diff --git a/src/lean_spec/subspecs/networking/config.py b/src/lean_spec/subspecs/networking/config.py
index d2011e4f..93b1740d 100644
--- a/src/lean_spec/subspecs/networking/config.py
+++ b/src/lean_spec/subspecs/networking/config.py
@@ -2,13 +2,15 @@
 
 from typing_extensions import Final
 
+from lean_spec.types.byte_arrays import Bytes4
+
 from .types import DomainType
 
 MAX_REQUEST_BLOCKS: Final = 2**10
 """Maximum number of blocks in a single request."""
 
-MESSAGE_DOMAIN_INVALID_SNAPPY: Final[DomainType] = b"\x00\x00\x00\x00"
+MESSAGE_DOMAIN_INVALID_SNAPPY: Final[DomainType] = Bytes4(b"\x00\x00\x00\x00")
 """4-byte domain for gossip message-id isolation of invalid snappy messages."""
 
-MESSAGE_DOMAIN_VALID_SNAPPY: Final[DomainType] = b"\x01\x00\x00\x00"
+MESSAGE_DOMAIN_VALID_SNAPPY: Final[DomainType] = Bytes4(b"\x01\x00\x00\x00")
 """4-byte domain for gossip message-id isolation of valid snappy messages."""
diff --git a/src/lean_spec/subspecs/networking/reqresp/message.py b/src/lean_spec/subspecs/networking/reqresp/message.py
index 5980b56c..440ee030 100644
--- a/src/lean_spec/subspecs/networking/reqresp/message.py
+++ b/src/lean_spec/subspecs/networking/reqresp/message.py
@@ -5,11 +5,10 @@
 domain. All messages are SSZ-encoded and then compressed with Snappy frames.
 """
 
-from pydantic import Field
-from typing_extensions import Annotated
+from typing import ClassVar, Type
 
 from lean_spec.subspecs.containers import Checkpoint, SignedBlockWithAttestation
-from lean_spec.types import Bytes32, StrictBaseModel
+from lean_spec.types import Bytes32, SSZList, SSZType, StrictBaseModel
 
 from ..config import MAX_REQUEST_BLOCKS
 from ..types import ProtocolId
@@ -67,24 +66,26 @@ class Status(StrictBaseModel):
 BLOCKS_BY_ROOT_PROTOCOL_V1: ProtocolId = "/leanconsensus/req/blocks_by_root/1/"
 """The protocol ID for the BlocksByRoot v1 request/response message."""
 
-BlocksByRootRequest = Annotated[
-    list[Bytes32],
-    Field(max_length=MAX_REQUEST_BLOCKS),
-]
-"""
-A request for one or more blocks by their root hashes.
 
-This is primarily used to recover recent or missing blocks from a peer.
-"""
+class BlocksByRootRequest(SSZList[Bytes32]):
+    """
+    A request for one or more blocks by their root hashes.
 
-BlocksByRootResponse = Annotated[
-    list[SignedBlockWithAttestation],
-    Field(max_length=MAX_REQUEST_BLOCKS),
-]
-"""
-A response containing the requested `SignedBlockWithAttestation` objects.
+    This is primarily used to recover recent or missing blocks from a peer.
+    """
 
-The length of the list may be less than the number of requested blocks if
-the responding peer does not have all of them. Each block is sent in a
-separate `response_chunk`.
-"""
+    ELEMENT_TYPE: ClassVar[Type[SSZType]] = Bytes32
+    LIMIT: ClassVar[int] = MAX_REQUEST_BLOCKS
+
+
+class BlocksByRootResponse(SSZList[SignedBlockWithAttestation]):
+    """
+    A response containing the requested `SignedBlockWithAttestation` objects.
+
+    The length of the list may be less than the number of requested blocks if
+    the responding peer does not have all of them. Each block is sent in a
+    separate `response_chunk`.
+    """
+
+    ELEMENT_TYPE: ClassVar[Type[SSZType]] = SignedBlockWithAttestation
+    LIMIT: ClassVar[int] = MAX_REQUEST_BLOCKS
diff --git a/src/lean_spec/subspecs/networking/types.py b/src/lean_spec/subspecs/networking/types.py
index 0aae6ab7..7cf4f12d 100644
--- a/src/lean_spec/subspecs/networking/types.py
+++ b/src/lean_spec/subspecs/networking/types.py
@@ -1,11 +1,22 @@
 """Networking-related type definitions for the specification."""
 
-from typing import Annotated
+from lean_spec.types import Uint64
+from lean_spec.types.byte_arrays import Bytes4, Bytes32
 
-from pydantic import Field
-
-DomainType = Annotated[bytes, Field(min_length=4, max_length=4)]
+DomainType = Bytes4
 """A 4-byte value used for domain separation in message-ids."""
 
+NodeId = Bytes32
+"""32-byte node identifier for Discovery v5, derived from ``keccak256(pubkey)``."""
+
 ProtocolId = str
 """A string representing a libp2p protocol ID."""
+
+SeqNumber = Uint64
+"""Sequence number used in ENR records, metadata, and ping messages."""
+
+SubnetId = Uint64
+"""Subnet identifier (0-63) for attestation subnet partitioning."""
+
+Multiaddr = str
+"""Multiaddress string, e.g. ``/ip4/192.168.1.1/tcp/9000``."""