Enable

Select this option to activate NAT on this connection.

Fullcone NAT
Enable

Select this option to enable full cone NAT on this connection. This field is available only when you
activate NAT. In full cone NAT, the VMG maps all outgoing packets from an internal IP address
and port to a single IP address and port on the external network. The VMG also maps packets
coming to that external IP address and port to the internal IP address and port.

IGMP Proxy
Enable

Internet Group Multicast Protocol (IGMP) is a network-layer protocol used to establish
membership in a Multicast group - it is not used to carry user data.

Select this option to have the VMG act as an IGMP proxy on this connection. This allows the VMG
to get subscribing information and maintain a joined member list for each multicast group. It can
reduce multicast traffic significantly.

Apply as Default
Gateway

Select this option to have the VMG use the WAN interface of this connection as the system
default gateway.

DNS Server (This is available only when you select

IPv4 Only

IPv4 IPv6 DualStack

in the

IPv4/IPv6 Mode

field.)

Select

Obtain DNS Info Automically

if you want the VMG to use the DNS server addresses

assigned by your ISP.